INTERNET-DRAFT R. W. Shirey
Obsoletes: RFC 2828 (if approved) BBN Technologies
Expiration Date: 20 February 2004 20 August 2004
Internet Security Glossary, Version 2
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Abstract
This Glossary has 1,500 entries that give definitions, abbreviations,
and explanations for terminology concerning information system
security. It makes recommendations to improve the clarity of Internet
Standards documents (ISDs) and the ease with which international
readers can understand ISDs. Its follow the principles that ISDs
should (a) use the same term or definition whenever the same concept
is mentioned; (b) use terms in their plainest, dictionary sense; (c)
use terms that are already well-established in open publications; and
(d) avoid terms that are proprietary, favor a particular vendor, or
create a bias toward a particular technology or mechanism versus
other, competing techniques that already exist or might be developed.
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Table of Contents
Section Page
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1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Format of Entries . . . . . . . . . . . . . . . . . . . . . . 4
2.1 Presentation Order . . . . . . . . . . . . . . . . . . . . 4
2.2 Capitalization and Abbreviation . . . . . . . . . . . . . 4
2.3 Support for Automated Searching . . . . . . . . . . . . . 5
2.4 Definition Type and Context . . . . . . . . . . . . . . . 5
2.5 Explanatory Notes . . . . . . . . . . . . . . . . . . . . 5
2.6 Cross-References . . . . . . . . . . . . . . . . . . . . . 5
2.7 Trademarks . . . . . . . . . . . . . . . . . . . . . . . . 6
2.8 The New Punctuation . . . . . . . . . . . . . . . . . . . 6
3. Types of Definitions . . . . . . . . . . . . . . . . . . . . . 6
3.1 Type "I": Recommended Definition with Internet Basis . . . 6
3.2 Type "N": Recommended Definition with Non-Internet Basis . 7
3.3 Type "O": Other Definitions. . . . . . . . . . . . . . . . 7
2.4 Type "D": Deprecated Definitions . . . . . . . . . . . . . 7
2.5 Definition Substitutions . . . . . . . . . . . . . . . . . 7
4. Definitions . . . . . . . . . . . . . . . . . . . . . . . . . 9
5. Informative References . . . . . . . . . . . . . . . . . . . 276
6. Security Considerations . . . . . . . . . . . . . . . . . . . 293
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 293
8. Author's Address . . . . . . . . . . . . . . . . . . . . . . . 293
9. Full Copyright Statement . . . . . . . . . . . . . . . . . . . 293
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1. Introduction
This Glossary provides an internally consistent and self-contained
set of terms, abbreviations, and definitions -- supported by
explanations, recommendations, and references -- for terminology that
concerns information system security. The intent of this Glossary is
to improve the comprehensibility of Internet Standards documents
(ISDs) -- i.e., RFCs, Internet-Drafts, and other material produced as
part of the Internet Standards Process [R2026] -- and of all other
Internet-related material, too. A few non-security, networking terms
are included to make the Glossary self-contained, but more complete
glossaries of networking terms are available elsewhere [A1523, F1037,
R1208, R1983].
This Glossary supports the goals of the Internet Standards Process:
o Clear, Concise, Easily Understood Documentation
This Glossary seeks to improve comprehensibility of security-
related content of ISDs. That requires wording to be clear and
understandable, and requires the set of security-related terms and
definitions to be consistent and self-supporting. Also,
terminology needs to be uniform across all ISDs; i.e., the same
term or definition needs to be used whenever and wherever the same
concept is mentioned. Harmonization of existing ISDs need not be
done immediately, but it is desirable to correct and standardize
terminology when new versions are issued in the normal course of
standards development and evolution.
o Technical Excellence
Just as Internet Standard (STD) protocols should operate
effectively, ISDs should use terminology accurately, precisely,
and unambiguously to enable standards to be implemented correctly.
o Prior Implementation and Testing
Just as STD protocols require demonstrated experience and
stability before adoption, ISDs need to use well-established
language. Using terms in their plainest, dictionary sense (when
appropriate) helps to ensure international understanding. ISDs
need to avoid using private, made-up terms in place of generally-
accepted terms from open publications. ISDs need to avoid
substituting new definitions that conflict with established ones.
ISDs need to avoid using "cute" synonyms (e.g., see: Green Book),
because no matter how popular a nickname may be in one community,
it is likely to cause confusion in another.
o Openness, Fairness, and Timeliness
ISDs need to avoid terms that are proprietary or otherwise favor a
particular vendor, or that create a bias toward a particular
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security technology or mechanism over other, competing techniques
that already exist or might be developed in the future. The set of
terminology used across the set of ISDs needs to be flexible and
adaptable as the state of Internet security art evolves.
In support of those goals, this Glossary provides guidance by marking
terms and definitions as being either endorsed or deprecated for use
in ISDs. The key words "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY",
and "OPTIONAL" are intended to be interpreted the same way as in an
Internet Standard (i.e., as specified in RFC 2119). Other glossaries
(e.g., [Raym]) list additional terms that deal with Internet security
but have not been included in this Glossary because they are not
appropriate for ISDs.
This Glossary is not an Internet standard, and its guidance
represents only the recommendations of this author. However, this
Glossary provides reasons for its recommendations -- particularly for
the SHOULD NOTs -- so that readers can judge for themselves whether
to follow the guidance.
2. Format of Entries
Section 4 presents Glossary entries in the following manner:
2.1 Order of Entries
Entries are sorted in lexicographic order, without regard to
capitalization. Numeric digits are treated as preceding alphabetic
characters; special characters are treated as preceding digits;
blanks are treated as preceding all other characters; and a hyphen
or slash between two parts of an entry is treated like a blank.
If an entry has multiple definitions (e.g., "domain"), they are
numbered beginning with "1", and any of those multiple definitions
that are RECOMMENDED for use in ISDs are presented before other
definitions for that entry. If definitions are closely related
(e.g., "threat"), they are denoted by adding letters to a number,
such as "1a" and "1b".
2.2 Capitalization and Abbreviations
Entries that are proper nouns are capitalized (e.g., "Data
Encryption Algorithm"), as are other words derived from proper
nouns (e.g., "Caesar cipher"). All other entries are not
capitalized (e.g., "certification authority"). Each acronym or
other abbreviation that appears in this Glossary, either as an
entry or in a definition or explanation, is defined in this
Glossary, except items of common English usage, such as "e.g.",
"etc.", "i.e.", "vol.", "pp.", and "U.S.".
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2.3 Support for Automated Searching
Each entry is preceded by a dollar sign ($) and a space. This
makes it possible to find the defining entry for an item "X" by
searching for the character string "$ X", without stopping at
entries in which "X" is used in explanations.
2.4 Definition Type and Context
Each entry is preceded by a character -- I, N, O, or D -- enclosed
in parentheses, to indicate the type of definition (as is
explained further in Section 3):
- "I" for a RECOMMENDED term or definition of Internet origin.
- "N" if RECOMMENDED but not of Internet origin.
- "O" for a term or definition that is NOT recommended for use in
ISDs but is something that authors of Internet documents need
to know about.
- "D" for a term or definition that is deprecated and SHOULD NOT
be used in Internet documents.
If a definition is valid only in a specific context (e.g.,
"baggage"), that context is shown immediately following the
definition type and is enclosed by a pair of slash symbols (/). If
the definition is valid only for specific parts of speech, that is
shown in the same way (e.g., "archive).
2.5 Explanatory Notes
Some entries have explanatory text that is introduced by one or
more of the following keywords:
- Deprecated Abbreviation (e.g., "EE", "H field", "W3")
- Deprecated Definition (e.g., "digital certification")
- Deprecated Usage (e.g., "authenticate")
- Deprecated Term (e.g., "certificate authority")
- Pronunciation (e.g., "*-property")
- Derivation (e.g., "discretionary access control")
- Tutorial (e.g., "accreditation")
- Example (e.g., "back door")
- Usage (e.g., "access")
Explanatory text in this Glossary MAY be reused in other ISDs.
However, such text is not intended to authoritatively supersede
text of an ISD in which the Glossary entry is already used.
2.6 Cross-References
Some entries contain a parenthetical remark of the form "(See:
X)", where X is a list one of more related Glossary entries. Some
entries contain a remark of the form "(Compare: X)", where X is a
list of other entries that either are antonyms or differ in some
other manner worth observing.
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2.7 Trademarks
All servicemarks and trademarks that appear in this Glossary are
used in an editorial fashion and to the benefit of the mark owner,
without any intention of infringement.
2.8 The New Punctuation
This Glossary uses the "new" or "logical" punctuation style that
is favored by computer programmers, as described in [Raym]:
Programmers use pairs of quotation marks the same way they use
pairs of parentheses, i.e., as balanced delimiters. For example,
if " Alice sends" is a phrase, and so are "Bill receives" and "Eve
listens", then a programmer would write the following sentence:
"Alice sends", "Bill receives", and "Eve listens".
According to standard American usage, the punctuation in that
sentence is incorrect; the continuation commas and the final
period should go inside the string quotes, like this:
"Alice sends," "Bill receives," and "Eve listens."
However, a programmer would not include a character in a literal
string if the character did not belong there, because that could
cause an error. For example, suppose a sentence in a draft of a
tutorial on the vi editing language looked like this:
Then delete one line from the file by typing "dd".
A book editor following standard usage might change the sentence
to look like this:
Then delete one line from the file by typing "dd."
However, in the vi language, the dot character repeats the last
command accepted. So, if a reader entered "dd.", two lines would
be deleted instead of one.
Similarly, use of standard American punctuation might cause
misunderstanding in entries in this Glossary. Thus, the new
punctuation is used here, and we recommend it for ISDs.
3. Types of Definition
Each entry in this Glossary is marked as type I, N, O, or D:
3.1 Type "I": Recommended Term or Definition with Internet Basis
The marking "I" indicates two things:
- Origin: "I" (as opposed to "N") means either that the Internet
Standards Process or Internet community is authoritative for
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the definition *or* that the term is sufficiently generic that
this Glossary can freely state a definition without
contradicting a non-Internet authority (e.g., "attack").
- Recommendation: "I" (as opposed to "O") means that the term and
definition are RECOMMENDED for use in ISDs. However, some "I"
entries may be accompanied by a "Usage" note that states a
limitation (e.g., "certification"), and ISDs SHOULD NOT use the
defined term outside that limited context.
Many "I" entries are proper nouns (e.g., "Internet Protocol") for
which the definition is intended only to provide basic
information; i.e., the authoritative definition of such terms is
found elsewhere. For a proper noun described as an "Internet
protocol", please refer to the current edition of "Internet
Official Protocol Standards" (STD 1) for the standardization
status of the protocol.
3.2 Type "N": Recommended Term or Definition with Non-Internet Basis
The marking "N" indicates two things:
- Origin: "N" (as opposed to "I") means that the entry has a non-
Internet basis or origin.
- Recommendation: "N" (as opposed to "O") means that the term and
definition are RECOMMENDED for use in ISDs, if they are needed
at all in ISDs. Many of these entries are accompanied by a
label that states a context (e.g., "package") or a note that
states a limitation (e.g., "data integrity"), and ISDs SHOULD
NOT use the defined term outside that context or limit. Some of
the contexts are rarely if ever expected to occur in an ISD
(e.g., see: baggage). In those cases, the listing exists to
make Internet authors aware of the non-Internet usage so that
they can avoid conflicts with non-Internet documents.
3.3 Type "O": Other Terms and Definitions To Be Noted
The marking "O" means that the definition has a non-Internet basis
and SHOULD NOT be used in ISDs *except* in cases where the term is
specifically identified as non-Internet.
For example, an ISD might mention "BCA" (see: brand certification
authority) or "baggage" as an example of some concept; in that
case, the document should specifically say "SET(trademark) BCA" or
"SET(trademark) baggage" and include the definition of the term.
3.4 Type "D": Deprecated Terms and Definitions
If this Glossary recommends that an term or definition SHOULD NOT
be used in ISDs, then the entry is marked as type "D", and a
"Deprecated Term", "Deprecated Definition", or "Deprecated Usage"
explanatory note is provided.
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3.5 Definition Substitutions
Some terms have a definition published by a non-Internet authority
-- government (e.g., "object reuse"), industry (e.g., "Secure Data
Exchange"), national authority (e.g., "Data Encryption Standard"),
or international body (e.g., "data confidentiality") -- that is
suitable for use in ISDs. In those cases, this Glossary marks the
definition "N", recommending its use in Internet documents.
Other such terms have definitions that are inadequate or
inappropriate for ISDs. For example, a definition might be
outdated or too narrow, or it might need clarification by
substituting more careful wording (e.g., "authentication
exchange") or explanations, using other terms that are defined in
this Glossary. In those cases, this Glossary marks the entry "O",
and provides an "I" or "N" entry that precedes, and is intended to
supersede, the "O" entry.
In some cases where this Glossary provides a definition to
supersede an "O" definition, the substitute is intended to subsume
the meaning of the "O" entry and not conflict with it. For the
term "security service", for example, the "O" definition deals
narrowly with only communication services provided by layers in
the OSI model and is inadequate for the full range of ISD usage,
while the new "I" definition provided by this Glossary can be used
in more situations and for more kinds of service. However, the "O"
definition is also listed so that ISD authors will be aware of the
context in which the term is used more narrowly.
When making substitutions, this Glossary attempts to avoid
contradicting any non-Internet authority. Still, terminology
differs between the standards of the American Bar Association,
OSI, SET, the U.S. DoD, and other authorities; and this Glossary
probably is not exactly aligned with any of them.
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4. Definitions
$ *-property
(N) Synonym for "confinement property" in the context of the Bell-
LaPadula model. Pronunciation: star property.
$ 3DES
See: Triple Data Encryption Algorithm.
$ A1 computer system
(O) See: TCSEC.
$ AA
See: attribute authority.
$ ABA Guidelines
(N) "American Bar Association (ABA) Digital Signature Guidelines"
[ABA], a framework of legal principles for using digital
signatures and digital certificates in electronic commerce.
$ Abstract Syntax Notation One (ASN.1)
(N) A standard for describing data objects. [Larm, X680] (See:
CMS.)
Usage: This term is often incorrectly used to refer to BER.
Tutorial: OSIRM defines computer network functionality in layers.
Protocols and data objects at higher layers are abstractly defined
to be implemented using protocols and data objects from lower
layers. A higher layer may define transfers of abstract objects
between computers, and a lower layer may define those transfers
concretely as strings of bits. Syntax is needed to specify data
formats of abstract objects, and encoding rules are needed to
transform abstract objects into bit strings at lower layers. OSI
standards use ASN.1 for those specifications and use various
encoding rules for those transformations. (See: BER.)
In ASN.1, formal names are written without spaces, and separate
words in a name are indicated by capitalizing the first letter of
each word except the first word. For example, the name of a CRL is
"certificateRevocationList".
$ ACC
(I) See: access control center.
$ acceptable risk
(I) A risk that is understood and tolerated by a system's
accreditor, usually because the cost or difficulty of implementing
an effective countermeasure for the associated vulnerability
exceeds the expectation of loss. (See: adequate security, (second
law under) Courtney's laws.)
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$ access
1. (I) The ability and means to communicate with or otherwise
interact with a system to use system resources either to handle
information or to gain knowledge of the information the system
contains. (Compare: handle.)
Usage: The definition is intended to include all types of
communication with a system, including one-way communication in
either direction. In actual practice, however, entities that are
outside a security perimeter and can receive output from the
system but cannot provide input or otherwise directly interact
with the system, might be treated as not having "access" (and,
therefore, be exempt from security policy requirements, such as
the need for a security clearance).
2. (O) /formal model/ "A specific type of interaction between a
subject and an object that results in the flow of information from
one to the other." [NCS04]
$ Access Certificate for Electronic Services (ACES)
(O) A PKI operated by the U.S. Government's General Services
Administration in cooperation with industry partners. (See: CAM.)
$ access control
1. (I) Protection of system resources against unauthorized access.
2. (I) A process by which use of system resources is regulated
according to a security policy and is permitted only by authorized
entities (users, programs, processes, or other systems) according
to that policy. (See: access, access control service, computer
security, discretionary access control, mandatory access control,
role-based access control.)
3. (I) /formal model/ Limitations on interactions between subjects
and objects in an information system.
4. (O) "The prevention of unauthorized use of a resource,
including the prevention of use of a resource in an unauthorized
manner." [I7498 Part 2]
5. (O) /U.S. Government/ A system using physical, electronic, or
human controls to identify or admit personnel with properly
authorized access to a SCIF.
$ access control center (ACC)
(I) A computer that maintains a database (possibly in the form of
an access control matrix) defining the security policy for an
access control service, and that acts as a server for clients
requesting access control decisions.
Tutorial: An ACC is sometimes used in conjunction with a key
center to implement access control in a key distribution system
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for symmetric cryptography. (See: BLACKER, Kerberos.)
$ access control list (ACL)
(I) /information system/ A mechanism that implements access
control for a system resource by enumerating the system entities
that are permitted to access the resource and, either implicitly
or explicitly, the types of access granted to each. (Compare:
access control matrix, access list, access profile, capability.)
$ access control matrix
(I) A rectangular array of cells, with one row per subject and one
column per object. The entry in a cell -- that is, the entry for a
particular subject-object pair -- indicates the access mode that
the subject is permitted to exercise on the object. Each column is
equivalent to an "access control list" for the object; and each
row is equivalent to an "access profile" for the subject.
$ access control service
(I) A security service that protects against a system entity using
a system resource in a way not authorized by the system's security
policy. (See: access control, discretionary access control,
identity-based security policy, mandatory access control, rule-
based security policy.)
Tutorial: This service includes protecting against use of a
resource in an unauthorized manner by an entity (i.e., a
principal) that is authorized to use the resource in some other
manner. (See: insider.) The two basic mechanisms for implementing
this service are ACLs and tickets.
$ access level
(D) Synonym for the hierarchical "classification level" in a
security level. [C4009] (See: security level.)
Deprecated Term: ISDs SHOULD NOT use this term; it mixes concepts
in a potentially misleading way. Access control may be based on
attributes other than classification level.
$ access list
(I) /physical security/ Roster of persons who are authorized to
enter a controlled area. (Compare: access control list.)
$ access mode
(I) A distinct type of data processing operation -- e.g., read,
write, append, or execute -- that a subject can potentially
perform on an object in an information system. [Huff]
$ access policy
(I) A kind of "security policy". (See: access, access control.)
$ access profile
(O) /information system/ A mechanism that implements access
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control for a system entity by enumerating the system resources
that the entity is authorized to access and, either implicitly or
explicitly, the types of access granted to each. (Compare: access
control matrix, access control list, access list, capability.)
Usage: The definition is not widely known; therefore, ISDs that
use this term SHOULD state a definition for it.
$ access right
(I) Synonym for "authorization"; emphasizes the possession of the
authorization by a system entity.
$ accountability
(I) The property of a system or system resource that ensures that
the actions of a system entity may be traced uniquely to that
entity, which can then be held responsible for its actions. [Huff]
(See: audit service.)
Tutorial: Accountability (also known as "individual
accountability") typically involves a system capability to
positively associate the identity of a user with the time, method,
and mode of the user's access to the system. This capability
supports detection and subsequent investigation of security
breaches. Individual persons who are system users are held
accountable for their actions after being notified of the rules of
behavior for using the system and the penalties associated with
violating those rules.
$ accounting
See: COMSEC accounting.
$ accounting legend code (ALC)
(O) /U.S. Government/ Numeric system used to indicate the minimum
accounting controls required for items of COMSEC material within
the CMCS. [C4009] (See: COMSEC accounting.)
$ accreditation
(N) An administrative action by which a designated authority
declares that an information system is approved to operate in a
particular security configuration with a prescribed set of
safeguards. [FP102, SP37] (See: certification.)
Tutorial: An accreditation is usually based on a technical
certification of the system's security mechanisms. To accredit a
system, the approving authority must determine that any residual
risk is an acceptable risk. Although the terms "certification" and
"accreditation" are used more in the U.S. DoD and other government
agencies than in commercial organizations, the concepts apply any
place where managers are required to deal with and accept
responsibility for security risks. For example, the American Bar
Association is developing accreditation criteria for CAs.
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$ accreditation boundary
(O) Synonym for "security perimeter". [C4009]
$ accreditor
(N) A management official who has been designated to have the
formal authority to "accredit" an information system, i.e., to
authorize the operation of, and the processing of sensitive data
in, the system and to accept the residual risk associated with the
system. (See: accreditation, residual risk.)
$ ACES
(O) See: Access Certificate for Electronic Services.
$ ACL
(I) See: access control list.
$ acquirer
1. (O) /SET/ "The financial institution that establishes an
account with a merchant and processes payment card authorizations
and payments." [SET1]
2. (O) /SET/ "The institution (or its agent) that acquires from
the card acceptor the financial data relating to the transaction
and initiates that data into an interchange system." [SET2]
$ activation data
(N) Secret data, other than keys, that is required to access a
cryptographic module.
$ active attack
(I) See: (secondary definition under) attack.
$ active content
(O) "Electronic documents that can carry out or trigger actions
automatically on a computer platform without the intervention of a
user. [This technology enables] mobile code associated with a
document to execute as the document is rendered." [SP28]
$ active wiretapping
(I) A wiretapping attack that attempts to alter data being
communicated or otherwise affect data flow. (See: wiretapping.
Compare: active attack, passive wiretapping.)
$ add-on security
(N) The retrofitting of protection mechanisms, implemented by
hardware or software, in an information system after the system
has become operational. [FP039] (Compare: baked-in security.)
$ adequate security
(O) /U.S. DoD/ "Security commensurate with the risk and magnitude
of harm resulting from the loss, misuse, or unauthorized access to
or modification of information." (See: acceptable risk, residual
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risk.)
$ administrative security
1. (I) Management procedures and constraints to prevent
unauthorized access to a system. (See: (third law under)
Courtney's laws, operational security, procedural security,
security architecture. Compare: technical security.)
Examples: Clear delineation and separation of duties;
configuration control.
Usage: Administrative security is usually understood to consist of
methods and mechanisms that are implemented and executed primarily
by people, rather than by automated systems.
2. (O) "The management constraints, operational procedures,
accountability procedures, and supplemental controls established
to provide an acceptable level of protection for sensitive data."
[FP039]
$ administrator
1. (O) /Common Criteria/ A person that is responsible for
configuring, maintaining, and administering the TOE in a correct
manner for maximum security. (See: administrative security.)
2. (O) /ITSEC/ A person in contact with the TOE, who is
responsible for maintaining its operational capability.
$ Advanced Encryption Standard (AES)
(N) A U.S. Government standard [FP197] (the successor to DES) that
(a) specifies the "the AES algorithm", which is a symmetric block
cipher that is based on Rijndael and uses key sizes of 128, 192,
or 256 bits to operate on a 128-bit block, and (b) states policy
for using that algorithm to protect unclassified, sensitive data.
Tutorial: Rijndael was designed to handle additional block sizes
and key lengths that were not adopted in the AES. Rijndael was
selected by NIST through a public competition that was held to
find a successor to the DEA; the other finalists were MARS, RC6,
Serpent, and Twofish.
$ adversary
1. (I) An entity that attacks a system. (Compare: intruder.)
2. (I) An entity that is a threat to a system.
$ AES
(N) See: Advanced Encryption Standard.
$ Affirm
(O) A formal methodology, language, and integrated set of software
tools developed at the University of Southern California's
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Information Sciences Institute for specifying, coding, and
verifying software to produce correct and reliable programs.
[Cheh]
$ aggregation
(I) A circumstance in which a collection of information items is
required to be classified at a higher security level than any of
the items is classified individually.
$ AH
(I) See: Authentication Header
$ air gap
(I) An interface between two systems at which (a) they are not
connected physically and (b) any logical connection is not
automated (i.e., data is transferred through the interface only
manually, under human control). (See: sneaker net.)
Example: Computer A and computer B are on opposite sides of a
room. To move data from A to B, a person carries a floppy disk
across the room. If A and B operate in different security domains,
than moving data across the air gap may involve an upgrade or
downgrade operation.
$ ALC
(O) See: accounting legend code.
$ algorithm
(I) A finite set of step-by-step instructions for a problem-
solving or computation procedure, especially one that can be
implemented by a computer. (See: cryptographic algorithm.)
$ alias
(I) A name that an entity uses in place of its real name, usually
for the purpose of either anonymity or masquerade.
$ Alice and Bob
(I) The parties that are most often called upon to illustrate the
operation of bipartite security protocols. These and other
dramatis personae are listed by Schneier [Schn].
$ American National Standards Institute (ANSI)
(N) A private, not-for-profit association that administers U.S.
private sector voluntary standards.
Tutorial: ANSI has approximately 1,000 member organizations,
including equipment users, manufacturers, and others. These
include commercial firms, government agencies, and other
institutions and international entities.
ANSI is the sole U.S. representative to the two major non-treaty
international standards organizations, ISO and, via the U.S.
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National Committee (USNC), the International Electrotechnical
Commission (IEC).
ANSI provides a forum for ANSI-accredited standards development
groups. Among those groups, the following are especially relevant
to Internet security:
- International Committee for Information Technology
Standardization (INCITS) (formerly X3): Primary U.S. focus of
standardization in information and communications technologies,
encompassing storage, processing, transfer, display,
management, organization, and retrieval of information.
Example: [A3092].
- Accredited Standards Committee X9: Develops, establishes,
maintains, and promotes standards for the financial services
industry. Example: [A9009].
- Alliance for Telecommunications Industry Solutions (ATIS):
Develops standards, specifications, guidelines, requirements,
technical reports, industry processes, and verification tests
for interoperability and reliability of telecommunications
networks, equipment, and software. Example: [A1523].
$ Anderson report
(O) A 1972 study of computer security that was written by James P.
Anderson for the U.S. Air Force [Ande].
Tutorial: Anderson collaborated with a panel of experts to study
Air Force requirements for multilevel security. The study
recommended research and development that was urgently needed to
provide secure information processing for command and control
systems and support systems. The report introduced the reference
monitor concept and provided development impetus for computer and
network security technology. However, many of the security
problems that the 1972 report called "current" still plague
information systems today.
$ anomaly detection
(I) A intrusion detection method that searches for activity that
is different from the normal behavior of system entities and
system resources. (Compare: misuse detection. See: IDS.)
$ anonymity
(I) The condition of having a name that is unknown or concealed.
(Compare: privacy. See: alias, anonymizer, anonymous credential,
anonymous login, persona certificate.)
Tutorial: An application may require security services that
maintain anonymity of users or other system entities, perhaps to
preserve their privacy or hide them from attack. To hide an
entity's real name, an alias may be used. For example, a financial
institution may assign an account number. Parties to a transaction
can thus remain relatively anonymous, but can also accept the
transaction as legitimate. Real names of the parties cannot be
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easily determined by observers of the transaction, but an
authorized third party may be able to map an alias to a real name,
such as by presenting the institution with a court order. In other
applications, anonymous entities may be completely untraceable.
$ anonymizer
(I) A internetwork service, usually provided via a proxy server,
that provides anonymity and privacy for clients. That is, the
service enables a client to access servers without allowing the
anyone to gather information about which servers the client
accesses and without allowing the accessed servers to gather
information about the client, such as its IP address.
$ anonymous credential
(D) /U.S. Government/ An credential that (a) can be used to
authenticate a person as having a specific attribute or being a
member of a specific group (e.g., military veterans or U.S.
citizens) but (b) does not reveal the individual identity of the
person that presents the credential. [M0404]
Deprecated term: ISDs SHOULD NOT use this term; it mixes concepts
in a potentially misleading way. For example, when the credential
is an X.509 certificate, the term could be misunderstood to mean
that the certificate was signed by a CA that has a persona
certificate. Instead, use "attribute certificate", "organizational
certificate", or "persona" certificate" depending on what is
meant, with additional explanations as needed.
$ anonymous login
(I) An access control feature (actually, an access control
vulnerability) in many Internet hosts that enables users to gain
access to general-purpose or public services and resources of a
host (such as allowing any user to transfer data using File
Transfer Protocol) without having a pre-established, identity-
specific account (i.e., user name and password).
Tutorial: This feature exposes a system to more threats than when
all the users are known, pre-registered entities that are
individually accountable for their actions. A user logs in using a
special, publicly known user name (e.g., "anonymous", "guest", or
"ftp"). To use the public login name, the user is not required to
know a secret password and may not be required to input anything
at all except the name. In other cases, to complete the normal
sequence of steps in a login protocol, the system may require the
user to input a matching, publicly known password (such as
"anonymous") or may ask the user for an e-mail address or some
other arbitrary character string.
$ ANSI
(I) See: American National Standards Institute.
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$ anti-jam
(N) "Measures ensuring that transmitted information can be
received despite deliberate jamming attempts." [C4009] (See:
electronic security, frequency hopping, jam, spread spectrum.)
$ API
(I) See: application programming interface.
$ APOP
(I) See: POP3 APOP.
$ application layer
(I) See: Open Systems Interconnection Reference Model (OSIRM).
$ application program
(I) A computer program that performs a specific function directly
for a user (as opposed to a program that is part of a computer
operating system and exists to perform functions in support of
application programs).
$ archive
1a. (I) /noun/ A collection of data that is stored for a
relatively long period of time for historical and other purposes,
such as to support audit service, availability service, or system
integrity service. (Compare: backup, repository.)
1b. (I) /verb/ To store data in such a way as to create an
archive. (Compare: back up.)
Tutorial: A digital signature may need to be verified many years
after the signing occurs. The CA -- the one that issued the
certificate containing the public key needed to verify that
signature -- may not stay in operation that long. So every CA
needs to provide for long-term storage of the information needed
to verify the signatures of those to whom it issues certificates.
$ ARPANET
(N) Advanced Research Projects Agency (ARPA) Network, a pioneer
packet-switched network that was designed, implemented, operated,
and maintained by BBN from January 1969 until July 1975 under
contract to the U.S. Government; led to the development of today's
Internet; and was decommissioned in June 1990. [B4799, Hafn]
$ ASCII
(I) American Standard Code for Information Interchange, a scheme
that encodes 128 specified characters -- the numbers 0-9, the
letters a-z and A-Z, some basic punctuation symbols, some control
codes that originated with Teletype machines, and a blank space --
into the 7-bit binary numbers. Forms the basis of the character
set representations used in most computers and many Internet
standards. (See: code.)
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$ ASN.1
(I) See: Abstract Syntax Notation One.
$ asset
(I) A system resource that is (a) required to be protected by an
information system's security policy, (b) intended to be protected
by a countermeasure, or (c) required for a system's mission.
$ association
(I) A cooperative relationship between system entities, usually
for the purpose of transferring information between them. (See:
security association.)
$ assurance
See: security assurance.
$ assurance level
(I) A rank on a hierarchical scale of confidence that a TOE
adequately fulfills stated security requirements. (See: assurance,
certificate policy, EAL, TCSEC.)
Example: U.S. Government guidance [M0404] describes four assurance
levels for identity authentication, where each level "describes
the [Government] agency~Os degree of certainty that the user has
presented [a credential] that refers to [the user's] identity." In
that guidance, "assurance is defined as (a) "the degree of
confidence in the vetting process used to establish the identity
of the individual to whom the credential was issued" and (b) "the
degree of confidence that the individual who uses the credential
is the individual to whom the credential was issued." The four
levels are described as follows:
- Level 1: Little or no confidence in the asserted identity.
- Level 2: Some confidence in the asserted identity.
- Level 3: High confidence in the asserted identity.
- Level 4: Very high confidence in the asserted identity.
Standards for determining these levels are provided in a NIST
publication [SP12]. However, as noted there, an assurance level is
"a degree of confidence, not a true measure of how secure the
system actually is. This distinction is necessary because it is
extremely difficult -- and in many cases virtually impossible --
to know exactly how secure a system is."
$ asymmetric cryptography
(I) A modern branch of cryptography (popularly known as "public-
key cryptography") in which the algorithms use a pair of keys (a
public key and a private key) and use a different component of the
pair for each of two counterpart cryptographic operations (e.g.,
encryption and decryption, or signature creation and signature
verification). (See: key pair, symmetric cryptography.)
Tutorial: Asymmetric algorithms have key management advantages
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over equivalently strong symmetric ones. First, one key of the
pair need not be known by anyone but its owner; so it can more
easily be kept secret. Second, although the other key is shared by
all entities that use the algorithm, that key need not be kept
secret from other, non-using entities; thus, the key distribution
part of key management can be done more easily.
Asymmetric cryptography can be used to create algorithms for
encryption, digital signature, and key agreement:
- In an asymmetric encryption algorithm (e.g., see: RSA), when
Alice wants to ensure confidentiality for data she sends to
Bob, she encrypts the data with a public key provided by Bob.
Only Bob has the matching private key that is needed to decrypt
the data. (Compare: seal.)
- In an asymmetric digital signature algorithm (e.g., see: DSA),
when Alice wants to ensure data integrity or provide
authentication for data she sends to Bob, she uses her private
key to sign the data (i.e., create a digital signature based on
the data). To verify the signature, Bob uses the matching
public key that Alice has provided.
- In an asymmetric key agreement algorithm (e.g., see: Diffie-
Hellman), Alice and Bob each send their own public key to the
other party. Then each uses their own private key and the
other's public key to compute the new key value.
$ ATIS
(N) See: (Alliance for Telecommunications Industry Solutions
under) ANSI.
$ attack
1. (I) An intentional act by which an entity attempts to evade
security services and violate the security policy of a system.
That is, an actual assault on system security that derives from an
intelligent threat. (See: penetration, violation, vulnerability.)
2. (I) A method or technique used in an assault (e.g.,
masquerade). (See: distributed attack.)
Tutorial: Attacks can be characterized according to intent:
- An "active attack" attempts to alter system resources or affect
their operation.
- A "passive attack" attempts to learn or make use of information
from the system but does not affect system resources. (E.g.,
see: wiretapping.)
The object of a passive attack might be to obtain data that is
needed for an off-line attack.
- An "off-line attack" is one in which the attacker obtains data
from the target system and then analyzes the data on a
different system of the attacker's own choosing, possibly in
preparation for a second stage of attack on the target.
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Attacks can be characterized according to point of initiation:
- An "inside attack" is one that is initiated by an entity inside
the security perimeter (an "insider"), i.e., an entity that is
authorized to access system resources but uses them in a way
not approved by those who granted the authorization.
- An "outside attack" is initiated from outside the perimeter, by
an unauthorized or illegitimate user of the system (an
"outsider"). In the Internet, potential outside attackers range
from amateur pranksters to organized criminals, international
terrorists, and hostile governments.
The term "attack" relates to some other basic security terms as
shown in the following diagram:
+ - - - - - - - - - - - - + + - - - - + + - - - - - - - - - - -+
| An Attack: | |Counter- | | A System Resource: |
| i.e., A Threat Action | | measure | | Target of the Attack |
| +----------+ | | | | +-----------------+ |
| | Attacker |<==================||<========= | |
| | i.e., | Passive | | | | | Vulnerability | |
| | A Threat |<=================>||<========> | |
| | Agent | or Active | | | | +-------|||-------+ |
| +----------+ Attack | | | | VVV |
| | | | | Threat Consequences |
+ - - - - - - - - - - - - + + - - - - + + - - - - - - - - - - -+
$ attack potential
(I) The perceived likelihood of success should an attack be
launched, expressed in terms of the attacker's capability (i.e.,
expertise and resources) and motivation. (Compare: threat, risk.)
$ attack sensing, warning, and response
(I) A set of security services that cooperate with audit service
to detect and react to indications of threat actions, including
both inside and outside attacks. (See: indicator.)
$ attack tree
(I) A branching, hierarchical data structure that represents a set
of potential approaches to achieving an event in which system
security is penetrated or compromised in a specified way. [Moor]
Tutorial: Attack trees are special cases of fault trees. The
security incident that is the goal of the attack is represented as
the root node of the tree, and the ways that an attacker could
reach that goal are iteratively and incrementally represented as
branches and subnodes of the tree. Each subnode defines a subgoal,
and each subgoal may have its own set of further subgoals, etc.
The final nodes on the paths outward from the root, i.e., the leaf
nodes, represent different ways to initiate an attack. Each node
other than a leaf is either an AND-node or an OR-node. To achieve
the goal represented by an AND-node, the subgoals represented by
all of that node's subnodes must be achieved; and for an OR-node,
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at least one of the subgoals must be achieved. Branches can be
labeled with values representing difficulty, cost, or other attack
attributes, so that alternative attacks can be compared.
$ attribute
1. (N) The information of a particular type concerning an
identifiable system entity or object. An "attribute type" is the
component of an attribute that indicates the class of information
given by the attribute; and an "attribute value" is a particular
instance of the class of information indicated by an attribute
type. (See: attribute certificate.)
$ attribute authority (AA)
1. (I) A CA that issues attribute certificates.
2. (O) "An authority [that] assigns privileges by issuing
attribute certificates." [X509]
Usage: The abbreviation "AA" should not be used in an ISD unless
it is first defined in the ISD.
$ attribute certificate
1. (I) A digital certificate that binds a set of descriptive data
items, other than a public key, either directly to a subject name
or to the identifier of another certificate that is a public-key
certificate.
2. (N) "A data structure, digitally signed by an [a]ttribute
[a]uthority, that binds some attribute values with identification
information about its holder." [X509]
Tutorial: A public-key certificate binds a subject name to a
public key value, along with information needed to perform certain
cryptographic functions. Other attributes of a subject, such as a
security clearance, may be certified in a separate kind of digital
certificate, called an attribute certificate. A subject may have
multiple attribute certificates associated with its name or with
each of its public-key certificates.
An attribute certificate might be issued to a subject in the
following situations:
- Different lifetimes: When the lifetime of an attribute binding
is shorter than that of the related public-key certificate, or
when it is desirable not to need to revoke a subject's public
key just to revoke an attribute.
- Different authorities: When the authority responsible for the
attributes is different than the one that issues the public-key
certificate for the subject. (There is no requirement that an
attribute certificate be issued by the same CA that issued the
associated public-key certificate.)
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$ audit
See: security audit.
$ audit log
(I) Synonym for "security audit trail".
$ audit service
(I) A security service that records information needed to
establish accountability for system events and for the actions of
system entities that cause them. (See: security audit.)
$ audit trail
(I) See: security audit trail.
$ AUTH
(I) See: POP3 AUTH.
$ authentic signature
(I) A signature (especially a digital signature) that can be
trusted because it can be verified. (See: validate vs. verify.)
$ authenticate
(I) Verify (i.e., establish the truth of) an identity claimed by
or for a system entity. (See: authentication, validate vs. verify,
("relationship between data integrity service and authentication
services" under) data integrity service.).)
Deprecated Usage: In general English usage, this term is used with
the meaning "to prove genuine" (e.g., an art expert authenticates
a Michelangelo painting); but this Internet definition restricts
usage as follows:
- ISDs SHOULD NOT use this term to refer to proving or checking
that data has not been changed, destroyed or lost in an
unauthorized or accidental manner. Instead use "verify".
- ISDs SHOULD NOT use this term to refer to proving the truth or
accuracy of a fact or value such as a digital signature.
Instead, use "verify".
- ISDs SHOULD NOT use this term to refer to establishing the
soundness or correctness of a construct, such as a digital
certificate. Instead, use "validate".
$ authentication
(I) The process of verifying an identity claimed by or for a
system entity. (See: authenticate, authentication exchange,
authentication information, credential, data origin
authentication, peer entity authentication, simple authentication,
strong authentication, X.509. Also see: ("relationship between
data integrity service and authentication services" under) data
integrity service.)
Tutorial: An authentication process consists of two steps:
- Identification step: Presenting an identifier to the security
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system. (Identifiers should be assigned carefully, because
authenticated identities are the basis for other security
services, such as access control service.)
- Verification step: Presenting or generating authentication
information that acts as evidence to prove the binding between
the claimant and the identifier. (See: verification.)
$ authentication code
(D) Synonym for a checksum based on cryptography. (Compare:
Message Authentication Code.)
Deprecated Term: ISDs SHOULD NOT use this term as a synonym for
any form of checksum, cryptographic or not; the term mixes
concepts in a potentially misleading way. Instead, use "checksum",
"error detection code", "hash", "keyed hash", "Message
Authentication Code", or "protected checksum", depending on what
is meant.
The word "authentication" is misleading because the checksum may
be used to perform a data integrity function rather than a data
origin authentication function. The word "code" is misleading
because it suggests either that encoding or encryption is involved
or that the term refers to computer software.
$ authentication exchange
1. (I) A mechanism to verify the identity of an entity by means of
information exchange.
2. (O) "A mechanism intended to ensure the identity of an entity
by means of information exchange." [I7498 Part 2]
$ Authentication Header (AH)
(I) An Internet protocol [R2402] designed to provide
connectionless data integrity service and connectionless data
origin authentication service for IP datagrams, and (optionally)
to provide partial sequence integrity and protection against
replay attacks. (See: IPsec. Compare: ESP.)
Tutorial: Replay protection may be selected by the receiver when a
security association is established. AH authenticates upper-layer
protocol data units and as much of the IP header as possible.
However, some IP header fields may change in transit, and the
value of these fields, when the packet arrives at the receiver,
may not be predictable by the sender. Thus, the values of such
fields cannot be protected end-to-end by AH; protection of the IP
header by AH is only partial when such fields are present.
AH may be used alone, or in combination with the ESP, or in a
nested fashion with tunneling. Security services can be provided
between a pair of communicating hosts, between a pair of
communicating security gateways, or between a host and a gateway.
ESP can provide nearly the same security services as AH, and ESP
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can also provide data confidentiality service. The main difference
between authentication services provided by ESP and AH is the
extent of the coverage; ESP does not protect IP header fields
unless they are encapsulated by AH.
$ authentication information
(I) Information used to verify an identity claimed by or for an
entity. (See: authentication, credential, user. Compare:
identification information.)
Tutorial: Authentication information may exist as, or be derived
from, one of the following: (a) Something the entity knows (see:
password); (b) something the entity possesses (see: token); (c)
something the entity is (see: biometric authentication).
$ authentication service
(I) A security service that verifies an identity claimed by or for
an entity. (See: authentication.)
Tutorial: In a network, there are two general forms of
authentication service: data origin authentication service and
peer entity authentication service.
$ authenticity
(I) The property of being genuine and able to be verified and be
trusted. (See: authenticate, authentication, validate vs. verify.)
$ authority
(D) "An entity, responsible for the issuance of certificates."
[X509]
Deprecated Term: ISDs SHOULD NOT use this term as a synonym for
attribute authority, certification authority, registration
authority, or similar terms; the shortened form may cause
confusion. Instead, use the full term at the first instance of
usage and then, if it is necessary to shorten text, use AA, CA,
RA, and other abbreviations defined in this Glossary.
$ authority certificate
(D) "A certificate issued to an authority (e.g. either to a
certification authority or to an attribute authority)." [X509]
(See: authority.)
Deprecated Term: ISDs SHOULD NOT use this term as defined here; it
is ambiguous. Instead, use the full term "certification authority
certificate", "attribute authority certificate", "registration
authority certificate", etc. at the first instance of usage and
then, if it is necessary to shorten text, use AA, CA, RA, and
other abbreviations defined in this Glossary.
$ authorization
1a. (I) An approval that is granted to a system entity to access a
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system resource. (Compare: permission, privilege.)
Usage: Some synonyms are "permission" and "privilege". Specific
terms are preferred in certain contexts:
- /PKI/ "Authorization" SHOULD be used, to align with
"certification authority" in the standard [X509].
- /role-based access control/ "Permission" SHOULD be used, to
align with the standard [ANSI].
- /computer operating systems/ "Privilege" SHOULD be used, to
align with the literature.
Tutorial: The semantics and granularity of authorizations depend
on the application and implementation (see: (first law under)
Courtney's laws). An authorization may specify a particular access
mode -- such as read, write, or execute -- for one or more system
resources.
1b. (I) A process for granting approval to a system entity to
access a system resource.
2. (O) /SET/ "The process by which a properly appointed person or
persons grants permission to perform some action on behalf of an
organization. This process assesses transaction risk, confirms
that a given transaction does not raise the account holder's debt
above the account's credit limit, and reserves the specified
amount of credit. (When a merchant obtains authorization, payment
for the authorized amount is guaranteed -- provided, of course,
that the merchant followed the rules associated with the
authorization process.)" [SET2]
$ authorization credential
(I) See: ("access control" context under) "credential".
$ authorize
(I) Grant an authorization to a system entity.
$ authorized user
(I) /access control/ A system entity that accesses a system
resource for which the entity has received an authorization.
(Compare: insider, outsider, unauthorized user.)
Usage: The term is used in many ways and could easily be
misunderstood; ISD that use this term SHOULD state a definition
for it.
$ automated information system
See: information system.
$ availability
1. (I) The property of a system or a system resource being
accessible, or usable or operational upon demand, by an authorized
system entity, according to performance specifications for the
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system; i.e., a system is available if it provides services
according to the system design whenever users request them. (See:
critical, denial of service. Compare: precedence, reliability,
survivability.)
2. (O) "The property of being accessible and usable upon demand by
an authorized entity." [I7498 Part 2]
$ availability service
(I) A security service that protects a system to ensure its
availability.
Tutorial: This service addresses the security concerns raised by
denial-of-service attacks. It depends on proper management and
control of system resources, and thus depends on access control
service and other security services.
$ B1 computer system, B2 computer system, B3 computer system
(O) See: TCSEC.
$ back door
1. (I) /computer security/ A computer system feature -- which may
be (a) an unintentional flaw, (b) a mechanism deliberately
installed by the system's creator, or (c) a mechanism
surreptitiously installed by an intruder -- that provides access
to a system resource by other than the usual procedure and usually
is hidden or otherwise not well-known. (Compare: Trojan Horse.
See: maintenance hook.)
Example: A way to access a computer other than through a normal
login. Such an access path is not necessarily designed with
malicious intent; operating systems sometimes are shipped by the
manufacturer with hidden accounts intended for use by field
service technicians or the vendor's maintenance programmers.
2. (I) /cryptography/ A feature of a cryptographic system that
makes it easily possible to break or circumvent the protection
that the system is designed to provided.
Example: A feature that makes it possible to decrypt cipher text
much more quickly than by brute force cryptanalysis, without
having prior knowledge of the decryption key.
$ back up
(I) /verb/ Create a reserve copy of data (compare: archive) or,
more generally, provide alternate means to perform system
functions despite loss of system resources. (See: contingency
plan.)
$ backup
(I) /noun or adjective/ Refers to alternate means of performing
system functions despite loss of system resources. (See:
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contingency plan).
Example: A reserve copy of data, preferably one that is stored
separately from the original, for use if the original becomes lost
or damaged. (Compare: archive.)
$ baggage
(O) /SET/ An "opaque encrypted tuple, which is included in a SET
message but appended as external data to the PKCS encapsulated
data. This avoids superencryption of the previously encrypted
tuple, but guarantees linkage with the PKCS portion of the
message." [SET2]
Deprecated Usage: ISDs SHOULD NOT use this term to describe a data
element, except in the form "SET(trademark) baggage" with the
meaning given above.
$ baked-in security
(I) The inclusion of security mechanisms in an information system
beginning at an early point in the system's life cycle, i.e.,
during the design phase, or at least early in the implementation
phase. (Compare: add-on security.)
Deprecated Term: It is likely that other cultures have different
metaphors for this concept. Therefore, to ensure international
understanding, ISDs SHOULD NOT use this term. (See: (Deprecated
Usage under) Green Book.)
$ bandwidth
(I) The total width of the frequency band that is available to or
used by a communication channel; usually expressed in Hertz (Hz).
[R3753] (Compare: channel capacity.)
$ bank identification number (BIN)
1. (O) The digits of a credit card number that identify the
issuing bank. (See: primary account number.)
2. (O) /SET/ The first six digits of a primary account number.
$ Basic Encoding Rules (BER)
(I) A standard for representing ASN.1 data types as strings of
octets. [X690] (See: Distinguished Encoding Rules.)
Usage: Sometimes incorrectly included under the term ASN.1, which
properly refers only to the syntax description language, and not
to the encoding rules for the language.
$ Basic Security Option
(I) See: (secondary definition under) IPSO.
$ bastion host
(I) A strongly protected computer that is in a network protected
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by a firewall (or is part of a firewall) and is the only host (or
one of only a few) in the network that can be directly accessed
from networks on the other side of the firewall. (See: firewall.)
Tutorial: Filtering routers in a firewall typically restrict
traffic from the outside network to reaching just one host, the
bastion host, which usually is part of the firewall. Since only
this one host can be directly attacked, only this one host needs
to be very strongly protected, so security can be maintained more
easily and less expensively. However, to allow legitimate internal
and external users to access application resources through the
firewall, higher layer protocols and services need to be relayed
and forwarded by the bastion host. Some services (e.g., DNS and
SMTP) have forwarding built in; other services (e.g., TELNET and
FTP) require a proxy server on the bastion host.
$ BBN Technologies
(O) The research-and-development company (originally called Bolt
Baranek and Newman, Inc.) that built the ARPANET.
$ BCA
(O) See: brand certification authority.
$ BCR (black/crypto/red)
(N) An experimental, end-to-end, network packet encryption system
developed in a working prototype form by BBN and the Collins Radio
division of Rockwell Corporation in the 1975-1980 time frame for
the U.S. DoD. BCR was the first network security system to support
TCP/IP traffic, and it incorporated the first DES chips that were
validated by the U.S. National Bureau of Standards (now called
NIST). BCR also was the first to use a KDC and an ACC to manage
connections.
$ BCI
(O) See: brand CRL identifier.
$ Bell-LaPadula model
(N) A formal, mathematical, state-transition model of
confidentiality policy for multilevel-secure computer systems
[Bell]. (Compare: Biba model, Brewer-Nash model.)
Tutorial: The model, devised by David Bell and Leonard LaPadula at
The MITRE Corporation in 1973, characterizes computer system
elements as subjects and objects. To determine whether or not a
subject is authorized for a particular access mode on an object,
the clearance of the subject is compared to the classification of
the object. The model defines the notion of a "secure state", in
which the only permitted access modes of subjects to objects are
in accordance with a specified security policy. It is proven that
each state transition preserves security by moving from secure
state to secure state, thereby proving that the system is secure.
In this model, a multilevel-secure system satisfies several rules,
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including the "confinement property" (also called "*-property",
pronounced "star property"), the "simple security property", and
the "tranquillity property".
$ benign
(N) "Condition of cryptographic data [such] that [it] cannot be
compromised by human access [to the data]." [C4009]
$ benign fill
(N) Process by which keying material is generated, distributed,
and placed into an ECU without exposure to any human or other
system entity, except the cryptographic module that consumes and
uses the material.
$ BER
(I) See: Basic Encoding Rules.
$ beyond A1
1. (O) /formal/ A level of security assurance that is beyond the
highest level (level A1) of criteria specified by the TCSEC.
2. (O) /informal/ A level of trust so high that it is beyond
state-of-the-art technology; i.e., it cannot be provided or
verified by currently available assurance methods, and especially
not by currently available formal methods.
$ Biba model
(N) A formal, mathematical, state-transition model of integrity
policy for multilevel-secure computer systems [Biba]. (Compare:
Bell-LaPadula model.)
Tutorial: This model for integrity control is analogous to the
Bell-LaPadula model for confidentiality control. Each subject and
object is assigned an integrity level and, to determine whether or
not a subject is authorized for a particular access mode on an
object, the integrity level of the subject is compared to that of
the object. The model prohibits the changing of information in an
object by a subject with a lesser or incomparable level. The rules
of the Biba model are duals of the corresponding rules in the
Bell-LaPadula model.
$ billet
(N) A position or assignment that can be filled by one system
entity at a time. [JCSP1] (Compare: principal, role, user.)
Tutorial: In an organization, a "billet" is a populational
position, of which there is exactly one instance; but a "role" is
functional position, of which there can be multiple instances.
System entities are in one-to-one relationships with their
billets, but may be in many-to-one and one-to-many relationships
with their roles.
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$ BIN
(O) See: bank identification number.
$ bind
(I) To inseparably associate by applying some mechanism.
Example: A CA uses a digital signature to bind together (a) a
subject and (b) a public key, and possibly some additional,
secondary data items, to create a public-key certificate.
$ biometric authentication
(I) A method of generating authentication information for a person
by digitizing measurements of a physical or behavioral
characteristic, such as a fingerprint, hand shape, retina pattern,
voiceprint, handwriting style, or face.
$ birthday attack
(I) A class of attacks against cryptographic functions, including
both encryption functions and hash functions. The attacks take
advantage of a statistical property: Given a cryptographic
function having an N-bit output, the probability is greater than
1/2 that for 2**(N/2) randomly chosen inputs, the function will
produce at least two outputs that are identical. (See: (discussion
under) hash function.)
Derivation: From the somewhat surprising fact (often called the
"birthday paradox") that although there are 365 days in a year,
the probability is greater than 1/2 that two of more people share
the same birthday in any randomly chosen group of 23 people.
$ bit
(I) A contraction of the term "binary digit", the smallest unit of
information storage, which has two possible states or values that
are usually represented by the symbols "0" (zero) and "1" (one).
(See: block, byte, word.)
$ bit string
(I) A sequence of bits, each of which is either "0" or "1".
$ BLACK
1. (I) Designation for data that consists only of cipher text, and
for information system equipment items or facilities that handle
only cipher text. Example: "BLACK key".(Compare: RED. See: color
change, RED/BLACK separation.)
2. (O) /U.S. Government/ "Designation applied to information
systems, and to associated areas, circuits, components, and
equipment, in which national security information is encrypted or
is not processed. [C4009]
$ BLACK key
(I) A key that is protected with a key-encrypting key and that
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must be decrypted before use. (Compare: RED key. See: BLACK.)
$ BLACKER
(N) An end-to-end encryption system for computer data networks
that was developed by the U.S. DoD in the 1980s to provide host-
to-host data confidentiality service for datagrams at OSIRM layer
3. [Weis] (Compare: Caneware, IPsec.)
Tutorial: Each user host connects to its own bump-in-the-wire
encryption device called a BLACKER Front End (BFE, TSEC/KI-111),
through which the host connects to the subnetwork. The system also
includes two types of centralized devices: one or more KDCs
connect to the subnetwork and communicate with assigned sets of
BFEs, and one or more ACCs connect to the subnetwork and
communicate with assigned KDCs. BLACKER uses only symmetric
encryption. A KDC distributes session keys to BFE pairs as
authorized by an ACC. Each ACC maintains a database for a set of
BFEs, and the database determines which pairs from that set (i.e.,
which pairs of user hosts behind the BFEs) are authorized to
communicate and at what security levels.
The BLACKER system is MLS in three ways: (a) The BFEs form a
security perimeter around a subnetwork, separating user hosts from
the subnetwork, so that the subnetwork can operate at a different
security level (possibly a lower, less expensive level) than the
hosts. (b) The BLACKER components are trusted to separate
datagrams of different security levels, so that each datagram of a
given security level can be received only by a host that is
authorized for that security level; and thus BLACKER can separate
host communities that operate at different security levels. (c)
The host side of a BFE is itself MLS and can recognize a security
label on each packet, so that an MLS user host can be authorized
to successively transmit datagrams that are labeled with different
security levels.
$ block
(I) A bit string or bit vector of finite length. (See: block
cipher. Compare: byte, word.)
Usage: An "N-bit block" contains N bits, which usually are
numbered from left to right as 1, 2, 3, ..., N.
$ block cipher
(I) An encryption algorithm that breaks plain text into fixed-size
segments and uses the same key to transform each plaintext segment
into a fixed-size segment of cipher text. Examples: Blowfish, DEA,
IDEA, RC2, and SKIPJACK. (See: block, mode. Compare: stream
cipher.)
Tutorial: A block cipher can be adapted to have a different
external interface, such as that of a stream cipher, by using a
mode of operation to "package" the basic algorithm.
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$ Blowfish
(N) A symmetric block cipher with variable-length key (32 to 448
bits) designed in 1993 by Bruce Schneier as an unpatented,
license-free, royalty-free replacement for DES or IDEA. [Schn]
$ brand
1. (I) A distinctive mark or name that identifies a product or
business entity.
2. (O) /SET/ The name of a payment card.
Tutorial: Financial institutions and other companies have founded
payment card brands, protect and advertise the brands, establish
and enforce rules for use and acceptance of their payment cards,
and provide networks to interconnect the financial institutions.
These brands combine the roles of issuer and acquirer in
interactions with cardholders and merchants. [SET1]
$ brand certification authority (BCA)
(O) /SET/ A CA owned by a payment card brand, such as MasterCard,
Visa, or American Express. [SET2] (See: certification hierarchy,
SET.)
$ brand CRL identifier (BCI)
(O) /SET/ A digitally signed list, issued by a BCA, of the names
of CAs for which CRLs need to be processed when verifying
signatures in SET messages. [SET2]
$ break
(I) /cryptography/ To successfully perform cryptanalysis and thus
succeed in decrypting data or performing some other cryptographic
function, without initially having knowledge of the key that the
function requires. (See: penetrate.)
Usage: This term applies to encrypted data or, more generally, to
a cryptographic algorithm or cryptographic system.
$ Brewer-Nash model
(N) A security model [BN89] to enforce the Chinese wall policy.
(Compare: Bell-LaPadula model, Clark-Wilson model.)
Tutorial: All proprietary information in the set of commercial
firms F(1), F(2), ..., F(N) is categorized into mutually exclusive
conflict-of-interest classes I(1), I(2), ..., I(M) that apply
across all firms. Each firm belongs to exactly one class. The
Brewer-Nash model has the following mandatory rules:
- Brewer-Nash Read Rule: Subject S can read information object O
from firm F(i) only if either (a) O is from the same firm as
some object previously read by S *or* (b) O belongs to a class
I(i) from which S has not previously read any object. (See:
object, subject.)
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- Brewer-Nash Write Rule: Subject S can write information object
O to firm F(i) only if (a) S can read O by the Brewer-Nash Read
Rule *and* (b) no object can be read by S from a different firm
F(j), no matter whether F(j) belongs to the same class as F(i)
or to a different class.
$ bridge
(I) A gateway for traffic flowing at OSIRM layer 2 between two
networks (usually two LANs). (Compare: router, bridge CA.)
$ bridge CA
(I) A PKI consisting of only a CA that cross-certifies with CAs of
some other PKIs. (See: cross-certification. Compare: bridge.)
Tutorial: A bridge CA functions as a hub that enables a
certificate user in any of the PKIs that attach to the bridge, to
validate certficates issued in the other attached PKIs.
For example, a bridge CA (BCA) CA1
could cross-certify with four ^
PKIs that have the roots CA1, |
CA2, CA3, and CA4. The cross- v
certificates that the roots CA2 <-> BCA <-> CA3
exchange with the BCA enable an ^
end entity EE1 certified under |
under CA1 in PK1 to construct v
a certification path needed to CA4
validate the certificate of
end entity EE2 under CA2, CA1 -> BCA -> CA2 -> EE2
or vice versa. CA2 -> BCA -> CA1 -> EE1
$ British Standard 7799
(N) Part 1 of the standard is a code of practice for how to secure
an information system. Part 2 specifies the management framework,
objectives, and control requirements for information security
management systems. [BS7799] (See: ISO 17799.)
$ browser
(I) An client computer program that can retrieve and display
information from servers on the World Wide Web. Examples:
Netscape's Navigator and Microsoft's Internet Explorer.
$ brute force
(I) A cryptanalysis technique or other kind of attack method
involving an exhaustive procedure that tries a large number of
possible solutions to the problem, one-by-one.
Tutorial: In some cases, brute force involves trying all of the
possibilities. For example, for cipher text where the analyst
already knows the decryption algorithm, a brute force technique
for finding matching plain text is to decrypt the message with
every possible key. In other cases, brute force involves trying a
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large number of possibilities but substantially fewer than all of
them. For example, given a hash function that produces a N-bit
hash result, the probability is greater than 1/2 that the analyst
will find two inputs that have the same hash result after trying
only 2**(N/2) random chosen inputs. (See: birthday attack.)
$ BS7799
(N) See: British Standard 7799.
$ buffer overflow
(I) Any attack technique that exploits a vulnerability resulting
from computer software or hardware that does not check for
exceeding the bounds of a storage area when data is written into a
sequence of storage locations beginning in that area.
Tutorial: By causing a normal system operation to write data
beyond the bounds of a storage area, the attacker seeks to either
disrupt system operation or cause the system to execute malicious
software inserted by the attacker.
$ buffer zone
(I) A neutral internetwork segment used to connect other segments
that each operate under a different security policy.
Tutorial: To connect a private network to the Internet or some
other relatively public network, one could construct a small,
separate, isolated LAN and connect it to both the private network
and the public network; one or both of the connections would
implement a firewall to limit the traffic that could pass through
the buffer zone.
$ bulk encryption
(N) "Simultaneous encryption of all channels of a multichannel
telecommunications link." [C4009] (Compare: bulk keying material.)
$ bulk key
(D) In a few published descriptions of hybrid encryption for SSH,
Windows 2000, and other applications, this term refers to a
symmetric key that (a) is used to encrypt a relatively large
amount of data and (b) is itself encrypted with a public key.
Example: To send a large file to Bob, Alice (a) generates a
symmetric key and uses it to encrypt the file (i.e., encrypt the
bulk of the information that is to be sent) and then (b) encrypts
that symmetric key (the "bulk key") with Bob's public key.
Deprecated Term: ISDs SHOULD NOT use this term or definition; they
are not well-established and could be confused with the
established term "bulk keying material". Instead, use "symmetric
key" and carefully explain how the key is applied.
$ bulk keying material
(O) Refers to handling keying material in large quantities, e.g.,
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as a dataset that contains many items of keying material. (See:
type 0. Compare: bulk key, bulk encryption.)
$ bump-in-the-stack
(I) An implementation approach that places a network security
mechanism inside the system that is to be protected. (Compare:
bump-in-the-wire.)
Example: IPsec can be implemented inboard, in the protocol stack
of an existing system or existing system design, by placing a new
layer placed between the existing IP layer and the OSIRM layer 3
drivers. Source code access for the existing stack is not
required, but the system that contains the stack does need to be
modified [R1401].
$ bump-in-the-wire
(I) An implementation approach that places a network security
mechanism outside of the system that is to be protected. (Compare:
bump-in-the-stack.)
Example: IPsec can be implemented outboard, in a physically
separate device, so that the system that receives the IPsec
protection does not need to be modified at all [R1401]. Military-
grade link encryption has mainly been implemented as bump-in-the-
wire devices.
$ byte
(I) A fundamental unit of computer storage; the smallest
addressable unit in a computer's architecture. Usually holds one
character of information and, today, usually means eight bits.
(Compare: octet.)
Usage: Understood to be larger than a "bit", but smaller than a
"word". Although "byte" almost always means "octet" today, some
computer architectures have had bytes in other sizes (e.g., six
bits, nine bits). Therefore, an STD SHOULD state the number of
bits in a byte where the term is first used in the STD.
$ C field
(D) See: Compartments field.
$ C1 computer system, C2 computer system
(O) See: TCSEC.
$ CA
(I) See: certification authority.
$ CA certificate
(D) "A [digital] certificate for one CA issued by another CA."
[X509]
Deprecated Definition: An ISD that uses the term SHOULD state
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precisely how the certificate is constructed and how it is
intended to be used; the X.509 definition is ambiguous with regard
to those details. (See: certificate profile.)
- Constraints: A v3 X.509 public-key certificate may have a
"basicConstraints" extension containing a "cA" value of "TRUE"
that specifically indicates that "the certified public key may
be used to verify certificate signatures."
- Key Usage: A v3 X.509 public-key certificate also may have a
"key Usage" extension which indicates the purposes for which
the public key may be used. One purpose is "keyCertSign", for
verifying a CA's signature on certificates; and if this value
is present, than "cA" is also set to "TRUE" if the certificate
also has a "basicConstraints" extension.
However, a CA could be issued a certificate in which "keyCertSign"
is asserted without "basicConstraints" being present; and an
entity that acts as a CA could be issued a certificate with
"keyUsage" set to other values, either with or without
"keyCertSign".
$ Caesar cipher
(I) A cipher that, given an alphabet of N characters, A(1), A(2),
character A(i) by A(i+K, mod N) for some 0<K<N+1. [Schn]
Examples: During the Gallic wars, Julius Caesar used a cipher with
K=3. In a Caesar cipher with K=3 for the English alphabet, A is
replaced by D, B by E, C by F, ..., W by Z, X by A, Y by B, Z by
C.
UNIX systems sometimes include ROT13 software that implements a
Caesar cipher with K=13 (i.e., ROTate by 13).
$ call back
(I) An authentication technique for terminals that remotely access
a computer via telephone lines; the host system disconnects the
caller and then reconnects on a telephone number that was
previously authorized for that terminal.
$ CAM
(O) See: Certificate Arbitrator Module.
$ CANEWARE
(N) A end-to-end encryption system for computer data networks that
was developed by the U.S. DoD in the 1980s to provide host-to-host
data confidentiality service for datagrams in OSIRM layer 3.
[Roge] (Compare: BLACKER, IPsec.)
Tutorial: Each user host connects to its own bump-in-the-wire
encryption device called a CANEWARE Front End (CFE), through which
the host connects to the subnetwork. CANEWARE uses symmetric
encryption for CFE-to-CFE traffic, but also uses FIREFLY to
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establish those session keys. The public-key certificates issued
by the FIREFLY system include credentials for mandatory access
control. For discretionary access control, the system also
includes one or more centralized CANEWARE Control Processors
(CCPs) that connect to the subnetwork, maintain a database for
discretionary access control authorizations, and communicate those
authorizations to assigned sets of CFEs.
The CANEWARE system is MLS in only two of the three ways that
BLACKER is MLS: (a) Like BLACKER BFEs, CFEs form a security
perimeter around a subnetwork, separating user hosts from the
subnetwork, so that the subnetwork can operate at a different
security level than the hosts. (b) Like BLACKER, the CANEWARE
components are trusted to separate datagrams of different security
levels, so that each datagram of a given security level can be
received only by a host that is authorized for that security
level; and thus CANEWARE can separate host communities that
operate at different security levels. (c) Unlike a BFE, the host
side of a CFE is not MLS, and treats all packets received from a
user host as being at the same mandatory security level.
$ capability
(I) A token, usually an unforgeable data object, that gives the
bearer or holder the right to access a system resource. Possession
of the token is accepted by a system as proof that the holder has
been authorized to access the resource indicated by the token.
(Compare: access control list. See: attribute certificate,
credential, digital certificate, ticket.)
$ Capability Maturity Model (CMM)
(N) Method for judging the maturity of software processes in an
organization and for identifying crucial practices needed to
increase process maturity. [Chris] (Compare: Common Criteria.)
Tutorial: The CMM does not specify security evaluation criteria
(see: assurance level), but its use may improve security
assurance. The CMM describes principles and practices that can
improve software processes in terms of evolving from ad hoc
processes to disciplined processes. The CMM has five levels:
- Initial: Software processes are ad hoc or chaotic, and few are
well-defined. Success depends on individual effort and heroics.
- Repeatable: Basic project management processes are established
to track cost, schedule, and functionality. Necessary process
discipline is in place to repeat earlier successes on projects
with similar applications.
- Defined: Software process for both management and engineering
activities is documented, standardized, and integrated into a
standard software process for the organization. All projects
use approved, tailored version of organization's standard
software process for developing and maintaining software.
- Managed: Detailed measures of software process and product
quality are collected. Both software process and products are
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quantitatively understood and controlled.
- Optimizing: Continuous process improvement is enabled by
quantitative feedback from the process and from piloting
innovative ideas and technologies.
$ CAPI
(I) See: cryptographic application programming interface.
$ CAPSTONE
(N) An integrated microcircuit (in MYK-8x series manufactured by
Mykotronx, Inc.) that implements SKIPJACK, KEA, DSA, SHA, and
basic mathematical functions needed to support asymmetric
cryptography; has non-deterministic random number generator; and
supports key escrow. (See: FORTEZZA. Compare: CLIPPER.)
$ card
See: cryptographic card, FORTEZZA, payment card, PC card, smart
card, token.
$ card backup
See: token backup.
$ card copy
See: token copy.
$ card restore
See: token restore.
$ cardholder
1. (I) An entity to whom or to which a card has been issued.
Usage: Usually refers to a living human being, but may refer to a
position (see: billet, role) in an organization or to an automated
process. (See: user.)
2. (O) /SET/ "The holder of a valid payment card account and user
of software supporting electronic commerce." [SET2] A cardholder
is issued a payment card by an issuer. SET ensures that in the
cardholder's interactions with merchants, the payment card account
information remains confidential. [SET1]
$ cardholder certificate
(O) /SET/ A digital certificate that is issued to a cardholder
upon approval of the cardholder's issuing financial institution
and that is transmitted to merchants with purchase requests and
encrypted payment instructions, carrying assurance that the
account number has been validated by the issuing financial
institution and cannot be altered by a third party. [SET1]
$ cardholder certification authority (CCA)
(O) /SET/ A CA responsible for issuing digital certificates to
cardholders and operated on behalf of a payment card brand, an
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issuer, or another party according to brand rules. A CCA maintains
relationships with card issuers to allow for the verification of
cardholder accounts. A CCA does not issue a CRL but does
distribute CRLs issued by root CAs, brand CAs, geopolitical CAs,
and payment gateway CAs. [SET2]
$ CAST
(N) A design procedure for symmetric encryption algorithms, and a
resulting family of algorithms, invented by Carlisle Adams (C.A.)
and Stafford Tavares (S.T.). [R2144, R2612]
$ category
(I) A grouping of sensitive information items to which a non-
hierarchical restrictive security label is applied to increase
protection of the data. (See: compartment. Compare:
classification.)
$ CAW
(O) See: certification authority workstation.
$ CBC
(N) See: cipher block chaining.
$ CCA
(O) See: cardholder certification authority.
$ CCEP
(O) See: Commercial COMSEC Endorsement Program.
$ CCI
(O) See: Controlled Cryptographic Item.
$ CCITT
(N) Acronym for French translation of International Telephone and
Telegraph Consultative Committee. Now renamed ITU-T.
$ CERIAS
(O) Purdue University's Center for Education and Research in
Information Assurance and Security, which includes faculty from
multiple schools and departments and takes multidisciplinary
approach to security problems ranging from technical to ethical,
legal, educational, communicational, linguistic, and economic.
$ CERT
(I) See: computer emergency response team.
$ certificate
1. (I) /general English/ A document that attests to the truth of
something or the ownership of something.
2. (I) /general security/ See: capability, digital certificate.
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3. (I) /PKI/ See: attribute certificate, public-key certificate.
$ Certificate Arbitrator Module (CAM)
(O) An open-source software module that is designed to be
integrated with an application for the purpose of routing,
replying to, and otherwise managing and meditating certificate
validation requests between that application and the CAs in the
ACES PKI.
$ certificate authority
(D) Synonym for "certification authority".
Deprecated Term: ISDs SHOULD NOT use this term; it looks like
sloppy use of "certification authority", which is the term
standardized by X.509. A person who uses this term probably has
not read the PKI standards [X509, R2459].
$ certificate chain
(D) Synonym for "certification path". (See: trust chain.)
Deprecated Term: ISDs SHOULD NOT use this term; it duplicates the
meaning of a standardized term. Instead, use "certification path".
$ certificate chain validation
(D) Synonym for "certificate validation" or "path validation".
Deprecated Term: ISDs SHOULD NOT use this term; it duplicates the
meaning of standardized terms and mixes concepts in a potentially
misleading way. Instead, use "certificate validation" or "path
validation", depending on what is meant. (See: validate vs.
verify.)
$ certificate creation
(I) The act or process by which a CA sets the values of a digital
certificate's data fields and signs it. (See: issue.)
$ certificate expiration
(I) The event that occurs when a certificate ceases to be valid
because its assigned lifetime has been exceeded. (See: certificate
revocation, validity period.)
$ certificate extension
(I) See: extension.
$ certificate holder
(D) Synonym for "certificate subject". (See: certificate owner.)
Deprecated Term: ISDs SHOULD NOT use this term as a synonym for
the subject of a digital certificate; the term is potentially
ambiguous. For example, the term could refer to a system entity or
component, such as a repository, that simply has possession of a
copy of the certificate.
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$ certificate management
(I) The functions that a CA may perform during the life cycle of a
digital certificate, including the following:
- Acquire and verify data items to bind into the certificate.
- Encode and sign the certificate.
- Store the certificate in a directory or repository.
- Renew, rekey, and update the certificate.
- Revoke the certificate and issue a CRL.
(See: archive management, certificate management, key management,
security architecture, token management.)
$ certificate management authority (CMA)
(D) /U.S. DoD/ Used to mean either a CA or an RA. [DoD3, SP32]
Deprecated Term: ISDs SHOULD NOT use this term because it is
potentially ambiguous, such as in a context involve ICRLs.
Instead, use CA, RA, or both, depending on what is meant.
$ certificate owner
(D) Synonym for "certificate subject". (See: certificate holder.)
Deprecated Term: ISDs SHOULD NOT use this term as a synonym for
the subject of a digital certificate; the term is potentially
ambiguous. For example, the term could refer to a system entity,
such as a corporation, that has acquired a certificate to operate
equipment, such as a Web server.
$ certificate path
(D) Synonym for "certification path".
Deprecated Term: ISDs SHOULD NOT use this term; it looks like
sloppy use of "certification path", which is the term standardized
by X.509. A person who uses this term probably has not read the
PKI standards [X509, R2459].
$ certificate policy
(I) "A named set of rules that indicates the applicability of a
certificate to a particular community and/or class of application
with common security requirements." [X509] (Compare: CPS.)
Example: The U.S. DoD's certificate policy [DoD3] defines four
classes (i.e., assurance levels) for X.509 public-key certificates
and defines the applicability of those classes. (See: class 2.)
Tutorial: A certificate policy can help a certificate user to
decide whether a certificate should be trusted in a particular
application. "For example, a particular certificate policy might
indicate applicability of a type of certificate for the
authentication of electronic data interchange transactions for the
trading of goods within a given price range." [R2527]
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A v3 X.509 public-key certificate may have a "certificatePolicies"
extension that lists certificate policies, recognized by the
issuing CA, that apply to the certificate and govern its use. Each
policy is denoted by an object identifier and may optionally have
certificate policy qualifiers. (See: certificate profile.)
Each SET certificate specifies at least one certificate policy,
that of the SET root CA. SET uses certificate policy qualifiers to
point to the actual policy statement and to add qualifying
policies to the root policy. (See: SET qualifier.)
$ certificate policy qualifier
(I) Information that pertains to a certificate policy and is
included in a "certificatePolicies" extension in a v3 X.509
public-key certificate.
$ certificate profile
(I) A specification (e.g., [DoD3, R2459]) of the format and
semantics of public-key certificates or attribute certificates,
constructed for use in a specific application context by selecting
from among options offered by a broader standard.
$ certificate reactivation
(I) The act or process by which a digital certificate, which a CA
has designated for revocation but not yet listed on a CRL, is
returned to the valid state.
$ certificate rekey
1. (I) The act or process by which an existing public-key
certificate has its key value changed by issuing a new certificate
with a different (usually new) public key. (See: certificate
renewal, certificate update, rekey.)
Tutorial: For an X.509 public-key certificate, the essence of
rekey is that the subject stays the same and a new public key is
bound to that subject. Other changes are made, and the old
certificate is revoked, only as required by the PKI and CPS in
support of the rekey. If changes go beyond that, the process is a
"certificate update".
2. (O) /MISSI/ The act or process by which a MISSI CA creates a
new X.509 public-key certificate that is identical to the old one,
except the new one has (a) a new, different KEA key or (b) a new,
different DSS key or (c) new, different KEA and DSS keys. The new
certificate also has a different serial number and may have a
different validity period. A new key creation date and maximum key
lifetime period are assigned to each newly generated key. If a new
KEA key is generated, that key is assigned a new KMID. The old
certificate remains valid until it expires, but may not be further
renewed, rekeyed, or updated.
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$ certificate renewal
(I) The act or process by which the validity of the binding
asserted by an existing public-key certificate is extended in time
by issuing a new certificate. (See: certificate rekey, certificate
update.)
Tutorial: For an X.509 public-key certificate, this term means
that the validity period is extended (and, of course, a new serial
number is assigned) but the binding of the public key to the
subject and to other data items stays the same. The other data
items are changed, and the old certificate is revoked, only as
required by the PKI and CPS to support the renewal. If changes go
beyond that, the process is a "certificate rekey" or "certificate
update".
$ certificate request
(D) Synonym for "certification request".
Deprecated Term: ISDs SHOULD NOT use this term; it looks like
imprecise use of a term standardized by PKCS #10 and used in PKIX.
Instead, use "certification request".
$ certificate revocation
(I) The event that occurs when a CA declares that a previously
valid digital certificate issued by that CA has become invalid;
usually stated with a effective date.
Tutorial: In X.509, a revocation is announced to potential
certificate users by issuing a CRL that mentions the certificate.
Revocation and listing on a CRL is only necessary prior to the
certificate's scheduled expiration.
$ certificate revocation list (CRL)
1. (I) A data structure that enumerates digital certificates that
have been invalidated by their issuer prior to when they were
scheduled to expire. (See: certificate expiration, delta CRL,
X.509 certificate revocation list.)
2. (O) "A signed list indicating a set of certificates that are no
longer considered valid by the certificate issuer. In addition to
the generic term CRL, some specific CRL types are defined for CRLs
that cover particular scopes." [X509]
$ certificate revocation tree
(I) A mechanism for distributing notice of certificate
revocations; uses a tree of hash results that is signed by the
tree's issuer. Offers an alternative to issuing a CRL, but is not
supported in X.509. (See: certificate status responder.)
$ certificate serial number
1. (I) An integer value that (a) is associated with, and may be
carried in, a digital certificate; (b) is assigned to the
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certificate by the certificate's issuer; and (c) is unique among
all the certificates produced by that issuer.
2. (O) "An integer value, unique within the issuing CA, which is
unambiguously associated with a certificate issued by that CA."
[X509]
$ certificate status authority
(D) /U.S. DoD/ "A trusted entity that provides on-line
verification to a Relying Party of a subject certificate's
trustworthiness [should say 'validity'], and may also provide
additional attribute information for the subject certificate."
[DoD3]
Deprecated Term: ISDs SHOULD NOT use this term because it is not
widely accepted; instead, use "certificate status responder" or
"OCSP server", or otherwise explain what is meant.
$ certificate status responder
(N) /FPKI/ A trusted on-line server that acts for a CA to provide
authenticated certificate status information to certificate users
[FPKI]. Offers an alternative to issuing a CRL, but is not
supported in X.509. (See: certificate revocation tree, OCSP.)
$ certificate update
(I) The act or process by which non-key data items bound in an
existing public-key certificate, especially authorizations granted
to the subject, are changed by issuing a new certificate. (See:
certificate rekey, certificate renewal.)
Usage: For an X.509 public-key certificate, the essence of this
process is that fundamental changes are made in the data that is
bound to the public key, such that it is necessary to revoke the
old certificate. (Otherwise, the process is only a "certificate
rekey" or "certificate renewal".)
$ certificate user
1. (I) A system entity that depends on the validity of information
(such as another entity's public key value) provided by a digital
certificate. (See: relying party.)
2. (O) "An entity that needs to know, with certainty, the public
key of another entity." [X509]
Usage: The system entity may be a human being or an organization,
or a device or process controlled by a human or organization.
(See: user.)
3. (D) Synonym for "certificate subject".
Deprecated Definition: ISDs SHOULD NOT use this term with this
meaning; the term could be confused with one of the other two
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definitions given above.
$ certificate validation
1. (I) An act or process by which a certificate user establishes
that the assertions made by a digital certificate can be trusted.
(See: valid certificate, validate vs. verify.)
2. (O) "The process of ensuring that a certificate was valid at a
given time, including possibly the construction and processing of
a certification path, and ensuring that all certificates in that
path were valid (i.e. were not expired or revoked) at that given
time." [X509]
Tutorial: To validate a certificate, a certificate user checks
that the certificate is properly formed and signed and is
currently in force:
- Checks the syntax and semantics: Parses the certificate's
syntax and interprets its semantics, applying rules specified
for and by its data fields, such as for critical extensions in
an X.509 certificate.
- Checks the signature: Uses the issuer's public key to verify
the digital signature of the CA who issued the certificate in
question. If the verifier obtains the issuer's public key from
the issuer's own public-key certificate, that certificate
should be validated, too. That validation may lead to yet
another certificate to be validated, and so on. Thus, in
general, certificate validation involves discovering and
validating a certification path.
- Checks currency and revocation: Verifies that the certificate
is currently in force by checking that the current date and
time are within the validity period (if that is specified in
the certificate) and that the certificate is not listed on a
CRL or otherwise announced as invalid. (CRLs themselves require
a similar validation process.)
$ certification
1. (I) /information system/ Comprehensive evaluation (usually made
in support of an accreditation action) of an information system's
technical security features and other safeguards to establish the
extent to which the system's design and implementation meet a set
of specified security requirements. [C4009, FP102, SP37] (See:
accreditation. Compare: evaluation.)
2. (I) /digital certificate/ The act or process of vouching for
the truth and accuracy of the binding between data items in a
certificate. (See: certify.)
3. (I) /PKI/ The act or process of vouching for the ownership of a
public key by issuing a public-key certificate that binds the key
to the name of the entity that possesses the matching private key.
In addition to binding a key with a name, a public-key certificate
may bind those items with other restrictive or explanatory data
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items. (See: X.509 public-key certificate.)
4. (O) /SET/ "The process of ascertaining that a set of
requirements or criteria has been fulfilled and attesting to that
fact to others, usually with some written instrument. A system
that has been inspected and evaluated as fully compliant with the
SET protocol by duly authorized parties and process would be said
to have been certified compliant." [SET2]
$ certification authority (CA)
1. (I) An entity that issues digital certificates (especially
X.509 certificates) and vouches for the binding between the data
items in a certificate.
2. (O) "An authority trusted by one or more users to create and
assign certificates. Optionally the certification authority may
create the user's keys." [X509]
Tutorial: Certificate users depend on the validity of information
provided by a certificate. Thus, a CA should be someone that
certificate users trust, and usually holds an official position
created and granted power by a government, a corporation, or some
other organization. A CA is responsible for managing the life
cycle of certificates (see: certificate management) and, depending
on the type of certificate and the CPS that applies, may be
responsible for the life cycle of key pairs associated with the
certificates (see: key management).
$ certification authority workstation (CAW)
(O) A computer system that enables a CA to issue digital
certificates and supports other certificate management functions
as required.
$ certification hierarchy
1. (I) A tree-structured (loop-free) topology of relationships
among CAs and the entities to whom the CAs issue public-key
certificates. (See: hierarchical PKI, hierarchy management.)
Tutorial: In this structure, one CA is the top CA, the highest
level of the hierarchy. (See: root, top CA.) The top CA may issue
public-key certificates to one or more additional CAs that form
the second-highest level. Each of these CAs may issue certificates
to more CAs at the third highest level, and so on. The CAs at the
second-lowest level issue certificates only to non-CA entities
that form the lowest level (see: end entity). Thus, all
certification paths begin at the top CA and descend through zero
or more levels of other CAs. All certificate users base path
validations on the top CA's public key.
2. (O) /MISSI/ A certification hierarchy for MISSI has three or
four levels of CAs:
- A CA at the highest level, the top CA, is a "policy approving
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authority".
- A CA at the second-highest level is a "policy creation
authority".
- A CA at the third-highest level is a local authority called a
"certification authority".
- A CA at the fourth-highest (optional) level is a "subordinate
certification authority".
3. (O) /PEM/ A certification hierarchy for PEM has three levels of
CAs [R1422]:
- The highest level is the "Internet Policy Registration
Authority".
- A CA at the second-highest level is a "policy certification
authority".
- A CA at the third-highest level is a "certification authority".
4. (O) /SET/ A certification hierarchy for SET has three or four
levels of CAs:
- The highest level is a "SET root CA".
- A CA at the second-highest level is a "brand certification
authority".
- A CA at the third-highest (optional) level is a "geopolitical
certification authority".
- A CA at the fourth-highest level is a "cardholder CA", a
"merchant CA", or a "payment gateway CA".
$ certification path
1. (I) An ordered sequence of public-key certificates (or a
sequence of public-key certificates followed by one attribute
certificate) that enables a certificate user to verify the
signature on the last certificate in the path, and thus enables
the user to obtain a certified public key (or certified
attributes) of the entity that is the subject of that last
certificate. (See: certificate validation, valid certificate.)
2. (O) "An ordered sequence of certificates of objects in the
[X.500 Directory Information Tree] which, together with the public
key of the initial object in the path, can be processed to obtain
that of the final object in the path." [R2527, X509]
Tutorial: The path is the "list of certificates needed to allow a
particular user to obtain the public key of another." [X509] The
list is "linked" in the sense that the digital signature of each
certificate (except the first) is verified by the public key
contained in the preceding certificate; i.e., the private key used
to sign a certificate and the public key contained in the
preceding certificate form a key pair owned by the entity that
signed.
In the X.509 quotation in the previous paragraph, the word
"particular" points out that a certification path that can be
validated by one certificate user might not be able to be
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validated by another. That is because either the first certificate
should be a trusted certificate (it might be a root certificate)
or the signature on the first certificate should be verified by a
trusted key (it might be a root key), but such trust is defined
relative to each user, not absolutely for all users.
$ certification policy
(D) Synonym for either "certificate policy" or "certification
practice statement".
Deprecated Term: ISDs SHOULD NOT use this term as a synonym for
either of the terms given here. Instead, use either "certificate
policy" or "certification practice statement", depending on what
is meant.
$ certification practice statement (CPS)
(I) "A statement of the practices which a certification authority
employs in issuing certificates." [ABA96, R2527] (See: certificate
policy.)
Tutorial: A CPS is a published security policy that can help a
certificate user to decide whether a certificate issued by a
particular CA can be trusted enough to use in a particular
application. A CPS may be (a) a declaration by a CA of the details
of the system and practices it uses in its certificate management
operations, (b) part of a contract between the CA and an entity to
whom a certificate is issued, (c) a statute or regulation
applicable to the CA, or (d) a combination of these types
involving multiple documents. [ABA]
A CPS is usually more detailed and procedurally oriented than a
certificate policy. A CPS applies to a particular CA or CA
community, while a certificate policy applies across CAs or
communities. A CA with its single CPS may support multiple
certificate policies, which may be used for different application
purposes or by different user communities. On the other hand,
multiple CAs, each with a different CPS, may support the same
certificate policy. [R2527]
$ certification request
(I) A algorithm-independent transaction format, defined by PCKS
#10 and used in PKIX, that contains a DN, a public key, and
optionally a set of attributes, collectively signed by the entity
requesting certification, and sent to a CA, which transforms the
request to an X.509 public-key certificate or another type of
certificate.
$ certify
1. (I) Issue a digital certificate and thus vouch for the truth,
accuracy, and binding between data items in the certificate (e.g.,
see: X.509 public-key certificate), such as the identity of the
certificate's subject and the ownership of a public key. (See:
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certification.)
Usage: To "certify a public key" means to issue a public-key
certificate that vouches for the binding between the certificate's
subject and the key.
2. (I) The act by which a CA uses measures to verify the truth,
accuracy, and binding between data items in a digital certificate.
Tutorial: A description of the measures used for verification
should be included in the CA's CPS.
$ CFB
(N) See: cipher feedback.
$ chain
(D) See: trust chain.
$ Challenge Handshake Authentication Protocol (CHAP)
(I) A peer entity authentication method for PPP, using a randomly-
generated challenge and requiring a matching response that depends
on a cryptographic hash of some combination of the challenge and a
secret key. [R1994] (See: challenge-response, PAP.)
$ challenge-response
(I) An authentication process that verifies an identity by
requiring correct authentication information to be provided in
response to a challenge. In a computer system, the authentication
information is usually a value that is required to be computed in
response to an unpredictable challenge value, but it might be just
password.
$ Challenge-Response Authentication Mechanism (CRAM)
(I) IMAP4 usage: A mechanism [R2195], intended for use with IMAP4
AUTHENTICATE, by which an IMAP4 client uses a keyed hash [R2104]
to authenticate itself to an IMAP4 server. (See: POP3 APOP.)
Tutorial: The server includes a unique timestamp in its ready
response to the client. The client replies with the client's name
and the hash result of applying MD5 to a string formed from
concatenating the timestamp with a shared secret that is known
only to the client and the server.
$ channel
1. (I) An information transfer path within a system. (See: covert
channel.)
2. (I) A subdivision of a physical medium allowing possibly shared
independent uses of the medium. [R3753]
$ channel capacity
(I) The total capacity of a link to carry information; usually
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expressed in bits per second. [R3753](Compare: bandwidth.)
Tutorial: Within a given bandwidth, the theoretical maximum
channel capacity is given by Shannon~Os Law. The actual channel
capacity is determined by the bandwidth, the coding system used,
and the signal-to-noise ratio.
$ CHAP
(I) See: Challenge Handshake Authentication Protocol.
$ checksum
(I) A value that (a) is computed by a function that is dependent
on the contents of a data object and (b) is stored or transmitted
together with the object, for the purpose of detecting changes in
the data. (See: cyclic redundancy check, data integrity service,
error detection code, hash, keyed hash, protected checksum.)
Tutorial: To gain confidence that a data object has not been
changed, an entity that later uses the data can compute a checksum
value and compare it with the value that was stored or transmitted
with the object.
Computer systems and networks use checksums (and other mechanisms)
to detect accidental changes in data. However, active wiretapping
that changes data could also change an accompanying checksum to
match the changed data. Thus, some checksum functions by
themselves are not good countermeasures for active attacks. To
protect against active attacks, the checksum function needs to be
well-chosen (see: cryptographic hash), and the checksum result
needs to be cryptographically protected (see: digital signature,
keyed hash).
$ Chinese wall policy
(I) A security policy to prevent conflict of interest caused by an
entity (e.g., a consultant) interacting with competing firms.
(See: Brewer-Nash model.)
Tutorial: All information is categorized into mutually exclusive
conflict-of-interest classes I(1), I(2), ..., I(M), and each firm
F(1), F(2), ..., F(N) belongs to exactly one class. The policy
states that if a consultant has access to class I(i) information
from a firm in that class, then the consultant may not access
information from another firm in that same class, but may access
information from another firm that is in a different class. Thus,
the policy creates a barrier to communication between firms that
are in the same conflict-of-interest class. Brewer and Nash
modeled enforcement of this policy [BN89], including dealing with
policy violations that could occur because two or more consultants
work for the same firm.
$ chosen-ciphertext attack
(I) A cryptanalysis technique in which the analyst tries to
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determine the key from knowledge of plain text that corresponds to
cipher text selected (i.e., dictated) by the analyst.
$ chosen-plaintext attack
(I) A cryptanalysis technique in which the analyst tries to
determine the key from knowledge of cipher text that corresponds
to plain text selected (i.e., dictated) by the analyst.
$ CIAC
(O) See: Computer Incident Advisory Capability.
$ CIK
(I) See: cryptographic ignition key.
$ cipher
(I) A cryptographic algorithm for encryption and decryption.
$ cipher block chaining (CBC)
(N) A block cipher mode that enhances ECB mode by chaining
together blocks of cipher text it produces. [FP081] (See: [R1829],
[R2405], [R2451].)
Tutorial: This mode operates by combining (exclusive OR-ing) the
algorithm's ciphertext output block with the next plaintext block
to form the next input block for the algorithm.
$ cipher feedback (CFB)
(N) A block cipher mode that enhances ECB mode by chaining
together the blocks of cipher text it produces and operating on
plaintext segments of variable length less than or equal to the
block length. [FP081]
Tutorial: This mode operates by using the previously generated
ciphertext segment as the algorithm's input (i.e., by "feeding
back" the cipher text) to generate an output block, and then
combining (exclusive OR-ing) that output block with the next
plaintext segment (block length or less) to form the next
ciphertext segment.
$ cipher text
1. (I) /noun/ Data that has been transformed by encryption so that
its semantic information content (i.e., its meaning) is no longer
intelligible or directly available. (See: ciphertext. Compare:
clear text, plain text.)
2. (O) "Data produced through the use of encipherment. The
semantic content of the resulting data is not available." [I7498
Part 2]
$ ciphertext
1a. (I) /adjective/ Referring to cipher text. (See: cipher text.)
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1b. (D) /noun/ A synonym for cipher text. (See: cleartext,
plaintext.)
Deprecated Usage: To avoid ambiguity, ISDs SHOULD differentiate
between the noun phrase "cipher text" and the adjective
"ciphertext".
$ ciphertext auto-key (CTAK)
(D) "Cryptographic logic that uses previous cipher text to
generate a key stream." [C4009, A1523] (See: KAK.)
Deprecated Term: IDS should not use this term; it is neither well-
known nor precisely defined. Instead, use terms associated with
modes that are defined in standards, such as CBC, CFB, and OFB.
$ ciphertext-only attack
(I) A cryptanalysis technique in which the analyst tries to
determine the key solely from knowledge of intercepted cipher text
(although the analyst may also know other clues, such as the
cryptographic algorithm, the language in which the plain text was
written, the subject matter of the plain text, and some probable
plaintext words.)
$ ciphony
(O) The process of encrypting audio information.
$ CIPSO
(I) See: Common IP Security Option.
$ CKL
(I) See: compromised key list.
$ Clark-Wilson model
(N) A security model [Clark] to maintain data integrity in the
commercial world. (Compare: Bell-LaPadula model.)
$ class 2, 3, 4, 5
(O) /U.S. DoD/ Assurance levels for PKIs, and for X.509 public-key
certificates issued by a PKI. [DoD3] (See: (first law under)
Courtney's laws.)
- "Class 2": Intended for applications handling unclassified,
low-value data in minimally or moderately protected
environments.
- "Class 3": Intended for applications handling unclassified,
medium-value data in moderately protected environments, or
handling unclassified or high-value data in highly protected
environments, and for discretionary access control of
classified data in highly protected environments.
- "Class 4": Intended for applications handling unclassified,
high-value data in minimally protected environments.
- "Class 5": Intended for applications handling classified data
in minimally protected environments, and for authentication of
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material that would affect the security of classified systems.
The environments are defined as follows:
- "Highly protected environment": Networks that are protected
either with encryption devices approved by NSA for protection
of classified data or via physical isolation, and that are
certified for processing system-high classified data, where
exposure of unencrypted data is limited to U.S. citizens
holding appropriate security clearances.
- "Moderately protected environment":
-- Physically isolated unclassified, unencrypted networks in
which access is restricted based on legitimate need.
-- Networks protected by NSA-approved, type 1 encryption,
accessible by U.S.-authorized foreign nationals.
- "Minimally protected environments": Unencrypted networks
connected to either the Internet or NIPRNET, either directly or
via a firewall.
$ Class D computer system
(O) See: TCSEC.
$ classification
(I) A grouping of classified information to which a hierarchical,
restrictive security label is applied to increase protection of
the data from unauthorized disclosure. (See: classified, data
confidentiality service. Compare: compartment.)
Usage: Usually understood to involve data confidentiality, but
ISDs SHOULD make this clear when data also is sensitive in other
ways and SHOULD use other terms for those other sensitivity
concepts. (See: sensitive information, data integrity.)
$ classification label
(I) A security label that tells the degree of harm that will
result from unauthorized disclosure of the labeled data, and may
also tell what countermeasures are required to be applied to
protect the data from unauthorized disclosure. Example: IPSO.
(See: classified, data confidentiality service. Compare: integrity
label.)
Usage: Usually understood to involve data confidentiality, but
ISDs SHOULD make this clear when data also is sensitive in other
ways and SHOULD use other terms for those other sensitivity
concepts. (See: sensitive information, data integrity.)
$ classification level
(I) A hierarchical level of protection (against unauthorized
disclosure) that is required to be applied to certain classified
data. (See: classified. Compare: security level.)
Usage: Usually understood to involve data confidentiality, but
ISDs SHOULD make this clear when data also is sensitive in other
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ways and SHOULD use other terms for those other sensitivity
concepts. (See: sensitive information, data integrity.)
$ classified
1. (I) Refers to information (stored or conveyed, in any form)
that is formally required by a security policy to receive data
confidentiality service and to be marked with a security label
(which in some cases might be implicit) to indicate its protected
status. (See: classification, classification level. Compare:
unclassified.)
Usage: Usually understood to involve data confidentiality, but
ISDs SHOULD make this clear when data also is sensitive in other
ways and SHOULD use other terms for those other sensitivity
concepts. (See: sensitive information, data integrity.)
Tutorial: The term is mainly used in government, especially in the
military, but the underlying concept also applies outside
government.
2. (O) /U.S. DoD/ Information that has been determined pursuant to
Executive Order 12958 ("Classified National Security Information",
20 April 1995) or any predecessor order to require protection
against unauthorized disclosure and is marked to indicate its
classified status when in documentary form.
$ clean system
(I) A computer system in which the operating system and
application system software and files have been freshly installed
from trusted software distribution media. (Compare: secure state.)
$ clear
(D) /verb/ Synonym for "erase". [C4009]
Deprecated Definition: ISDs SHOULD NOT use the term with this
definition; it could be confused with "clear text" in which
information is directly recoverable.
$ clear text
1. (I) /noun/ Data in which the semantic information content
(i.e., the meaning) is intelligible or is directly available,
i.e., not encrypted. (Compare: cipher text, plain text. See:
cleartext, in the clear.)
2. (O) "Intelligible data, the semantic content of which is
available." [I7498 Part 2]
3. (D) Synonym for "plain text".
Deprecated Definition: ISDs SHOULD NOT use this term as a synonym
for "plain text", because the plain text that is input to an
encryption process may itself be cipher text that was output from
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an encryption. (See: superencryption.)
$ clearance
See: security clearance.
$ clearance level
(I) The security level of information to which a security
clearance authorizes a person to have access.
$ cleartext
1a. (I) /adjective/ Referring to clear text. (Compare: ciphertext,
plaintext. See: clear text.)
Usage: To avoid ambiguity, ISDs SHOULD distinguish between the
adjective "cleartext" and the noun phrase "clear text".
$ CLEF
(N) See: commercially licensed evaluation facility.
$ client
(I) A system entity that requests and uses a service provided by
another system entity, called a "server". (See: server.)
Tutorial: Usually, the requesting entity is a computer process,
and it makes the request on behalf of a human user. In some cases,
the server may itself be a client of some other server.
$ client-server system
(I) A distributed system in which one or more entities, called
clients, request a specific service from one or more other
entities, called servers, that provide the service to the clients.
Example: The Word Wide Web, in which servers provided information
that is requested by clients called browsers.
$ CLIPPER
(N) An integrated microcircuit (in MYK-7x series manufactured by
Mykotronx, Inc.) that implements SKIPJACK, has non-deterministic
random number generator, and supports key escrow. (See: Escrowed
Encryption Standard. Compare: CLIPPER.)
Tutorial: The chip was mainly intended for protecting
telecommunications over the public switched network. The key
escrow scheme for the chip involves a SKIPJACK key that is common
to all chips and that protects the unique serial number of the
chip, and a second SKIPJACK key unique to the chip that protects
all data encrypted by the chip. The second key is escrowed as
split key components held by NIST and the U.S. Treasury
Department.
$ closed security environment
(O) /U.S. DoD/ A system environment that meets both of the
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following conditions: (a) Application developers (including
maintainers) have sufficient clearances and authorizations to
provide an acceptable presumption that they have not introduced
malicious logic. (b) Configuration control provides sufficient
assurance that system applications and the equipment they run on
are protected against the introduction of malicious logic prior to
and during the operation of applications. [NCS04] (See: (first law
under) Courtney's laws. Compare: open security environment.)
$ CMA
(D) See: certificate management authority.
$ CMCS
(O) See: COMSEC Material Control System.
$ CMM
(N) See: Capability Maturity Model.
$ CMS
(I) See: Cryptographic Message Syntax.
$ code
1. (I) A system of symbols used to represent information, which
might originally have some other representation. Examples: ASCII,
BER, country code, Morse code. (See: encode, object code, source
code.)
Deprecated usage: To avoid confusion with definition 1, ISDs
SHOULD NOT use "code" as an abbreviation for "country code",
"cyclic redundancy code", "Data Authentication Code", "error
detection code", or "Message Authentication Code". To avoid
misunderstanding, use the fully qualified term in these other
cases, at least at the point of first usage.
2. (I) /cryptography / An encryption algorithm based on
substitution; i.e., a system for providing data confidentiality by
using arbitrary groups (called "code groups") of letters, numbers,
or symbols to represent units of plain text of varying length.
(See: codebook, cryptography.)
Deprecated Usage: To avoid confusion with definition 1, ISDs
SHOULD NOT use "code" as synonym for (a) "cipher", "hash", or
other words that mean "a cryptographic algorithm"; (b) "cipher
text"; or (c) "encrypt", "hash", or other words that refer to
applying a cryptographic algorithm.
3. (I) An algorithm based on substitution, but used to shorten
messages rather than to conceal their content.
4. (I) /computer programming/ To write computer software. (See:
object code, source code.)
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Deprecated Usage: To avoid confusion with definition 1, ISDs
SHOULD NOT use "code" as an abbreviation for "object code" or
"source code". To avoid misunderstanding, use the fully qualified
term in these other cases, at least at the point of first usage.
$ code book
1. (I) Document containing a systematically arranged list of
plaintext units and their ciphertext equivalents. [C4009]
2. (I) An encryption algorithm that uses a word substitution
technique. [C4009] (See: code, ECB.)
$ code signing
(I) A security mechanism that uses a digital signature to provide
data origin authentication for software that is being distributed
for use. (See: mobile code, trusted distribution.)
$ COI
(I) See: community of interest.
$ cold start
(N) /cryptographic module/ A procedure for initially keying
cryptographic equipment. [C4009]
$ color change
(I) In a system being operated in periods processing mode, the act
of purging all information from one processing period and then
changing over to the next processing period. (See: BLACK, RED.)
$ Commercial COMSEC Endorsement Program (CCEP)
(N) "Relationship between NSA and industry in which NSA provides
the COMSEC expertise (i.e., standards, algorithms, evaluations,
and guidance) and industry provides design, development, and
production capabilities to produce a type 1 or type 2 product."
[C4009]
$ commercially licensed evaluation facility (CLEF)
(N) An organization that has official approval to evaluate the
security of products and systems in accordance with the Common
Criteria, ITSEC, or some other standard.
$ Common Criteria for Information Technology Security
(N) A standard for evaluating information technology (IT) products
and systems. It states requirements for security functions and for
assurance measures. [CCIB] (See: CLEF, EAL, packages, protection
profile, security target, TOE. Compare: CMM.)
Tutorial: Canada, France, Germany, the Netherlands, the United
Kingdom, and the United States (NIST and NSA) began developing
this standard in 1993, based on the European ITSEC, the Canadian
Trusted Computer Product Evaluation Criteria (CTCPEC), and the
U.S. "Federal Criteria for Information Technology Security" and
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its precursor, the TCSEC. Work was done in cooperation with
ISO/IEC Joint Technical Committee 1 (Information Technology),
Subcommittee 27 (Security Techniques), Working Group 3 (Security
Criteria). Version 2.0 of the Criteria has been issued as ISO's
International Standard 15408. The U.S. Government intends this
standard to supersede both the TCSEC and FIPS PUB 140-1. (See:
NIAP.)
The standard addresses data confidentiality, data integrity, and
availability and may apply to other aspects of security. It
focuses on threats to information arising from human activities,
malicious or otherwise, but may apply to non-human threats. It
applies to security measures implemented in hardware, firmware, or
software. It does not apply to (a) administrative security not
related directly to technical security, (b) technical physical
aspects of security such as electromagnetic emanation control, (c)
evaluation methodology or administrative and legal framework under
which the criteria may be applied, (d) procedures for use of
evaluation results, or (e) assessment of inherent qualities of
cryptographic algorithms.
Part 1, Introduction and General Model, defines general concepts
and principles of IT security evaluation; presents a general model
of evaluation; and defines constructs for expressing IT security
objectives, for selecting and defining IT security requirements,
and for writing high-level specifications for products and
systems.
Part 2, Security Functional Requirements, contains a catalog of
well-defined and understood security functional requirements that
are intended to be used as a standard way of expressing the
security requirements for IT products and systems.
Part 3, Security Assurance Requirements, contains a catalog of
assurance components for use as a standard way of expressing the
such requirements for IT products and systems, and defines
evaluation criteria for protection profiles and security targets.
$ Common IP Security Option (CIPSO)
(I) See: (secondary definition under) IPSO.
$ common name
(N) A character string that (a) may be a part of the X.500 DN of a
Directory object ("commonName" attribute), (b) is a (possibly
ambiguous) name by which the object is commonly known in some
limited scope (such as an organization), and (c) conforms to the
naming conventions of the country or culture with which it is
associated. [X520] (See: ("subject" and "issuer" under) X.509
public-key certificate.)
Examples: "Dr. Albert Einstein", "The United Nations", and "12-th
Floor Laser Printer".
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$ communications cover
(N) "Concealing or altering of characteristic communications
patterns to hide information that could be of value to an
adversary." [C4009] (See: operations security, traffic-flow
confidentiality, TRANSEC.)
$ communication security (COMSEC)
(I) Measures that implement and assure security services in a
communication system, particularly those that provide data
confidentiality and data integrity and that authenticate
communicating entities.
Usage: COMSEC is usually understood to include (a) cryptography
and its related algorithms and key management methods and
processes, devices that implement those algorithms and processes,
and the life cycle management of the devices and keying material.
Also, COMSEC is sometimes more broadly understood as further
including (b) traffic-flow confidentiality, (c) TRANSEC, and (d)
steganography [Kahn]. (See: cryptology, signal security.)
$ community of interest (COI)
1. (I) A set of entities that operate under a common security
policy. (Compare: domain.)
2. (O) /U.S. DoD/ "A collaborative group of users who exchange
information in support of shared missions, business processes, and
objectives."
$ community risk
(O) Probability that a particular vulnerability will be exploited
within an interacting population and adversely affect some members
of that population. [C4009]
$ community string
(I) A community name in the form of an octet string that serves as
a cleartext password in SNMP version 1. [R1157]
$ compartment
(I) A grouping of sensitive information items that require special
access controls beyond those normally provided for the basic
classification level of the information. (See: category.)
Usage: The term is usually understood to include the special
handling procedures to be used for the information.
$ Compartments field
(I) A 16-bit field (the "C field") that specifies compartment
values in the security option (option type 130) of version 4 IP's
datagram header format. The valid field values are assigned by the
U.S. Government, as specified in RFC 791.
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Deprecated Definition: ISDs SHOULD NOT use the abbreviation "C
field"; the abbreviation is potentially ambiguous. Instead, use
"Compartments field".
$ component
See: system component.
$ compression
(I) A process that encodes information in a way that minimizes the
number of resulting code symbols and thus reduces storage space or
transmission time.
Tutorial: A data compression algorithm may be "lossless", i.e.,
retain all information that was encoded in the data, so that
decompression can recover all the information; or an algorithm may
be "lossy". Text usually needs to be compressed losslessly, but
images are often compressed with lossy schemes.
Not all schemes that encode information losslessly for machine
processing are efficient in terms of minimizing the number of
output bits. For example, ASCII encoding is lossless, but ASCII
data can often be losslessly reencoded in fewer bits with other
schemes. These more efficient schemes take advantage of some sort
of inherent imbalance, redundancy, or repetition in the data, such
as by replacing a character string in which all characters are the
same by a shorter string consisting of only the single character
and a character count.
Lossless compression schemes cannot effectively reduce the number
of bits in cipher text produced by a strong encryption algorithm,
because the cipher text is essentially a pseudorandom bit string
that does not contain patterns susceptible to reencoding.
Therefore, protocols that offer both encryption and compression
services (e.g., SSL) need to perform the compression operation
before the encryption operation.
$ compromise
See: data compromise, security compromise.
$ compromise recovery
(I) The process of regaining a secure state for a system after
detecting that the system has experienced a security compromise.
$ compromised key list (CKL)
(O) /MISSI/ A list that identifies keys for which unauthorized
disclosure or alteration may have occurred. (See: compromise.)
Tutorial: A CKL is issued by an CA, like a CRL is issued. But a
CKL lists only KMIDs, not subjects that hold the keys, and not
certificates in which the keys are bound.
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$ COMPUSEC
(I) See: computer security.
$ computer emergency response team (CERT)
(I) An organization that studies computer and network INFOSEC in
order to provide incident response services to victims of attacks,
publish alerts concerning vulnerabilities and threats, and offer
other information to help improve computer and network security.
(See: CSIRT, security incident.)
Examples: CERT Coordination Center at Carnegie-Mellon University
(sometimes called "the" CERT); CIAC.
$ Computer Incident Advisory Capability (CIAC)
(O) The centralized CSIRT of the U.S Department of Energy; a
member of FIRST.
$ computer network
(I) A collection of host computers together with the subnetwork or
internetwork through which they can exchange data.
Usage: This definition is intended to cover systems of all sizes
and types, ranging from the complex Internet to a simple system
composed of a personal computer dialing in as a remote terminal of
another computer.
$ computer platform
(I) A combination of computer hardware and an operating system
(which may consist of software, firmware, or both) for that
hardware.
$ computer security (COMPUSEC)
(I) Measures to implement and assure security services in a
computer system, particularly those that assure access control
service.
Usage: Usually refers to internal controls (functions, features,
and technical characteristics) that are implemented in software
(especially in operating systems); sometimes refers to internal
controls implemented in hardware; rarely used to refer to external
controls.
(O) "The protection afforded to an automated information system in
order to attain the applicable objectives of preserving the
integrity, availability and confidentiality of information system
resources (includes hardware, software, firmware,
information/data, and telecommunications)." [SP12]
$ computer security incident response team (CSIRT)
(I) An organization "that coordinates and supports the response to
security incidents that involve sites within a defined
constituency." [R2350] (See: CERT, FIRST, security incident.)
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Tutorial: To be considered a CSIRT, an organization must do as
follows: (a) Provide a (secure) channel for receiving reports
about suspected security incidents. (b) Provide assistance to
members of its constituency in handling the incidents. (c)
Disseminate incident-related information to its constituency and
other involved parties.
$ computer security object
(I) The definition or representation of a resource, tool, or
mechanism used to maintain a condition of security in computerized
environments. Includes many items referred to in standards that
are either selected or defined by separate user communities.
[CSOR] (See: object identifier, Computer Security Objects
Register.)
$ Computer Security Objects Register (CSOR)
(N) A service operated by NIST is establishing a catalog for
computer security objects to provide stable object definitions
identified by unique names. The use of this register will enable
the unambiguous specification of security parameters and
algorithms to be used in secure data exchanges. (See: object
identifier.)
Tutorial: The CSOR follows registration guidelines established by
the international standards community and ANSI. Those guidelines
establish minimum responsibilities for registration authorities
and assign the top branches of an international registration
hierarchy. Under that international registration hierarchy the
CSOR is responsible for the allocation of unique identifiers under
the branch: {joint-iso-ccitt(2) country(16) us(840)
organization(1) gov(101) csor(3)}.
$ Computers At Risk
(O) The 1991 report [NRC91] of the System Security Study
Committee, sponsored by the U.S. National Academy of Sciences and
supported by the Defense Advanced Research Projects Agency of the
U.S. DoD. It made many recommendations for industry and Government
to improve computer security and trustworthiness. Some of the most
important recommendations (e.g., establishing an Information
Security Foundation chartered by the U.S. Government) have not
been implemented at all, and others (e.g., codifying Generally
Accepted System Security Principles similar to accounting
principles) have been implemented but not widely adopted [SP14,
SP27].
$ COMSEC
(I) See: communication security.
$ COMSEC account
(N) /U.S. Government/ "Administrative entity, identified by an
account number, used to maintain accountability, custody, and
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control of COMSEC material." [C4009] (See: COMSEC custodian.)
$ COMSEC accounting
(I) /U.S. Government/ The process of creating, collecting, and
maintaining data records that describe the status and custody of
designated items of COMSEC material. (See: accounting legend
code.)
Tutorial: Almost any secure information system needs to record a
security audit trail, but a system that manages COMSEC material
needs to record additional data about the status and custody of
COMSEC items.
- COMSEC tracking: The process of automatically collecting,
recording, and managing information that describes the status
of designated items of COMSEC material at all times during each
product~Os lifecycle.
- COMSEC controlling: The process of supplementing tracking data
with custody data, which consists of explicit acknowledgements
of system entities that they (a) have received specific COMSEC
items and (b) are responsible for preventing exposure of those
items.
For example, a key management system that serves a large customer
base needs to record tracking data for the same reasons that a
national parcel delivery system does, i.e., to answer the question
"Where is that thing now?". If keys are encrypted immediately upon
generation and handled only in BLACK form between the point of
generation and the point of use, then tracking may be all that is
needed. However, in cases where keys are handled at least partly
in RED form and are potentially subject to exposure, then tracking
needs to be supplemented by controlling.
Data that is used purely for tracking need be retained only
temporarily, until an item's status changes. Data that is used for
controlling is retained indefinitely to ensure accountability and
support compromise recovery.
$ COMSEC boundary
(N) "Definable perimeter encompassing all hardware, firmware, and
software components performing critical COMSEC functions, such as
key generation and key handling and storage." [C4009] [Compare:
cryptographic boundary.]
$ COMSEC custodian
(N) /U.S. Government/ "Individual designated by proper authority
to be responsible for the receipt, transfer, accounting,
safeguarding, and destruction of COMSEC material assigned to a
COMSEC account." [C4009]
$ COMSEC material
(N) /U.S. Government/ "Item designed to secure or authenticate
communications. [It] includes but is not limited to key,
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equipment, devices, documents, firmware, or software that embodies
or describes cryptographic logic and other items that perform
COMSEC functions." [C4009] (Compare: keying material.)
$ COMSEC Material Control System (CMCS)
(O) /U.S. Government/ "Logistics and accounting system through
which COMSEC material marked 'CRYPTO' is distributed, controlled,
and safeguarded." [C4009] (See: COMSEC account, COMSEC custodian.)
$ confidentiality
See: data confidentiality.
$ configuration control
(I) The process of regulating changes to hardware, firmware,
software, and documentation throughout the development and
operational life of a system. (See: administrative security,
trusted distribution.)
Tutorial: Configuration control helps protect against unauthorized
or malicious alteration of a system and thus provides assurance of
system integrity. (See: malicious logic.)
$ confinement property
(N) /formal model/ Property of a system whereby a subject has
write access to an object only if the classification of the object
dominates the clearance of the subject. (See: *-property, Bell-
LaPadula model.)
$ connectionless data integrity service
(I) A security service that provides data integrity service for an
individual IP datagram, by detecting modification of the datagram,
without regard to the ordering of the datagram in a stream of
datagrams.
Tutorial: In contrast, a connection-oriented data integrity
service usually would be able to detect lost or reordered
datagrams within a stream of datagrams.
$ constraint
(I) /access control/ A limitation on the function of an identity,
role, or privilege. (See: rule-based access control.)
Tutorial: In effect, a constraint is a form of security policy and
may be either static or dynamic:
- "Static constraint": A constraint that must be satisfied at the
time the policy is defined, and then continues to be satisfied
until the constraint is removed.
- "Dynamic constraint": A constraint that may be defined to apply
at various times that the identity, role, or other object of
the constraint is active in the system.
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$ content filter
(I) /World Wide Web/ Application software used to prevent access
to certain Web servers, such as by parents who do not want their
children to access pornography. (See: filter, guard.)
Tutorial: The filter is usually browser-based, but could be part
of an intermediate cache server. The two basic content filtering
techniques are (a) to block a specified list of URLs and (b) to
block material that contains specified words and phrases.
$ contingency plan
(I) A plan for emergency response, backup operations, and post-
disaster recovery in a system as part of a security program to
ensure availability of critical system resources and facilitate
continuity of operations in a crisis. [NCS04] (See: availability.)
$ controlled access protection
(N) The C2 level of criteria described in the TCSEC.
Tutorial: The major features of the C2 level are individual
accountability, audit, access control, and object reuse.
$ controlled cryptographic item (CCI)
(O) /U.S. Government/ "Secure telecommunications or information
handling equipment, or associated cryptographic component, that is
unclassified but governed by a special set of control
requirements." [C4009] (Compare: EUCI.)
Tutorial: This category of equipment was established in 1985 to
promote broad use of secure equipment for protecting both
classified and unclassified information in the national interest.
CCI equipment uses a classified cryptographic logic, but the
hardware or firmware embodiment of that logic is unclassified.
Drawings, software implementations, and other descriptions of that
logic remain classified. [N4001]
$ controlled interface
(I) A mechanism that facilitates the adjudication of the different
security policies of interconnected systems. (See: domain, guard.)
$ controlled security mode
(D) /U.S. DoD/ A mode of operation of an information system,
wherein at least some users with access to the system have neither
a security clearance nor need to know for all classified material
contained in the system. However, separation and control of users
and classified material on the basis, respectively, of clearance
and classification level are not essentially under operating
system control like they are in multilevel security mode. [DoD2]
Deprecated Term: ISDs SHOULD NOT use this term. It was defined in
a version of U.S. DoD policy on system accreditation but was
subsumed by "partitioned security mode" in a later version.
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Tutorial: Controlled mode was intended to encourage ingenuity in
meeting the security requirements of Defense policy in ways less
restrictive than "dedicated security mode" and "system high
security mode", but at a level of risk lower than that generally
associated with the true "multilevel security mode". This was to
be accomplished by implementation of explicit augmenting measures
to reduce or remove a substantial measure of system software
vulnerability together with specific limitation of the security
clearance levels of users permitted concurrent access to the
system.
$ controlling authority
(O) /U.S. Government/ "Official responsible for directing the
operation of a cryptonet and for managing the operational use and
control of keying material assigned to the cryptonet." [C4009,
N4006]
$ cookie
1. (I) /HTTP/ Data exchanged between an HTTP server and a browser
(a client of the server) to store state information on the client
side and retrieve it later for server use.
Tutorial: An HTTP server, when sending data to a client, may send
along a cookie, which the client retains after the HTTP connection
closes. A server can use this mechanism to maintain persistent
client-side state information for HTTP-based applications,
retrieving the state information in later connections. A cookie
may include a description of the range of URLs for which the state
is valid. Future requests made by the client in that range will
also send the current value of the cookie to the server. Cookies
can be used to generate profiles of web usage habits, and thus may
infringe on personal privacy.
2. (I) /IPsec/ Data objects exchanged by ISAKMP to prevent certain
denial-of-service attacks during the establishment of a security
association.
3. (D) /access control/ Synonym for "capability" or "ticket.
Deprecated Definition: ISDs SHOULD NOT use this term with this
definition; that would duplicate the meaning of better-established
terms and mix concepts in a potentially misleading way.
$ Coordinated Universal Time (UTC)
(N) UTC is derived from International Atomic Time (TAI) by adding
a number of leap seconds. The International Bureau of Weights and
Measures computes TAI once each month by averaging data from many
laboratories. (See: GeneralizedTime, UTCTime.)
$ copy
See: card copy.
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$ correctness
(I) "The property of a system that is guaranteed as the result of
formal verification activities." [Huff] (See: correctness proof,
verification.)
$ correctness integrity
(I) Accuracy and consistency of the information that data values
represent, rather than of the data itself. Closely related to
issues of accountability and error handling. (See: data integrity,
source integrity.)
$ correctness proof
(I) A mathematical proof of consistency between a specification
for system security and the implementation of that specification.
(See: correctness, formal specification.)
$ corruption
A type of threat action that undesirably alters system operation
by adversely modifying system functions or data. (See:
disruption.)
Usage: This type includes the following subtypes:
- "Tampering": In context of corruption, deliberately altering a
system's logic, data, or control information to interrupt or
prevent correct operation of system functions. (See: (main
entry for) tampering.)
- "Malicious logic": In context of corruption, any hardware,
firmware, or software (e.g., a computer virus) intentionally
introduced into a system to modify system functions or data.
(See: (main entry for) malicious logic.)
- "Human error": In context of corruption, human action or
inaction that unintentionally results in the alteration of
system functions or data.
- "Hardware or software error": In context of corruption, error
that results in the alteration of system functions or data.
- "Natural disaster": In context of corruption, any "act of God"
(e.g., power surge caused by lightning) that alters system
functions or data. [FP031 section 2]
$ counter-countermeasure
(I) An action, device, procedure, or technique used by an attacker
to offset a defensive countermeasure.
Tutorial: For every countermeasure devised to protect computers
and networks, some cracker probably will be able to devise a
counter-countermeasure. Thus, systems must use "defense in depth".
$ countermeasure
(I) An action, device, procedure, or technique that reduces a
threat, a vulnerability, or an attack by eliminating or preventing
it, by minimizing the harm it can cause, or by discovering and
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reporting it so that corrective action can be taken.
Tutorial: In an Internet protocol, a countermeasure may take the
form of a protocol feature, an component function, or a usage
constraint.
$ country code
(I) An identifier that is defined for a nation by ISO. [I3166]
Tutorial: For each nation, ISO Standard 3166 defines a unique two-
character alphabetic code, a unique three-character alphabetic
code, and a three-digit code. Among many uses of these codes, the
two-character codes are used as top-level domain names.
$ Courtney's laws
Tutorial: The following principles for managing system security
were stated by Robert H. Courtney, Jr.: [Murr]
- Courtney's first law: You cannot say anything interesting about
the security of a system except in the context of a particular
application and environment.
- Courtney's second law: Never spend more money eliminating a
security exposure than tolerating it will cost you. (See:
acceptable risk, risk analysis.)
-- First corollary: Perfect security has infinite cost.
-- Second corollary: There is no such thing as zero risk.
- Courtney's third law: There are no technical solutions to
management problems, but there are management solutions to
technical problems.
$ covert action
(I) An operation that is planned and executed in a way that
conceals the identity of the operator.
$ covert channel
1. (I) An unintended or unauthorized intra-system channel that
enables two cooperating entities to transfer information in a way
that violates the system's security policy but does not exceed the
entities' access authorizations. (See: covert storage channel,
covert timing channel, out of band.)
2. (O) "A communications channel that allows two cooperating
processes to transfer information in a manner that violates the
system's security policy." [NCS04]
Tutorial: The cooperating entities can be either two insiders or
an insider and an outsider. Of course, an outsider has no access
authorization at all. A covert channel is a system feature that
the system architects neither designed nor intended for
information transfer.
$ covert storage channel
(I) A system feature that enables one system entity to signal
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information to another entity by directly or indirectly writing a
storage location that is later directly or indirectly read by the
second entity. (See: covert channel.)
$ covert timing channel
(I) A system feature that enable one system entity to signal
information to another by modulating its own use of a system
resource in such a way as to affect system response time observed
by the second entity. (See: covert channel.)
$ CPS
(I) See: certification practice statement.
$ cracker
(I) Someone who tries to break the security of, and gain access
to, someone else's system without being invited. (Compare: hacker.
See: adversary, intruder, packet monkey, script kiddy.)
$ CRAM
(I) See: Challenge-Response Authentication Mechanism.
$ CRC
(I) See: cyclic redundancy check.
$ credential
1. (I) /authentication/ "Identity credential": A data object that
is a portable representation of the association between an
identifier and a unit of authentication information, and that can
be transferred or presented for use in proving a claim of that
identity. Example: X.509 public-key certificate. (See: anonymous
credential.)
2. (I) /access control/ "Authorization credential": A data object
that is a portable representation of the association between an
identifier and one or more access, and that can be transferred or
presented for use when attempting to exercise such access.
Example: X.509 attribute certificate. (See: capability, ticket.)
3. (D) /OSIRM/ "Data that is transferred to establish the claimed
identity of an entity." [I7498 Part 2]
Deprecated Definition: ISDs should not use the term with this
definition. As explained in the tutorial below, an authentication
process can involve the transfer of multiple data objects, and not
all of those are credentials.
4. (D) /U.S. Government/ "An object that is verified when
presented to the verifier in an authentication transaction."
[M0404]
Deprecated Definition: ISDs should not use the term with this
definition; it mixes concepts in a potentially misleading way. For
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example, in an authentication process, it is the identity that is
"verified", not the credential; the credential is "validated".
(See: validate vs. verify.)
Tutorial: In general English, "credentials" are evidence or
testimonials that (a) support a claim of identity or authorization
and (b) usually are intended to be used more than once (i.e., a
credential's life is long compared to the time needed for one
use). Some examples are a policeman's badge, an automobile
driver's license, and a national passport. An authentication or
access control process that uses a badge, license, or passport is
outwardly simple: the holder just shows the thing.
The problem with adopting this term in Internet security is that
an automation authentication or access control process requires
multiple steps using multiple data objects, and it might not be
immediately obvious which of those objects should get the name
"credential".
For example, if the verification step in a user authentication
process employs public-key technology, then the process involves
at least three data items: (a) the user's private key, (b) a
signed value -- signed with that private key and passed to the
system, perhaps in response to a challenge from the system -- and
(c) the user's public-key certificate, which is validated by the
system and provides the public key needed to verify the signature.
- Private key: The private key is *not* a credential, because it
is never transferred or presented. Instead, the private key is
"authentication information", which is associated with the
user's identifier for a specified period of time and can be
used in multiple authentications during that time.
- Signed value: The signed value is *not* a credential; the
signed value is only ephemeral, not long lasting. The OSIRM
definition could be interpreted to call the signed value a
credential, but that would conflict with general English.
- Certificate. The user's certificate *is* a credential. It can
be "transferred" or "presented" to any person or process that
needs it at any time. A public-key certificate may be used as
an "identity credential", and an attribute certificate may be
used as an "authorization credential".
$ critical
1. (I) /system resource/ A condition of a system resource such
that denial of access to, or lack of availability of, that
resource would jeopardize a system user's ability to perform a
primary function or would result in other serious consequences,
such as human injury or loss of life. (See: availability,
precedence. Compare: sensitive.)
2. (N) /extension/ An indication that an application is not
permitted to ignore an extension. [X509]
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Tutorial: Each extension of an X.509 certificate or CRL is flagged
as either "critical" or "non-critical". In a certificate, if a
computer program does not recognize an extension's type (i.e.,
does not implement its semantics), then if the extension is
critical, the program is required to treat the certificate as
invalid; but if the extension is non-critical, the program is
permitted to ignore the extension.
In a CRL, if a program does not recognize a critical extension
that is associated with a specific certificate, the program is
required to assume that the listed certificate has been revoked
and is no longer valid, and then take whatever action is required
by local policy.
When a program does not recognize a critical extension that is
associated with the CRL as whole, the program is required to
assume that all listed certificates have been revoked and are no
longer valid. However, since failing to process the extension may
mean that the list has not been completed, the program cannot
assume that other certificates are valid, and the program needs to
take whatever action is therefore required by local policy.
$ critical information infrastructure
(I) Those systems that are so vital to a nation that their
incapacity or destruction would have a debilitating affect on
national security, the economy, or public health and safety.
$ CRL
(I) See: certificate revocation list.
$ CRL distribution point
(I) See: distribution point.
$ CRL extension
(I) See: extension.
$ cross-certificate
(I) A public-key certificate issued by a CA in one PKI to a CA in
another PKI. (See: cross-certification.)
$ cross-certification
(I) The act or process by which a CA in one PKI issues a public-
key certificate to a CA in another PKI. [X509] (See: bridge CA.)
Tutorial: X.509 says that a CA (say CA1) may issue a "cross-
certificate" in which the subject is another CA (say CA2). X.509
calls CA2 the "subject CA" and calls CA1 an "intermediate CA", but
this Glossary deprecates those terms. (See: intermediate CA,
subject CA).
Cross-certification of CA2 by CA1 appears similar to certification
of a subordinate CA by a superior CA, but cross-certification
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involves a different concept. The "subordinate CA" concept applies
when both CAs are in the same PKI, i.e., when either (a) CA1 and
CA2 are under the same root or (b) CA1 is itself a root. The
"cross-certification" concept applies in other cases:
First, cross-certification applies when two CAs are in different
PKIs, i.e., when CA1 and CA2 are under different roots, or perhaps
are both roots themselves. Issuing the cross-certificate enables
end entities certified under CA1 in PK1 to construct the
certification paths needed to validate the certificates of end
entities certified under CA2 in PKI2. Sometimes, a pair of cross-
certificates is issued -- by CA1 to CA2, and by CA2 to CA1 -- so
that an end entity in either PKI can validate certificates issued
in the other PKI.
Second, X.509 says that two CAs in some complex, multi-CA PKI can
cross-certify one another for the purpose of shortening the
certification paths constructed by end entities. Whether or not a
CA may perform this or any other form of cross-certification, and
how such certificates may be used by end entities, should be
addressed by the local certificate policy and CPS.
$ cryptanalysis
1. (I) The mathematical science that deals with analysis of a
cryptographic system in order to gain knowledge needed to break or
circumvent the protection that the system is designed to provide.
(See: cryptology.)
2. (O) "The analysis of a cryptographic system and/or its inputs
and outputs to derive confidential variables and/or sensitive data
including cleartext." [I7498 Part 2]
Tutorial: Definition 2 states the traditional goal of
cryptanalysis, i.e. convert cipher text to plain text (which
usually is clear text) without knowing the key; but that
definition applies only to encryption systems. Today, the term is
used with reference to all kinds of cryptographic algorithms and
key management, and definition 1 reflects that. In all cases,
however, a cryptanalyst tries to uncover or reproduce someone
else's sensitive data, such as clear text, a key, or an algorithm.
The basic cryptanalytic attacks on encryption systems are
ciphertext-only, known-plaintext, chosen-plaintext, and chosen-
ciphertext; and these generalize to the other kinds of
cryptography.
$ crypto, CRYPTO
1. (N) A prefix ("crypto-") that means "cryptographic".
Usage: ISDs MAY use this prefix when it part of a term listed in
this Glossary. Otherwise, ISDs SHOULD avoid this prefix; instead,
use the adjective "cryptographic".
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2. (D) /slang/ In lower case, "crypto" is a synonym for the
adjective "cryptographic", or for the nouns "cryptography" or
"cryptographic component".
Deprecated Term: ISDs SHOULD NOT use this slang term; it could be
misunderstood.
3. (O) /U.S. Government/ In upper case, "CRYPTO" is a marking or
designator that identifies "COMSEC keying material used to secure
or authenticate telecommunications carrying classified or
sensitive U.S. Government or U.S. Government-derived information."
[C4009]
$ cryptographic
(I) An adjective that refers to cryptography.
$ cryptographic algorithm
(I) An algorithm that uses the science of cryptography, including
(a) encryption algorithms, (b) cryptographic hash algorithms, (c)
digital signature algorithms, and (d) key agreement algorithms.
$ cryptographic application programming interface (CAPI)
(I) The source code formats and procedures through which an
application program accesses cryptographic services, which are
defined abstractly compared to their actual implementation.
Example, see: PKCS #11, [R2628].
$ cryptographic association
(I) A security association that involves the use of cryptography
to provide security services for data exchanged by the associated
entities. (See: ISAKMP.)
$ cryptographic boundary
(I) See: (secondary definition under) cryptographic module.
$ cryptographic card
(I) A cryptographic token in the form of a smart card or a PC
card.
$ cryptographic component
(I) A generic term for any system component that involves
cryptography. (See: cryptographic module.)
$ cryptographic hash
(I) See: (secondary definition under) hash function.
$ cryptographic ignition key (CIK)
1. (I) A physical (usually electronic) token used to store,
transport, and protect cryptographic keys. Usage: Sometimes
abbreviated as "crypto-ignition key". (Compare: fill device.)
Tutorial: A typical use is to divide a split key between a CIK and
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a cryptographic module, so that it is necessary to combine the two
to regenerate a key-encrypting key and thus activate the module
and other keys it contains.
2. (O) "Device or electronic key used to unlock the secure mode of
cryptographic equipment." [C4009]
$ cryptographic key
(I) See: key. Usage: Usually shortened to just "key".
$ Cryptographic Message Syntax (CMS)
(I) An encapsulation syntax (RFC 3852) for digital signatures,
hashes, and encryption of arbitrary messages.
Tutorial: CMS derives from PKCS #7. CMS values are specified with
ASN.1 and use BER encoding. The syntax permits multiple
encapsulation with nesting, permits arbitrary attributes to be
signed along with message content, and supports a variety of
architectures for digital certificate-based key management.
$ cryptographic module
(I) A set of hardware, software, firmware, or some combination
thereof that implements cryptographic logic or processes,
including cryptographic algorithms, and is contained within the
module's "cryptographic boundary", which is an explicitly defined
contiguous perimeter that establishes the physical bounds of the
module. [FP140]
$ cryptographic system
1. (I) A set of cryptographic algorithms together with the key
management processes that support use of the algorithms in some
application context.
Usage: ISDs SHOULD use definition 1 because it covers a wider
range of algorithms than definition 2.
2. (O) "A collection of transformations from plain text into
cipher text and vice versa [which would exclude digital signature,
cryptographic hash, and key agreement algorithms], the particular
transformation(s) to be used being selected by keys. The
transformations are normally defined by a mathematical algorithm."
[X509]
$ cryptographic token
1. (I) A portable, user-controlled, physical device (e.g., smart
card or PCMCIA card) used to store cryptographic information and
possibly also perform cryptographic functions. (See: cryptographic
card, token.)
Tutorial: A smart token might implement some set of cryptographic
algorithms and might incorporate related key management functions,
such as a random number generator. A smart cryptographic token may
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contain a cryptographic module or may not be explicitly designed
that way.
$ cryptography
1. (I) The mathematical science that deals with transforming data
to render its meaning unintelligible (i.e., to hide its semantic
content), prevent its undetected alteration, or prevent its
unauthorized use. If the transformation is reversible,
cryptography also deals with restoring encrypted data to
intelligible form. (See: cryptology, steganography.)
2. (O) "The discipline which embodies principles, means, and
methods for the transformation of data in order to hide its
information content, prevent its undetected modification and/or
prevent its unauthorized use ... . Cryptography determines the
methods used in encipherment and decipherment." [I7498 Part 2]
Tutorial: Comprehensive coverage of applied cryptographic
protocols and algorithms is provided by Schneier [Schn].
Businesses and governments use cryptography to make data
incomprehensible to outsiders; to make data incomprehensible to
both outsiders and insiders, the data is sent to lawyers for a
rewrite.
$ Cryptoki
(N) See: (secondary definition under) PKCS #11.
$ cryptology
(I) The science of secret communication, that includes both
cryptography and cryptanalysis.
Tutorial: Sometimes the term is used more broadly to denote
activity that includes both rendering signals secure (see: signal
security) and extracting information from signals (see: signal
intelligence) [Kahn].
$ cryptonet
(I) A network (i.e., a communicating set) of system entities that
share a secret cryptographic key for a symmetric algorithm. (See:
controlling authority.)
(O) "Stations holding a common key." [C4009]
$ cryptoperiod
(I) The time span during which a particular key value is
authorized to be used in a cryptographic system. (See: key
management.)
Usage: This term is long-established in COMPUSEC usage. In the
context of certificates and public keys, "key lifetime" and
"validity period" are often used instead.
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Tutorial: A cryptoperiod is usually stated in terms of calendar or
clock time, but sometimes is stated in terms of the maximum amount
of data permitted to be processed by a cryptographic algorithm
using the key. Specifying a cryptoperiod involves a tradeoff
between the cost of rekeying and the risk of successful
cryptoanalysis.
$ cryptosystem
(I) Contraction of "cryptographic system".
$ cryptovariable
(D) Synonym for "key".
Deprecated Usage: In contemporary COMSEC usage, the term "key" has
replaced the term "cryptovariable".
$ CSIRT
(I) See: computer security incident response team.
$ CSOR
(N) See: Computer Security Objects Register.
$ CTAK
(D) See: ciphertext auto-key.
$ cut-and-paste attack
(I) An active attack on the data integrity of cipher text,
effected by replacing sections of cipher text with other cipher
text, such that the result appears to decrypt correctly but
actually decrypts to plain text that is forged to the satisfaction
of the attacker.
$ cyclic redundancy check (CRC)
(I) A type of checksum algorithm that is not a cryptographic hash
but is used to implement data integrity service where accidental
changes to data are expected. Sometimes called "cyclic redundancy
code".
$ DAC
(N) See: Data Authentication Code, discretionary access control.
Deprecated Usage: This abbreviation is ambiguous; therefore, ISDs
that use it SHOULD state a definition for it.
$ daemon
(I) A computer program that is not invoked explicitly but waits
until a specified condition occurs, and then runs with no
associated user (principal), usually for an administrative
purpose. (See: zombie.)
$ dangling threat
(N) A threat to a system for which there is no corresponding
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vulnerability and, therefore, no implied risk. [C4009]
$ dangling vulnerability
(N) A vulnerability of a system for which there is no
corresponding threat and, therefore, no implied risk. [C4009]
$ DASS
(I) See: Distributed Authentication Security Service.
$ data
(I) Information in a specific representation, usually as a
sequence of symbols that have meaning and especially a
representation that can be processed or produced by a computer.
$ Data Authentication Algorithm, data authentication algorithm
(N) /capitalized/ The ANSI standard for a keyed hash function that
is equivalent to DES cipher block chaining with IV = 0. [A9009]
(D) /not capitalized/ Synonym for "checksum".
Deprecated Term: ISDs SHOULD NOT use the uncapitalized form, "data
authentication algorithm", as a synonym for other kinds of
checksums.
$ Data Authentication Code, data authentication code
1. (N) /capitalized/ A specific U.S. Government standard [FP113]
for a checksum that is computed by the Data Authentication
Algorithm. (Also known as the ANSI standard Message Authentication
Code [A9009].) (See: DAC.)
2. (D) /not capitalized/ Synonym for checksum.
Deprecated Term: ISDs SHOULD NOT use "data authentication code" as
a synonym for other kinds of checksums; that usage would mix
concepts in a potentially misleading way (see: authentication
code). Instead, use "checksum", "error detection code", "hash",
"keyed hash", "Message Authentication Code", or "protected
checksum", depending on what is meant.
$ data compromise
(I) A security incident in which information is exposed to
potential unauthorized access, such that unauthorized disclosure,
alteration, or use of the information may have occurred. (Compare:
security compromise.)
(O) A "compromise" is "A communication or physical transfer of
information to an unauthorized recipient." [DoD5]
$ data confidentiality
(I) The property that data is not disclosed to system entities
unless they have been authorized to know the data. (See: Bell-
LaPadula model, classification, data confidentiality service.
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Compare: privacy.)
(D) "The property that information is not made available or
disclosed to unauthorized individuals, entities, or processes
[i.e., to any unauthorized system entity]." [I7498 Part 2].
Deprecated Definition: The phrase "made available" might be
interpreted to mean that the data could be altered, and that would
confuse this term with the concept of "data integrity".
$ data confidentiality service
(I) A security service that protects data against unauthorized
disclosure. (See: access control, data confidentiality, flow
control, inference control.)
Deprecated Definition: ISDs SHOULD NOT use this term as a synonym
for "privacy", which is a different concept.
$ Data Encryption Algorithm (DEA)
(N) A symmetric block cipher, defined in the U.S. Government's
DES. DEA uses a 64-bit key, of which 56 bits are independently
chosen and 8 are parity bits, and maps a 64-bit block into another
64-bit block. [FP046] (See: AES, symmetric cryptography.)
Usage: This algorithm is usually referred to as "DES". The
algorithm has also been adopted in standards outside the
Government (e.g., [A3092]).
$ data encryption key (DEK)
(I) A cryptographic key that is used to encipher application data.
(Compare: key-encrypting key.)
$ Data Encryption Standard (DES)
(N) A U.S. Government standard [FP046] that specifies the DEA and
states policy for using the algorithm to protect unclassified,
sensitive data. (See: AES.)
$ data integrity
1. (I) The property that data has not been changed, destroyed, or
lost in an unauthorized or accidental manner. (See: Biba model,
data integrity service.)
2. (O) "The property that information has not been modified or
destroyed in an unauthorized manner." [I7498 Part 2]
Usage: Deals with (a) constancy of and confidence in data values,
and not with either (b) information that the values represent
(see: correctness integrity) or (c) the trustworthiness of the
source of the values (see: source integrity).
$ data integrity service
(I) A security service that protects against unauthorized changes
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to data, including both intentional change or destruction and
accidental change or loss, by ensuring that changes to data are
detectable. (See: data integrity.)
Tutorial: A data integrity service can only detect a change and
report it to an appropriate system entity; changes cannot be
prevented unless the system is perfect (error-free) and no
malicious user has access. However, a system that offers data
integrity service might also attempt to correct and recover from
changes.
Relationship between data integrity service and authentication
services: Although data integrity service is defined separately
from data origin authentication service and peer entity
authentication service, it is closely related to them.
Authentication services depend, by definition, on companion data
integrity services. Data origin authentication service provides
verification that the identity of the original source of a
received data unit is as claimed; there can be no such
verification if the data unit has been altered. Peer entity
authentication service provides verification that the identity of
a peer entity in a current association is as claimed; there can be
no such verification if the claimed identity has been altered.
$ data origin authentication
(I) "The corroboration that the source of data received is as
claimed." [I7498 Part 2] (See: authentication.)
$ data origin authentication service
(I) A security service that verifies the identity of a system
entity that is claimed to be the original source of received data.
(See: authentication, authentication service.)
Tutorial: This service is provided to any system entity that
receives or holds the data. Unlike peer entity authentication
service, this service is independent of any association between
the originator and the recipient, and the data in question may
have originated at any time in the past.
A digital signature mechanism can be used to provide this service,
because someone who does not know the private key cannot forge the
correct signature. However, by using the signer's public key,
anyone can verify the origin of correctly signed data.
This service is usually bundled with connectionless data integrity
service. (See: ("relationship between data integrity service and
authentication services" under) data integrity service.
$ data owner
(O) /U.S. Government/ The organization that has the final
statutory and operational authority for specified information.
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$ data privacy
(D) Synonym for "data confidentiality".
Deprecated Term: ISDs SHOULD NOT use this term; it mixes concepts
in a potentially misleading way. Instead, use either "data
confidentiality" or "privacy" or both, depending on what is meant.
$ data recovery
1. (I) /cryptanalysis/ A process for learning, from some cipher
text, the plain text that was previously encrypted to produce the
cipher text. (See: recovery.)
2. (I) /system integrity/ The process of restoring information
following damage or destruction.
$ data security
(I) The protection of data from disclosure, alteration,
destruction, or loss that either is accidental or is intentional
but unauthorized.
Tutorial: Both data confidentiality service and data integrity
service are needed to achieve data security.
$ datagram
(I) "A self-contained, independent entity of data [i.e., a data
object, a discrete set of bits] carrying sufficient information to
be routed from the source to the destination." [R1983]
$ DEA
(N) See: Data Encryption Algorithm.
$ deception
(I) A circumstance or event that may result in an authorized
entity receiving false data and believing it to be true. (See:
authentication.)
Tutorial: This is a type of threat consequence, and it can be
caused by the following types of threat actions: masquerade,
falsification, and repudiation.
$ decipher
(D) Synonym for "decrypt".
Deprecated Definition: ISDs SHOULD NOT use this term as a synonym
for "decrypt". However, see usage note under "encryption".
$ decipherment
(D) Synonym for "decryption".
Deprecated Definition: ISDs SHOULD NOT use this term as a synonym
for "decryption". However, see the usage note under "encryption".
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$ decode
1. (I) Convert encoded data back to its original form of
representation. (Compare: decrypt.)
2. (D) Synonym for "decrypt".
Deprecated Definition: Encoding is not usually meant to conceal
meaning. Therefore, ISDs SHOULD NOT use this term as a synonym for
"decrypt", because that would mix concepts in a potentially
misleading way.
$ decrypt
(I) Cryptographically restore cipher text to the plaintext form it
had before encryption.
$ decryption
(I) See: (secondary definition under) encryption.
$ dedicated security mode
(I) A mode of operation of an information system, wherein all
users have the clearance or authorization, and the need-to-know,
for all data handled by the system. In this mode, the system may
handle either (a) a single classification level or category of
information or (b) a range of levels and categories. [DoD2]
Usage: This mode was defined in U.S. DoD policy on system
accreditation, but the term is also used outside the Government.
$ default account
(I) A system login account (usually accessed with a user
identifier and password) that has been predefined in a
manufactured system to permit initial access when the system is
first put into service.
Tutorial: Sometimes, the default user name and password are the
same in each copy of the system. In any case, when the system is
put into service, the default password should immediately be
changed or the default account should be disabled.
$ defense in depth
(I) An approach to constructing security architectures that uses
layered and complementary security mechanisms and countermeasures,
so that if one security mechanism is defeated, one or more other
mechanisms (which are "behind" or "beneath" the first mechanism)
still provide protection.
Tutorial: This concept is appealing because it aligns with
traditional warfare doctrine, which applies defense in depth to
physical, geospatial structures. It is more difficult to apply the
concept to logical, cyberspace structures of computer networks.
The concept assumes that networks have a spatial or topological
representation. It also assumes that there can be implemented --
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from the "outer perimeter" of a network, through its various
"layers" of components, to its "center" (i.e., to the subscriber
application systems supported by the network) -- a varied series
of countermeasures that together provide adequate protection.
However, it is more difficult to map the topology of networks and
make certain that no paths exist by which an attacker could bypass
defensive layers.
$ Defense Information Infrastructure (DII)
(O) /U.S. DoD/ The U.S. DoD's shared or interconnected system of
computers, communications, data, applications, security, people,
training, and other support structure, serving local and worldwide
information needs. (See: DISN.)
Tutorial: The DII connects U.S. DoD mission support, command and
control, and intelligence computers and users through voice, data,
imagery, video, and multimedia services, and provides information
processing and value-added services to subscribers over the DISN.
Users' own data and application software are not considered part
of the DII.
$ Defense Information Systems Network (DISN)
(O) /U.S. DoD/ The U.S. DoD's consolidated, worldwide, enterprise
level telecommunications infrastructure that provides end-to-end
information transfer for supporting military operations; a part of
the DII.
$ degauss
1a. (N) Apply a magnetic field to permanently remove, erase, or
clear data from a magnetic storage medium, such as a tape or disk
[NCS25].
1b. (N) Reduce magnetic flux density to zero by applying a
reversing magnetic field. (See: magnetic remanence.)
$ degausser
(N) An electrical device that can degauss magnetic storage media.
$ DEK
(I) See: data encryption key.
$ delta CRL
(I) A partial CRL that only contains entries for X.509
certificates that have been revoked since the issuance of a prior,
base CRL. This method can be used to partition CRLs that become
too large and unwieldy. (Compare: CRL distribution point.)
$ demilitarized zone (DMZ)
(D) Synonym for "buffer zone".
Deprecated Term: ISDs SHOULD NOT use this term with this
definition; that would mix concepts in a potentially misleading
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way. (See: (Deprecated Usage under) Green Book.)
$ denial of service
(I) The prevention of authorized access to a system resource or
the delaying of system operations and functions. (See:
availability, critical, flooding.)
Tutorial: A denial-of-service attack can prevent the normal
conduct of business on the Internet. There are four types of
solutions to this security problem:
- Awareness: Maintaining cognizance of security threats and
vulnerabilities. (See: CERT.)
- Detection: Finding attacks on end systems and subnetworks.
(See: intrusion detection.)
- Prevention: Following defensive practices on network-connected
systems. (See: [RFC 2167].)
- Response: Reacting effectively when attacks occur. (See: CSIRT,
contingency plan.)
$ DES
(N) See: Data Encryption Standard.
$ designated approving authority (DAA)
(O) /U.S. Government/ Synonym for "accreditor".
$ dictionary attack
(I) An attack that uses a brute-force technique of successively
trying all the words in some large, exhaustive list.
Examples: An attack on an authentication service by trying all
possible passwords. An attack on encryption by encrypting some
known plaintext phrase with all possible keys so that the key for
any given encrypted message containing that phrase may be obtained
by lookup.
$ Diffie-Hellman
(N) A key-agreement algorithm published in 1976 by Whitfield
Diffie and Martin Hellman [DH76, R2631].
Tutorial: Diffie-Hellman does key establishment, not encryption.
However, the key that it produces may be used for encryption, for
further key management operations, or for any other cryptography.
The algorithm is described in [R2631] and [Schn]. In brief, Alice
and Bob together pick large integers that satisfy certain
mathematical conditions, and then use the integers to each
separately compute a public-private key pair. They send each other
their public key. Each person uses their own private key and the
other person's public key to compute a key, k, that, because of
the mathematics of the algorithm, is the same for each of them.
Passive wiretapping cannot learn the shared k, because k is not
transmitted, and neither are the private keys needed to compute k.
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The difficulty of breaking Diffie-Hellman is considered to be
equal to the difficulty of computing discrete logarithms modulo a
large prime. However, without additional mechanisms to
authenticate each party to the other, a protocol based on the
algorithm may be vulnerable to a man-in-the-middle attack.
$ digest
See: message digest.
$ digital certificate
(I) A certificate document in the form of a digital data object (a
data object used by a computer) to which is appended a computed
digital signature value that depends on the data object. (See:
attribute certificate, capability, public-key certificate.)
Deprecated Usage: ISDs SHOULD NOT use this term to refer to a
signed CRL or CKL. Although the recommended definition can be
interpreted to include other signed items, the security community
does not use the term with those meanings.
$ digital certification
(D) Synonym for "certification".
Deprecated Definition: ISDs SHOULD NOT use this definition unless
the context is not sufficient to distinguish between digital
certification and another kind of certification, in which case it
would be better to use "public-key certification" or another
phrase that indicates what is being certified.
$ digital document
(I) An electronic data object that represents information
originally written in a non-electronic, non-magnetic medium
(usually ink on paper) or is an analogue of a document of that
type.
$ digital envelope
(I) A combination of (a) encrypted content data (of any kind)
intended for a recipient and (b) the content encryption key in an
encrypted form that has been prepared for the use of the
recipient.
Usage: In ISDs, the term should be defined at the point of first
use because, although the term is defined in PKCS #7 and used in
S/MIME, it is not widely known.
Tutorial: Digital enveloping is not simply a synonym for
implementing data confidentiality with encryption; digital
enveloping is a hybrid encryption scheme to "seal" a message or
other data, by encrypting the data and sending both it and a
protected form of the key to the intended recipient, so that no
one other than the intended recipient can "open" the message. In
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PCKS #7, it means first encrypting the data using a symmetric
encryption algorithm and a secret key, and then encrypting the
secret key using an asymmetric encryption algorithm and the public
key of the intended recipient. In S/MIME, additional methods are
defined for encrypting the content encryption key.
$ Digital ID(service mark)
Deprecated Term: ISDs SHOULD NOT use this term as a synonym for
"digital certificate". The term (a) is the service mark of a
commercial firm and (b) unnecessarily duplicates the meaning of
other, well-established terms. (See: credential.)
$ digital key
Usage: The adjective "digital" need not be used with "key" or
"cryptographic key", unless the context is insufficient to
distinguish the digital key from another kind of key, such as a
metal key for a door lock.
$ digital notary
(I) An electronic functionary analogous to a notary public.
Provides a trusted time stamp for a digital document, so that
someone can later prove that the document existed at that point in
time; verifies the signature(s) on a signed document before
applying the stamp. (See: notarization.)
$ digital signature
1. (I) A value computed with a cryptographic algorithm and
appended to a data object in such a way that any recipient of the
data can use the signature to verify the data's origin and
integrity. (See: data origin authentication service, data
integrity service, signer. Compare: digitized signature,
electronic signature.)
2. (I) "Data appended to, or a cryptographic transformation of, a
data unit that allows a recipient of the data unit to prove the
source and integrity of the data unit and protect against forgery,
e.g. by the recipient." [I7498 Part 2]
Tutorial: A digital signature should have these properties:
- Uniquely identify a system entity as being the signer.
- Be under the signer's sole control, so that it cannot be
created by any other entity.
- Be capable of being verified. (See: validate vs. verify.)
- Be bound to the signed data object in such a way that if the
data is changed, then when an attempt is made to verify the
signature, it will be seen as not authentic.
To achieve these properties, the data object is first input to a
hash function, and then the hash result is cryptographically
transformed using a private key of the signer. The final resulting
value is called the digital signature of the data object. The
signature value is a protected checksum, because the properties of
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a cryptographic hash ensure that if the data object is changed,
the digital signature will no longer match it. The digital
signature is unforgeable because one cannot be certain of
correctly creating or changing the signature without knowing the
private key of the supposed signer.
Some digital signature schemes use a asymmetric encryption
algorithm (e.g., see: RSA) to transform the hash result. Thus,
when Alice needs to sign a message to send to Bob, she can use her
private key to encrypt the hash result. Bob receives both the
message and the digital signature. Bob can use Alice's public key
to decrypt the signature, and then compare the plaintext result to
the hash result that he computes by hashing the message himself.
If the values are equal, Bob accepts the message because he is
certain that it is from Alice and has arrived unchanged. If the
values are not equal, Bob rejects the message because either the
message or the signature was altered in transit.
Other digital signature schemes (e.g., see: DSS) transform the
hash result with an algorithm (e.g., see: DSA, El Gamal) that
cannot be directly used to encrypt data. Such a scheme creates a
signature value from the hash and provides a way to verify the
signature value, but does not provide a way to recover the hash
result from the signature value. In some countries, such a scheme
may improve exportability and avoid other legal constraints on
usage. Alice sends the signature value to Bob along with both the
message and its hash result. The algorithm enables Bob to use
Alice's public signature key and the signature value to verify the
hash result he receives. Then, as before, he compares that hash
result she sent to the one that he computes by hashing the message
himself.
$ Digital Signature Algorithm (DSA)
(N) An asymmetric cryptographic algorithm for a digital signature
in the form of a pair of large numbers. The signature is computed
using rules and parameters such that the identity of the signer
and the integrity of the signed data can be verified. (See: DSS.)
$ Digital Signature Standard (DSS)
(N) The U.S. Government standard [FP186] that specifies the DSA.
$ digital watermarking
(I) Computing techniques for inseparably embedding unobtrusive
marks or labels as bits in digital data -- text, graphics, images,
video, or audio -- and for detecting or extracting the marks
later.
Tutorial: The set of embedded bits (the digital watermark) is
sometimes hidden, usually imperceptible, and always intended to be
unobtrusive. Depending on the particular technique that is used,
digital watermarking can assist in proving ownership, controlling
duplication, tracing distribution, ensuring data integrity, and
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performing other functions to protect intellectual property
rights. [ACM]
$ digitized signature
(D) Denotes various forms of digitized images of handwritten
signatures. (Compare: digital signature).
Deprecated Term: ISDs SHOULD NOT use this term; it looks like
sloppy use of "digital signature", which is the term standardized
by [I7498 Part 2]. (See: electronic signature.)
$ DII
(O) See: Defense Information Infrastructure.
$ directory, Directory
1. (I) /not capitalized/ Refers generically to a database server
or other system that provides information -- such as a digital
certificate or CRL -- about an entity whose name is known.
(Compare: repository.)
2. (N) /capitalized/ Refers specifically to the X.500 Directory.
(See: DN, X.500.)
$ Directory Access Protocol (DAP)
(N) An OSI protocol [X519] for communication between a Directory
User Agent (a type of X.500 client) and a Directory System Agent
(a type of X.500 server). (See: LDAP.)
$ disaster plan
(O) Synonym for "contingency plan".
Deprecated Term: ISDs SHOULD NOT use this term; instead, for
consistency and neutrality of language, ISDs SHOULD use
"contingency plan".
$ disclosure
See: unauthorized disclosure. Compare: exposure.
$ discretionary access control
1a. (I) An access control service that enforces a security policy
based on the identity of system entities and the authorizations
associated with those identities. (See: access control list, DAC,
identity-based security policy, mandatory access control.)
Derivation: This service is termed "discretionary" because an
entity can be granted access rights to a resource such that the
entity can by its own volition enable other entities to access the
resource. That is, the service can incorporate a concept of
ownership in which access rights can be granted and revoked by the
user that owns the resource.
1b. (O) /formal model/ "A means of restricting access to objects
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based on the identity of subjects and/or groups to which they
belong. The controls are discretionary in the sense that a subject
with a certain access permission is capable of passing that
permission (perhaps indirectly) on to any other subject." [DoD1]
$ DISN
(O) See: Defense Information Systems Network (DISN).
$ disruption
(I) A circumstance or event that interrupts or prevents the
correct operation of system services and functions. (See:
availability, critical, system integrity.)
Tutorial: Disruption is a type of threat consequence; it can be
caused by the following types of threat actions: incapacitation,
corruption, and obstruction.
$ Distinguished Encoding Rules (DER)
(N) A subset of the Basic Encoding Rules, which gives exactly one
way to represent any ASN.1 value as an octet string [X690].
Tutorial: There usually is more than one way to encode ASN.1 in
BER. Therefore, DER is used in applications in which a unique
encoding is needed, such as when a digital signature is computed
on an ASN.1 value.
$ distinguished name (DN)
(N) An identifier that uniquely represents an object in the X.500
Directory Information Tree (DIT) [X501]. (Compare: domain name,
identity.)
Tutorial: A DN is a set of attribute values that identify the path
leading from the base of the DIT to the object that is named. An
X.509 public-key certificate or CRL contains a DN that identifies
its issuer, and an X.509 attribute certificate contains a DN or
other form of name that identifies its subject.
$ distributed attack
1a. (I) An attack that is implemented with distributed computing.
(See: zombie.)
1b. (I) An attack that deploys multiple threat agents.
$ Distributed Authentication Security Service (DASS)
(I) An experimental Internet protocol [R1507] that uses
cryptographic mechanisms to provide strong, mutual authentication
services in a distributed environment.
$ distributed computing
(I) A technique that disperses a single, logically related set of
tasks among a group of geographically separate yet cooperating
computers. (See: distributed attack.)
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$ distribution point
(I) An X.500 Directory entry or other information source that is
named in a v3 X.509 public-key certificate extension as a location
from which to obtain a CRL that may list the certificate.
Tutorial: A v3 X.509 public-key certificate may have a
"cRLDistributionPoints" extension that names places to get CRLs on
which the certificate might be listed. (See: certificate profile.)
A CRL obtained from a distribution point may (a) cover either all
reasons for which a certificate might be revoked or only some of
the reasons, (b) be issued by either the authority that signed the
certificate or some other authority, and (c) contain revocation
entries for only a subset of the full set of certificates issued
by one CA or (d) contain revocation entries for multiple CAs.
$ DMZ
(D) See: demilitarized zone.
$ DN
(N) See: distinguished name.
$ DNS
(I) See: Domain Name System.
$ doctrine
See: security doctrine.
$ DoD
(N) Department of Defense.
Usage: To ensure international understanding, ISDs should use this
abbreviation only with a national qualifier (e.g., U.S. DoD).
$ DOI
(I) See: Domain of Interpretation.
$ domain
1a. (I) /general security/ An environment or context that is
defined by a security policy, security model, or security
architecture to include a set of system resources and a set of
system entities that have the right to access the resources. (See:
domain of interpretation, security perimeter. Compare: COI,
enclave.)
Tutorial: A "controlled interface" or "guard" is required to
transfer information between network domains that operate under
different security policies.
1b. (O) /security policy/ A set of users, their information
objects, and a common security policy. [DGSA, SP33]
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2. (N) /computer security/ A operating state or mode of a set of
computer hardware.
Tutorial: Most computers have at least two hardware operating
modes [Gass]:
- "Privileged" mode: Also called "executive", "master", "system",
kernel", or "supervisor" mode. In this mode, software can
execute any machine instruction and access any machine storage.
- "Unprivileged" mode: Also called "user", "application", or
"problem" mode. In this mode, software is restricted to a
subset of the instructions and a subset of the storage.
3. (I) /Internet/ That part of the Internet domain name space tree
(RFC 1034) that is at or below the name that specifies the domain.
A domain is a subdomain of another domain if it is contained
within that domain. For example, D.C.B.A is a subdomain of C.B.A.
(See: Domain Name System.)
4. (O) /MISSI/ The domain of a MISSI CA is the set of MISSI users
whose certificates are signed by the CA.
5. (O) /OSI/ An administrative partition of a complex distributed
OSI system.
6. (O) "A distinct scope within which certain common
characteristics are exhibited and common rules are observed."
[CORBA]
$ domain name
(I) The style of identifier -- a sequence of case-insensitive
ASCII labels separated by dots (e.g., "bbn.com") -- defined for
subtrees in the Internet DNS and used in other Internet
identifiers, like host names (e.g., "rosslyn.bbn.com"), mailbox
names (e.g., "rshirey@bbn.com."), and URLs (e.g.,
"http://www.rosslyn.bbn.com./foo"). (See: DN, domain.)
Tutorial: The name space of the DNS (RFC 1591) is a tree structure
in which each node and leaf holds records describing a resource.
Each node has a label. The domain name of a node is the list of
labels on the path from the node to the root of the tree. The
labels in a domain name are printed or read left to right, from
the most specific (lowest, farthest from the root) to the least
specific (highest, closest to the root), but the root's label is
the null string. (See: country code.)
$ Domain Name System (DNS)
(I) The main Internet operations database, which is distributed
over a collection of servers and used by client software for
purposes such as translating a domain name-style host name into an
IP address (e.g., "rosslyn.bbn.com" is "192.1.7.10") and locating
a host that accepts mail for some mailbox address. [R1034]
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Tutorial: The DNS has three major components: (a) Domain name
space and resource records: Specifications for the tree-structured
domain name space, and data associated with the names. (b) Name
servers: Programs that hold information about a subset of the
tree's structure and data holdings, and also hold pointers to
other name servers that can provide information from any part of
the tree. (c) Resolvers: Programs that extract information from
name servers in response to client requests; typically, system
routines directly accessible to user programs.
Extensions to the DNS [R2065, R2137, R2536] support (a) key
distribution for public keys needed for the DNS and for other
protocols, (b) data origin authentication service and data
integrity service for resource records, (c) data origin
authentication service for transactions between resolvers and
servers, and (d) access control of records.
$ domain of interpretation (DOI)
(I) /IPsec/ An ISAKMP/IKE DOI defines payload formats, exchange
types, and conventions for naming security-relevant information
such as security policies or cryptographic algorithms and modes.
Example: See [R2407].
Derivation: The DOI concept is based on work by the TSIG's CIPSO
Working Group.
$ dominate
(I) Security level A is said to "dominate" security level B if the
hierarchical classification level of A is greater (higher) than or
equal to that of B and the nonhierarchical categories of A include
all of those of B. (See: lattice, lattice model.)
$ dongle
(I) A portable, physical, usually electronic device that is
required to be attached to a computer to enable a particular
software program to run. (See: token.)
Tutorial: A dongle is essentially a physical key used for copy
protection of software, because the program will not run unless
the matching dongle is attached. When the software runs, it
periodically queries the dongle and quits if the dongle does not
reply with the proper authentication information. Dongles were
originally constructed as an EPROM (erasable programmable read-
only memory) to be connected to a serial input-output port of a
personal computer.
$ downgrade
(I) /data security/ Reduce the classification level of data
without changing the information content of the data. (Compare:
upgrade. See: regrade.)
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$ draft RFC
Deprecated Term: ISDs SHOULD NOT use this term; the Request for
Comment series is archival in nature and does not have a "draft"
category. (See: Internet Draft, (Draft Standard under) Internet
Standard).)
$ Draft Standard
(I) See: (secondary definition under) Internet Standard.
$ DSA
(N) See: Digital Signature Algorithm.
$ DSS
(N) See: Digital Signature Standard.
$ dual control
(I) A procedure that uses two or more entities (usually persons)
operating in concert to protect a system resource, such that no
single entity acting alone can access that resource. (See: no-lone
zone, separation of duties, split knowledge.)
$ dual signature
(O) /SET/ A single digital signature that protects two separate
messages by including the hash results for both sets in a single
encrypted value. [SET2]
Deprecated Term: ISDs SHOULD NOT use this term except when
qualified as "SET(trademark) dual signature" with this definition.
Tutorial: Generated by hashing each message separately,
concatenating the two hash results, and then hashing that value
and encrypting the result with the signer's private key. Done to
reduce the number of encryption operations and to enable
verification of data integrity without complete disclosure of the
data.
$ dual-use certificate
(I) A certificate that is intended for use with both digital
signature and data encryption services. [SP32]
Usage: An ISD that uses the term SHOULD state a definition by
identifying the intended uses of the certificate, because there
are more than just these two. A v3 X.509 public-key certificate
may have a "key Usage" extension, which indicates the purposes for
which the public key may be used. (See: certificate profile.)
$ duty
(I) An attribute of a role that obligates an entity playing the
role to perform one or more tasks, which usually are essential for
the functioning of the system. [Sand] (Compare authorization,
privilege. See: role, billet.)
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$ e-cash
(D) Electronic cash; money that is in the form of data and can be
used as a payment mechanism on the Internet.
Deprecated Usage: Many different types of electronic cash have
been devised, using a variety of security mechanisms; therefore,
ISDs that use the term SHOULD state a definition for it.
$ EAP
(I) See: Extensible Authentication Protocol.
$ EAL
(O) See: evaluation assurance level.
$ Easter egg
(D) "Hidden functionality within an application program, which
becomes activated when an undocumented, and often convoluted, set
of commands and keystrokes is entered. Easter eggs are typically
used to display the credits for the development team and [are]
intended to be non-threatening" [SP28], but Easter eggs have the
potential to contain malicious code.
Deprecated Usage: It is likely that other cultures have different
metaphors for this concept. Therefore, to ensure international
understanding, ISDs SHOULD NOT use this term. (See: (Deprecated
Usage under) Green Book.)
$ eavesdropping
(I) Passive wiretapping done secretly, i.e., without the knowledge
of the originator or the intended recipients of the communication.
$ ECB
(N) See: electronic codebook.
$ ECDSA
(N) See: Elliptic Curve Digital Signature Algorithm.
$ economy of alternatives
(I) The principle that a security mechanism should be designed to
minimize the number of alternative ways of achieving a service.
(Compare: economy of mechanism.)
$ economy of mechanism
(I) The principle that a security mechanism should be designed to
be as simple as possible, so that (a) the mechanism can be
correctly implemented and (b) it can be verified that the
operation of the mechanism enforces the system's security policy.
(Compare: economy of alternatives, least privilege.)
$ ECU
(N) See: end cryptographic unit.
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$ EDI
(I) See: electronic data interchange.
$ EDIFACT
(N) See: (secondary definition under) electronic data interchange.
$ EE
Deprecated Term: ISDs SHOULD NOT use this abbreviation; there
could be confusion among "end entity", "end-to-end encryption",
"escrowed encryption standard", and other terms.
$ EES
(O) See: Escrowed Encryption Standard.
$ effective key length
(O) "A measure of strength of a cryptographic algorithm,
regardless of actual key length." [IATF]
$ effectiveness
(O) /ITSEC/ A property of a TOE representing how well it provides
security in the context of its actual or proposed operational use.
$ El Gamal algorithm
(N) An algorithm for asymmetric cryptography, invented in 1985 by
Taher El Gamal, that is based on the difficulty of calculating
discrete logarithms and can be used for both encryption and
digital signatures.
$ electronic codebook (ECB)
(N) An block cipher mode in which a plaintext block is used
directly as input to the encryption algorithm and the resultant
output block is used directly as cipher text [FP081].
$ electronic commerce
1. (I) Business conducted through paperless exchanges of
information, using electronic data interchange, electronic funds
transfer (EFT), electronic mail, computer bulletin boards,
facsimile, and other paperless technologies.
2. (O) /SET/ "The exchange of goods and services for payment
between the cardholder and merchant when some or all of the
transaction is performed via electronic communication." [SET2]
$ electronic data interchange (EDI)
(I) Computer-to-computer exchange, between trading partners, of
business data in standardized document formats.
Tutorial: EDI formats have been standardized primarily by ANSI X12
and by EDIFACT (EDI for Administration, Commerce, and
Transportation), which is an international, UN-sponsored standard
primarily used in Europe and Asia. X12 and EDIFACT are aligning to
create a single, global EDI standard.
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$ Electronic Key Management System (EKMS)
(O) "Interoperable collection of systems developed by ... the U.S.
Government to automate the planning, ordering, generating,
distributing, storing, filling, using, and destroying of
electronic keying material and the management of other types of
COMSEC material." [C4009]
$ electronic signature
Deprecated Term: ISDs SHOULD NOT use this term; there is no
current consensus on its definition. Instead, use "digital
signature", if that is what was intended. (See: digitized
signature.)
$ electronic wallet
Deprecated Term: ISDs SHOULD NOT use this term; there is no
current consensus on its definition. Meanings range from "digital
certificate" to "smartcard", and some uses and definitions may be
proprietary. (See: (Deprecated Usage under) Green Book.)
$ elliptic curve cryptography (ECC)
(I) A type of asymmetric cryptography based on mathematics of
groups that are defined by the points on a curve, where the curve
is defined by a quadratic equation in a finite field. [Schn]
Tutorial: The most efficient implementation of ECC is claimed to
be stronger per bit of key (against cryptanalysis that uses a
brute force attack) than any other known form of asymmetric
cryptography. ECC is based on mathematics different than the kinds
originally used to define the Diffie-Hellman algorithm and the
Digital Signature Algorithm, but ECC can be used to define an
algorithm for key agreement that is an analog of Diffie-Hellman
[A9063] and an algorithm for digital signature that is an analog
of DSA [A9062]. (See: ECDSA.)
$ Elliptic Curve Digital Signature Algorithm (ECDSA)
(N) A standard [A9062] that is the analog, in elliptic curve
cryptography, of the Digital Signature Algorithm.
$ emanation
(I) An signal (e.g., electromagnetic or acoustic) that is emitted
by a system (e.g., through radiation or conductance) as a
consequence (i.e., byproduct) of the system's operation, and that
may contain information. (See: emanations security.)
$ emanations security (EMSEC)
(I) Physical security measures to protect against data compromise
that could occur because of emanations that might be received and
read by an unauthorized party. (See: TEMPEST.)
Usage: Refers both to preventing or limiting emanations from a
system and to preventing or limiting the ability of unauthorized
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parties to receive the emissions.
$ embedded cryptography
(N) "Cryptography engineered into an equipment or system whose
basic function is not cryptographic." [C4009]
$ emergency plan
(D) Synonym for "contingency plan".
Deprecated Term: ISDs SHOULD NOT use this term. Instead, for
neutrality and consistency of language, use "contingency plan".
$ emergency response
(O) An urgent response to a fire, flood, civil commotion, natural
disaster, bomb threat, or other serious situation, with the intent
of protecting lives, limiting damage to property, and minimizing
disruption of system operations. [FP087] (See: availability,
CERT.)
$ EMSEC
(I) See: emanations security.
$ EMV
(N) An abbreviation of "Europay, MasterCard, Visa". Refers to a
specification for smart cards that are used as payment cards, and
for related terminals and applications. [EMV1, EMV2, EMV3]
$ Encapsulating Security Payload (ESP)
(I) An Internet protocol [R2406] designed to provide data
confidentiality service and other security services for IP
datagrams. (See: IPsec. Compare: AH.)
Tutorial: ESP may be used alone, or in combination with AH, or in
a nested fashion with tunneling. Security services can be provided
between a pair of communicating hosts, between a pair of
communicating security gateways, or between a host and a gateway.
The ESP header is encapsulated by the IP header, and the ESP
header encapsulates either the upper layer protocol header
(transport mode) or an IP header (tunnel mode). ESP can provide
data confidentiality service, data origin authentication service,
connectionless data integrity service, an anti-replay service, and
limited traffic-flow confidentiality. The set of services depends
on the placement of the implementation and on options selected
when the security association is established.
$ encipher
(D) Synonym for "encrypt".
Deprecated Definition: ISDs SHOULD NOT use this term as a synonym
for "encrypt". However, see usage note under "encryption".
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$ encipherment
(D) Synonym for "encryption".
Deprecated Definition: ISDs SHOULD NOT use this term as a synonym
for "encryption". However, see usage note under "encryption".
$ enclave
1. (I) A set of system resources that operate in the same security
domain and that share the protection of a common, continuous
security perimeter. (Compare: domain.)
2. (O) /U.S. Government/ "Collection of computing environments
connected by one or more internal networks under the control of a
single authority and security policy, including personnel and
physical security." [C4009]
$ encode
1. (I) Use a system of symbols to represent information, which
might originally have some other representation. Example: Morse
code. (See: ASCII, BER.) (See: code, decode.)
2. (D) Synonym for "encrypt".
Deprecated Definition: ISDs SHOULD NOT use this term as a synonym
for "encrypt"; encoding is not always meant to conceal meaning.
$ encrypt
(I) Cryptographically transform data to produce cipher text. (See:
encryption. Compare: seal.)
$ encryption
1. (I) Cryptographic transformation of data (called "plain text")
into a form (called "cipher text") that conceals the data's
original meaning to prevent it from being known or used. If the
transformation is reversible, the corresponding reversal process
is called "decryption", which is a transformation that restores
encrypted data to its original state. (See: cryptography.)
2. (O) "The cryptographic transformation of data to produce
ciphertext." [I7498 Part 2]
Usage: For this concept, ISDs SHOULD use the verb "to encrypt"
(and related variations: encryption, decrypt, and decryption).
However, because of cultural biases involving human burial, some
international documents (particularly ISO and CCITT standards)
avoid "to encrypt" and instead use the verb "to encipher" (and
related variations: encipherment, decipher, decipherment).
Tutorial: Usually, the plaintext input to an encryption operation
is clear text. But in some cases, the plain text may be cipher
text that was output from another encryption operation. (See:
superencryption.)
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Encryption and decryption involve a mathematical algorithm for
transforming data. In addition to the data to be transformed, the
algorithm has one or more inputs that are control parameters: (a)
a key that varies the transformation and, in some cases, (b) an IV
that establishes the starting state of the algorithm.
$ encryption certificate
(I) A public-key certificate that contains a public key that is
intended to be used for decrypting data, rather than for verifying
digital signatures or performing other cryptographic functions.
Tutorial: A v3 X.509 public-key certificate may have a "keyUsage"
extension that indicates the purpose for which the certified
public key is intended. (See: certificate profile.)
$ end cryptographic unit (ECU)
1. (N) Final destination device into which a key is loaded for
operational use.
2. (N) A device that (a) performs cryptographic functions, (b)
typically is part of a larger system for which the device provides
security services, and (c), from the viewpoint of a supporting
security infrastructure such as a key management system, is the
lowest level of identifiable component with which a management
transaction can be conducted
$ end entity
1. (I) A system entity that is the subject of a public-key
certificate and that is using, or is permitted and able to use,
the matching private key only for purposes other than signing a
digital certificate; i.e., an entity that is not a CA.
2. (O) "A certificate subject which uses its public [sic] key for
purposes other than signing certificates." [X509]
Deprecated Definition: ISDs SHOULD NOT use the X.509 definition,
which is misleading and incomplete. First, that definition should
have said "private key" rather than "public key" because
certificates are not usefully signed with a public key. Second,
the X.509 definition is ambiguous regarding whether an end entity
may or may not use the private key to sign a certificate, i.e.,
whether the subject may be a CA. The intent of X.509's authors was
that an end entity certificate is not valid for use in verifying a
signature on an X.509 certificate or X.509 CRL. Thus, it would
have been better for the X.509 definition to have said "only for
purposes other than signing certificates".
Usage: Despite the problems in the X.509 definition, the term
itself is useful in describing applications of asymmetric
cryptography. The way the term is used in X.509 implies that it
was meant to be defined, as we have done here, relative to roles
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that an entity (which is associated with an OSI end system) is
playing or is permitted to play in applications of asymmetric
cryptography other than the PKI that supports applications.
Tutorial: Whether a subject can play both CA and non-CA roles,
with either the same or different certificates, is a matter of
policy. (See: CPS.) A v3 X.509 public-key certificate may have a
"basicConstraints" extension containing a "cA" value that
specifically "indicates whether or not the public key may be used
to verify certificate signatures". (See: certificate profile.)
$ end system
(N) /OSIRM/ A computer that implements all seven layers of the
OSIRM and may attach to a subnetwork. Usage: In the IPS context, a
end system is called a "host".
$ end-to-end encryption
(I) Continuous protection of data that flows between two points in
a network, effected by encrypting data when it leaves its source,
leaving it encrypted while it passes through any intermediate
computers (such as routers), and decrypting only when the data
arrives at the intended final destination. (See: wiretapping.
Compare: link encryption.)
Examples: BLACKER, CANEWARE, IPLI, IPsec, PLI, SDNS, SILS.
Tutorial: When two points are separated by multiple communication
links that are connected by one or more intermediate relays, end-
to-end encryption enables the source and destination systems to
protect their communications without depending on the intermediate
systems to provide the protection.
$ end user
1. (I) /information system/ A system entity, usually a human
individual, that makes use of system resources, primarily for
application purposes as opposed to system management purposes.
2. (D) /PKI/ Synonym for "end entity".
Deprecated Definition: ISDs SHOULD NOT use "end user" as a synonym
for "end entity", because that would mix concepts in a potentially
misleading way.
$ endorsed-for-unclassified cryptographic item (EUCI)
(O) /U.S. Government/ "Unclassified cryptographic equipment that
embodies a U.S. Government classified cryptographic logic and is
endorsed by NSA for the protection of national security
information." [C4009] (Compare: CCI, type 2 product.)
$ entity
See: system entity.
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$ entrapment
(I) "The deliberate planting of apparent flaws in a system for the
purpose of detecting attempted penetrations or confusing an
intruder about which flaws to exploit." [FP039] (See: honey pot.)
$ entropy
1. (I) An information-theoretic measure (usually stated as a
number of bits) of the amount of uncertainty that an attacker
faces to determine the value of a secret. [SP63] (See: strength.)
Example: If a password is said to contain at least 20 bits of
entropy, that means that it must be as hard to find the password
as to guess an 20-bit random number.
2. (I) An information-theoretic measure (usually stated as a
number of bits) of the amount of information in a message; i.e.,
the minimum number of bits needed to encode all possible meanings
of that message. [Schn] (See: uncertainty.)
$ ephemeral
(I) /adjective/ Refers to a cryptographic key or other parameter
that is short-lived, temporary, or used one time. (See: session
key. Compare: static.)
$ erase
(I) Delete magnetically stored data in such a way that the data is
irretrievable by ordinary means, but might be recovered using
laboratory methods. [C4009] (Compare: purge.)
$ error detection code
(I) A checksum designed to detect, but not correct, accidental
(i.e., unintentional) changes in data.
$ Escrowed Encryption Standard (EES)
(N) A U.S. Government standard [FP185] that specifies use of a
symmetric encryption algorithm (SKIPJACK) and a Law Enforcement
Access Field (LEAF) creation method to implement part of a key
escrow system that provides for decryption of telecommunications
when interception is lawfully authorized.
Tutorial: Both SKIPJACK and the LEAF are intended for use in
equipment used to encrypt and decrypt unclassified, sensitive
telecommunications data.
$ ESP
(I) See: Encapsulating Security Payload.
$ Estelle
(N) A language (ISO 9074-1989) for formal specification of
computer network protocols.
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$ ETSI
(N) See: European Telecommunication Standards Institute.
$ EUCI
(O) See: endorsed-for-unclassified cryptographic item.
$ European Telecommunication Standards Institute (ETSI)
(N) An independent, non-profit organization, based in France, that
is officially recognized by the European Commission and
responsible for standardization of information and communication
technologies within Europe.
Tutorial: ETSI is the custodian of a number of security
algorithms, including encryption algorithms for mobile telephone
systems in Europe.
$ evaluated products list, Evaluated Products List
1. (I) /not capitalized/ A list of information system equipment
items that have been evaluated against, and found to be compliant
with, a particular set of criteria.
2. (N) /capitalized, U.S. Government/ The Evaluated Products List
(http://www.radium.ncsc.mil/tpep/epl/) contains items that have
been evaluated against the TCSEC by the NCSC, or against the
Common Criteria by the NIAP or one of its partner agencies in
another county. This List forms Chapter 4 of NSA's "Information
Systems Security Products and Services Catalogue". [C4009]
$ evaluated system
(I) A system that has been evaluated against security criteria
such as the TCSEC or the Common Criteria.
$ evaluation
(I) Assessment of an information system against defined security
criteria, such as the TCSEC or the Common Criteria. (Compare:
certification.)
$ evaluation assurance level (EAL)
(N) A predefined package of assurance components that represents a
point on the Common Criteria's scale for rating confidence in the
security of information technology products and systems.
Tutorial: The Common Criteria defines a scale of seven,
hierarchically ordered EALs for rating a TOE. From highest to
lowest, they are as follows:
- EAL7. Formally verified design and tested.
- EAL6. Semiformally verified design and tested.
- EAL5. Semiformally designed and tested.
- EAL4. Methodically designed, tested, and reviewed.
- EAL3. Methodically tested and checked.
- EAL2. Structurally tested.
- EAL1. Functionally tested.
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An EAL is a consistent, baseline set of requirements. The increase
in assurance from EAL to EAL is accomplished by substituting
higher assurance components (i.e. criteria of increasing rigor,
scope, or depth) from seven assurance classes: (a) configuration
management, (b) delivery and operation, (c) development, (d)
guidance documents, (e) life cycle support, (f) tests, and (g)
vulnerability assessment.
The EALs were developed with the goal of preserving concepts of
assurance that were adopted from earlier criteria, so that results
of previous evaluations would remain relevant. For example, EALs
levels 2-7 are generally equivalent to the assurance portions of
the TCSEC C2-A1 scale. However, this equivalency should be used
with caution. The levels do not derive assurance in the same
manner, and exact mappings do not exist.
$ expire
(I) See: certificate expiration.
$ exposure
(I) A type of threat action whereby sensitive data is directly
released to an unauthorized entity. (See: unauthorized
disclosure.)
Usage: This type includes the following subtypes:
- "Deliberate Exposure": Intentional release of sensitive data to
an unauthorized entity.
- "Scavenging": Searching through data residue in a system to
gain unauthorized knowledge of sensitive data.
- "Human error": In context of exposure, human action or inaction
that unintentionally results in an entity gaining unauthorized
knowledge of sensitive data.
- "Hardware or software error": In context of exposure, system
failure that unintentionally results in an entity gaining
unauthorized knowledge of sensitive data.
$ Extended Security Option
(I) See: (secondary definition under) IPSO.
$ Extensible Authentication Protocol (EAP)
(I) A extension framework for PPP that supports multiple, optional
authentication mechanisms, including cleartext passwords,
challenge-response, and arbitrary dialog sequences. [R3748]
Tutorial: This protocol is intended for use primarily by a host or
router that connects to a network server via switched circuits or
dial-up lines. EAP typically runs directly over IPS data link
protocols or OSIRM layer 2 protocols, such as PPP or IEEE 802,
without requiring IP.
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$ Extensible Markup Language (XML)
(N) A version of Standard Generalized Markup Language (ISO 8879),
which separately represents both a document's content and its
structure. XML was designed by W3C for use on the World Wide Web.
$ extension
(I) A data item defined for optional inclusion in a v3 X.509
public-key certificate or a v2 X.509 CRL.
Tutorial: The formats defined in X.509 can be extended to provide
methods for associating additional attributes with subjects and
public keys and for managing a certification hierarchy:
- "Certificate extension": X.509 defines standard extensions that
may be included in v3 certificates to provide additional key
and security policy information, subject and issuer attributes,
and certification path constraints.
- "CRL extension": X.509 defines extensions that may be included
in v2 CRLs to provide additional issuer key and name
information, revocation reasons and constraints, and
information about distribution points and delta CRLs.
- "Private extension": Additional extensions, each named by an
OID, can be locally defined as needed by applications or
communities. (See: PKIX private extension, SET private
extensions.)
$ external controls
(I) /computer security/ Refers to administrative security,
personnel security, and physical security. (Compare: internal
controls.)
$ extranet
(I) A computer network that an organization uses for application
data traffic between the organization and its business partners.
(Compare: intranet.)
Tutorial: An extranet can be implemented securely, either on the
Internet or using Internet technology, by constructing the
extranet as a VPN.
$ extraction resistance
(O) Capability of cryptographic equipment to resist efforts to
extract keying material directly from the equipment (as opposed to
gaining knowledge of keying material by cryptanalysis). [C4009]
$ fail safe
(I) A mode of system termination that automatically leaves system
processes and components in a secure state when a failure occurs
or is detected in the system.
$ fail soft
(I) Selective termination of affected non-essential system
functions and processes when a failure occurs or is detected in
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the system.
$ failure control
(I) A methodology used to provide fail-safe or fail-soft
termination and recovery of functions and processes when failures
occur or are detected in a system. [FP039]
$ fairness
(I) A property of an access protocol for a system resource whereby
the resource is made equitably or impartially available to all
eligible users. [R3753]
Tutorial: Fairness can prevent flooding, but not jamming.
$ falsification
(I) A type of threat action whereby false data deceives an
authorized entity. (See: active wiretapping, deception.)
Usage: This type includes the following subtypes:
- "Substitution": Altering or replacing valid data with false
data that serves to deceive an authorized entity.
- "Insertion": Introducing false data that serves to deceive an
authorized entity.
$ fault tree
(I) A branching, hierarchical data structure that is used to
represent events and to determine the various combinations of
component failures and human acts that could result in a specified
undesirable system event. (See: attack tree, flaw hypothesis
methodology.)
Tutorial: "Fault-tree analysis" is a technique in which an
undesired state of a system is specified and the system is studied
in the context of its environment and operation to find all
credible ways in which the event could occur. The specified fault
event is represented as the root of the tree. The remainder of the
tree represents AND or OR combinations of subevents, and
sequential combinations of subevents, that could cause the root
event to occur. The main purpose of a fault-tree analysis is to
calculate the probability of the root event, using statistics or
other analytical methods and incorporating actual or predicted
quantitative reliability and maintainability data. When the root
event is a security violation, and some of the subevents are
deliberate acts intended to achieve the root event, then the fault
tree is an attack tree.
$ FEAL
(O) A family of symmetric block ciphers that was developed in
Japan; uses a 64-bit block, keys of either 64 or 128 bits, and a
variable number of rounds; and has been successfully attacked by
cryptanalysts. [Schn]
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$ Federal Information Processing Standards (FIPS)
(N) The Federal Information Processing Standards Publication (FIPS
PUB) series issued by NIST as technical guidelines for U.S.
Government procurements of information processing system equipment
and services. [FP031, FP039, FP041, FP046, FP074, FP081, FP087,
FP102, FP113, FP140, FP151, FP180, FP185, FP186, FP188, FP191,
FP197]
Tutorial: Issued under the provisions of section 111(d) of the
Federal Property and Administrative Services Act of 1949 as
amended by the Computer Security Act of 1987 (Public Law 100-235).
$ Federal Public-key Infrastructure (FPKI)
(O) A PKI being planned to establish facilities, specifications,
and policies needed by the U.S. Government to use public-key
certificates in systems involving unclassified but sensitive
applications and interactions between Federal agencies as well as
with entities of other branches of the Federal Government, state,
and local governments, business, and the public. [FPKI]
$ Federal Standard 1027
(N) An U.S. Government document defining emanation, anti-tamper,
security fault analysis, and manual key management criteria for
DES encryption devices, primary for OSIRM layer 2. Was renamed
"FIPS PUB 140" when responsibility for protecting unclassified,
sensitive information was transferred from NSA to NIST, and has
since been superseded by newer versions of that standard [FP140].
$ File Transfer Protocol (FTP)
(I) A TCP-based, application-level, Internet Standard protocol
(RFC 959) for moving data files from one computer to another.
$ fill device
(N) /COMSEC/ A device used to transfer or store keying material in
electronic form or to insert keying material into cryptographic
equipment.
$ filter
(I) Synonym for "guard". (Compare: content filter, filtering
router.)
$ filtering router
(I) An internetwork router that selectively prevents the passage
of data packets according to a security policy. (See: guard.)
Tutorial: A router usually receives a packet from a network and
decides where to forward it on a second network. A filtering
router does the same, but first decides whether the packet should
be forwarded at all, according to some security policy. The policy
is implemented by rules (packet filters) loaded into the router.
The rules mostly involve values of data packet control fields
(especially IP source and destination addresses and TCP port
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numbers) [R2179]. A filtering router may be used as a firewall or
part of a firewall.
$ financial institution
(N) "An establishment responsible for facilitating customer-
initiated transactions or transmission of funds for the extension
of credit or the custody, loan, exchange, or issuance of money."
[SET2]
$ fingerprint
1. (I) A pattern of curves formed by the ridges on a fingertip.
(See: biometric authentication, thumbprint.)
2. (O) PGP usage: A hash result used to authenticate a public key
(key fingerprint) or other data. [PGP]
Deprecated Definition: ISDs SHOULD NOT use this term with the
specific PGP definition, and SHOULD NOT use this term as a synonym
for "hash result" of *any* kind, because either use would mix
concepts in a potentially misleading way.
$ FIPS
(N) See: Federal Information Processing Standards.
$ FIPS PUB 140-1
(N) The U.S. Government standard [FP140] for security requirements
to be met by a cryptographic module used to protect unclassified
information in computer and communication systems. (See: Common
Criteria, FIPS, Federal Standard 1027.)
Tutorial: The standard specifies four increasing levels (from
"Level 1" to "Level 4") of requirements to cover a wide range of
potential applications and environments. The requirements address
basic design and documentation, module interfaces, authorized
roles and services, physical security, software security,
operating system security, key management, cryptographic
algorithms, electromagnetic interference and electromagnetic
compatibility (EMI/EMC), and self-testing. NIST and the Canadian
Communication Security Establishment jointly certify modules.
$ FIREFLY
(O) /U.S. Government/ "Key management protocol based on public-key
cryptography." [C4009]
$ firewall
1. (I) An internetwork gateway that restricts data communication
traffic to and from one of the connected networks (the one said to
be "inside" the firewall) and thus protects that network's system
resources against threats from the other network (the one that is
said to be "outside" the firewall). (See: guard, security
gateway.)
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2. (O) A device or system that controls the flow of traffic
between networks using differing security postures. [SP41]
Tutorial: A firewall typically protects a smaller, secure network
(such as a corporate LAN, or even just one host) from a larger
network (such as the Internet). The firewall is installed at the
point where the networks connect, and the firewall applies
security policy rules to control traffic that flows in and out of
the protected network.
A firewall is not always a single computer. For example, a
firewall may consist of a pair of filtering routers and one or
more proxy servers running on one or more bastion hosts, all
connected to a small, dedicated LAN (see: DMZ) between the two
routers. The external router blocks attacks that use IP to break
security (IP address spoofing, source routing, packet fragments),
while proxy servers block attacks that would exploit a
vulnerability in a higher layer protocol or service. The internal
router blocks traffic from leaving the protected network except
through the proxy servers. The difficult part is defining criteria
by which packets are denied passage through the firewall, because
a firewall not only needs to keep intruders out, but usually also
needs to let authorized users in and out.
$ firmware
(I) Computer programs and data stored in hardware -- typically in
read-only memory (ROM) or programmable read-only memory (PROM) --
such that the programs and data cannot be dynamically written or
modified during execution of the programs. (See: hardware,
software.)
$ FIRST
(N) See: Forum of Incident Response and Security Teams.
$ flaw
(I) An error of commission, omission, or oversight in the design,
implementation, or operation of an information system. A flaw may
result in a vulnerability. (Compare: vulnerability.)
$ flaw hypothesis methodology
(I) An evaluation or attack technique in which specifications and
documentation for a system are analyzed to hypothesize flaws in
the system. The list of hypothetical flaws is prioritized on the
basis of the estimated probability that a flaw exists and,
assuming it does, on the ease of exploiting it and the extent of
control or compromise it would provide. The prioritized list is
used to direct a penetration test or attack against the system.
[NCS04] (See: fault tree.)
$ flooding
1. (I) An attack that attempts to cause a failure in a system by
providing more input than the system can process properly. (See:
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denial of service, fairness. Compare: jamming.)
Tutorial: Flooding uses "overload" as a type of "obstruction"
intended to cause "disruption".
2. (I) The process of delivering data or control messages to every
node of a network. [R3753]
$ flow analysis
(I) An analysis performed on a nonprocedural formal system
specification that locates potential flows of information between
system variables. By assigning security levels to the variables,
the analysis can find some types of covert channels. [Huff]
$ flow control
(I) A procedure or technique to ensure that information transfers
within a system are not made from one security level to another
security level, and especially not from a higher level to a lower
level. [Denns] (See: covert channel, confinement property,
information flow policy, simple security property.)
$ For Official Use Only (FOUO)
(O) /U.S. DoD/ A U.S. Government designation for information that
has not been given a security classification pursuant to the
criteria of an Executive Order dealing with national security, but
which may be withheld from the public because disclosure would
cause a foreseeable harm to an interest protected by one of the
exemptions stated in the Freedom of Information Act (Section 552
of title 5, United States Code). (See: security label, security
marking. Compare: classified.)
$ formal
(I) Expressed in a restricted syntax language with defined
semantics based on well-established mathematical concepts. [CCIB]
(Compare: informal, semiformal.)
$ Formal Development Methodology
See: Ina Jo.
$ formal model
(I) A security model that is formal. Example: Bell-LaPadula model.
(See: formal, security model.) [Land]
$ formal proof
(I) A complete and convincing mathematical argument presenting the
full logical justification for each step in the proof of the truth
of a theorem or set of theorems.
$ formal specification
(I) A specification of hardware or software functionality in a
computer-readable language; usually a precise mathematical
description of the behavior of the system with the aim of
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providing a correctness proof. [Huff] (See: Affirm, Gypsy, HDM,
Ina Jo.)
$ formulary
(I) A technique for enabling a decision to grant or deny access to
be made dynamically at the time the access is attempted, rather
than earlier when an access control list or ticket is created.
$ FORTEZZA(trademark)
(N) A registered trademark of NSA, used for a family of
interoperable security products that implement a NIST/NSA-approved
suite of cryptographic algorithms for digital signature, hash,
encryption, and key exchange. The products include a PC card (that
contains a CAPSTONE chip), and compatible serial port modems,
server boards, and software implementations.
$ Forum of Incident Response and Security Teams (FIRST)
(N) An international consortium of CSIRTs (e.g., CIAC) that work
together to handle computer security incidents and promote
preventive activities. (See: CSIRT, security incident.)
Tutorial: FIRST was founded in 1990 and, as of July 2004, had more
than 100 members spanning the globe. Its mission includes:
- Provide members with technical information, tools, methods,
assistance, and guidance.
- Coordinate proactive liaison activities and analytical support.
- Encourage development of quality products and services.
- Improve national and international information security for
government, private industry, academia, and the individual.
- Enhance the image and status of the CSIRT community.
$ forward secrecy
See: public-key forward secrecy.
$ FOUO
(O) See: For Official Use Only.
$ FPKI
(O) See: Federal Public-Key Infrastructure.
$ frequency hopping
(N) "Repeated switching of frequencies during radio transmission
according to a specified algorithm." [C4009] (See: spread
spectrum.)
Tutorial: Frequency hopping is a TRANSEC technique to minimize the
potential for unauthorized interception or jamming.
$ FTP
(I) See: File Transfer Protocol.
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$ gateway
(I) An intermediate system (interface, relay) that attaches to two
(or more) computer networks that have similar functions but
dissimilar implementations and that enables inter-network
communication. (See: bridge, firewall, guard, internetwork, proxy
server, router, and subnetwork.)
Tutorial: The networks may differ in any of several aspects,
including protocols and security mechanisms. When two computer
networks differ in the protocol by which they offer service to
hosts, a gateway may translate one protocol into the other or
otherwise facilitate interoperation of hosts (see: Internet
Protocol). In theory, gateways between computer networks are
conceivable at any OSIRM layer. In practice, they usually operate
at OSIRM layer 2 (see: bridge), 3 (see: router), or 7 (see: proxy
server).
$ GCA
(O) See: geopolitical certificate authority.
$ GDOI
(O) See: Group Domain of Interpretation.
$ GeldKarte
(O) A smartcard-based electronic money system that is maintained
by the German banking industry, incorporates cryptography, and can
be used to make payments via the Internet. (See: IOTP.)
$ GeneralizedTime
(N) The ASN.1 data type "GeneralizedTime" (ISO 8601) contains a
calendar date (YYYYMMDD) and a time of day, which is either (a)
the local time, (b) the Coordinated Universal Time, or (c) both
the local time and an offset allowing Coordinated Universal Time
to be calculated. (See: Coordinated Universal Time, UTCTime.)
$ Generic Security Service Application Program Interface (GSS-API)
(I) An Internet Standard protocol [R2078] that specifies calling
conventions by which an application (typically another
communication protocol) can obtain authentication, integrity, and
confidentiality security services independently of the underlying
security mechanisms and technologies, thus allowing the
application source code to be ported to different environments.
Tutorial: "A GSS-API caller accepts tokens provided to it by its
local GSS-API implementation and transfers the tokens to a peer on
a remote system; that peer passes the received tokens to its local
GSS-API implementation for processing. The security services
available through GSS-API in this fashion are implementable (and
have been implemented) over a range of underlying mechanisms based
on [symmetric] and [asymmetric cryptography]." [R2078]
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$ geopolitical certificate authority (GCA)
(O) /SET/ In a SET certification hierarchy, an optional level that
is certified by a BCA and that may certify cardholder CAs,
merchant CAs, and payment gateway CAs. Using GCAs enables a brand
to distribute responsibility for managing certificates to
geographic or political regions, so that brand policies can vary
between regions as needed.
$ GIG
(O) See: Global Information Grid.
$ Global Information Grid.
(O) /U.S. DoD/ "A globally interconnected, end-to-end set of
information capabilities, associated processes and personnel for
collecting, processing, storing, disseminating, and managing
information on demand to warfighters, policy makers, and support
personnel." [IATF]
$ granularity
1. (N) "Relative fineness to which an access control mechanism can
be adjusted." [C4009]
2. (O) "The size of the smallest protectable unit of information"
in a trusted computer system. [Huff]
$ Green Book
(D) Synonym for "Defense Password Management Guideline" [CSC2].
Deprecated Term: Except as an explanatory appositive, ISDs SHOULD
NOT use this term, regardless of the associated definition.
Instead, use the full proper name of the document or, in
subsequent references, a conventional abbreviation. (See: Rainbow
Series.)
Deprecated Usage: To improve international comprehensibility of
Internet Standards and the Internet Standards Process, ISDs SHOULD
NOT use "cute" synonyms. No matter how clearly understood or
popular a nickname may be in one community, it is likely to cause
confusion or offense in others. For example, several other
information system standards also are called "the Green Book". The
following are examples:
- Each volume of 1992 ITU-T (known at that time as CCITT)
standards.
- "PostScript Language Program Design", Adobe Systems, Addison-
Wesley, 1988.
- IEEE 1003.1 POSIX Operating Systems Interface.
- "Smalltalk-80: Bits of History, Words of Advice", Glenn
Krasner, Addison-Wesley, 1983.
- "X/Open Compatibility Guide".
- A particular CD-ROM format developed by Phillips.
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$ GRIP
(I) A contraction of "Guidelines and Recommendations for Security
Incident Processing", the name of the IETF working group that
seeks to facilitate consistent handling of security incidents in
the Internet community. (See: security incident.)
Tutorial: Guidelines to be produced by the WG will address
technology vendors, network service providers, and response teams
in their roles assisting organizations in resolving security
incidents. These relationships are functional and can exist within
and across organizational boundaries.
$ Group Domain of Interpretation (GDOI)
(I) An ISAMKP/IKE domain of interpretation for group key
management; i.e., a phase 2 protocol in ISAKMP. [R3547] (See:
secure multicast.)
Tutorial: In this group key management model that extends the
ISAKMP standard, the protocol is run between a group member and a
"group controller/key server", which establishes security
associations [R2401] among authorized group members. The GDOI
protocol is itself protected by an ISAKMP phase 1 association.
For example, multicast applications may use ESP to protect their
data traffic. GDOI carries the needed security association
parameters for ESP. In this way, GDOI supports multicast ESP with
group authentication of ESP packets using a shared, group key.
$ group identity
(I) See: (secondary definition under) identity.
$ group security association
(I) "A bundling of [security associations] (SAs) that together
define how a group communicates securely. The [group SA] may
include a registration protocol SA, a rekey protocol SA, and one
or more data security protocol SAs." [R3740]
$ GSS-API
(I) See: Generic Security Service Application Program Interface.
$ guard
(I) A computer system that acts as gateway between two information
systems operating under different security policies and is trusted
to mediate information data transfers between the two systems.
(See: controlled interface, domain.)
Usage: Frequently understood to mean that one system is operating
at a higher security level than the other, and that the gateway's
purpose is to prevent unauthorized disclosure of data from the
higher system to the lower. However, the purpose might also be to
protect the data integrity, availability, or general system
integrity of one system from threats posed by connecting to the
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other system. The mediation may be entirely automated or may
involve reliable human review. (See: filter, firewall.)
$ guest login
(I) See: anonymous login.
$ GULS
(I) Generic Upper Layer Security service element (ISO 11586), a
five-part standard for the exchange of security information and
security-transformation functions that protect confidentiality and
integrity of application data.
$ Gypsy verification environment
(O) A methodology, language, and integrated set of software tools
developed at the University of Texas for specifying, coding, and
verifying software to produce correct and reliable programs.
[Cheh]
$ H field
(D) See: Handling Restrictions field.
$ hacker
(I) Someone with a strong interest in computers, who enjoys
learning about them and experimenting with them. (See: cracker.)
Usage: The recommended definition is the original meaning of the
term (circa 1960), which then had a neutral or positive
connotation of "someone who figures things out and makes something
cool happen". Today, the term is frequently misused, especially by
journalists, to have the pejorative meaning of "cracker".
$ handle
1. (I) /verb/ Perform processing operations on data, such as
receive and transmit, collect and disseminate, create and delete,
store and retrieve, read and write, and compare. (See: access.)
2. (I) /noun/ An on-line pseudonym, particularly one used by a
cracker; derived from citizens band radio culture.
$ handling restriction
(I) A type of access control other than (a) the rule-based
protections of mandatory access control and (b) the identity-based
protections of discretionary access control; usually procedural in
nature.
$ Handling Restrictions field
(I) A 16-bit field (the "H field") that specifies a control and
release marking in the security option (option type 130) of IP's
datagram header format. The valid field values are alphanumeric
digraphs assigned by the U.S. Government, as specified in RFC 791.
Deprecated Abbreviation: ISDs SHOULD NOT use the abbreviation "H
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field" because it is potentially ambiguous. Instead, use "Handling
Restrictions field".
$ handshake
(I) Protocol dialogue between two systems for identifying and
authenticating themselves to each other, or for synchronizing
their operations with each other.
$ Handshake Protocol
(I) /TLS/ The TLS Handshake Protocol consists of three sub-
protocols that enable peer entities to agree upon security
parameters for the record layer, authenticate themselves to each
other, instantiate negotiated security parameters, and report
error conditions to each other. [R2246]
$ harden
(I) To protect a system by configuring it to operate in a way that
eliminates or mitigates known vulnerabilities.
$ hardware
(I) The material physical components of an information system.
(See: firmware, software.)
$ hardware token
See: token.
$ hash code
Deprecated Term: ISDs SHOULD NOT use this term (especially not as
a synonym for "hash result" or "hash function"); the term mixes
concepts in a potentially misleading way. A hash result is not a
"code", and a hash function does not "encode" in any sense defined
by this glossary. (See: hash value, message digest.)
$ hash function
1. (I) A function H that maps an arbitrary, variable-length bit
string, s, into a fixed-length string, h = H(s) (called the "hash
result"). For most computing applications, it is desirable that
given a string s with H(s) = h, any change to s that creates a
different string s' will result in an unpredictable hash result
H(s') that is, with high probability, not equal to H(s).
2. (O) "A (mathematical) function which maps values from a large
(possibly very large) domain into a smaller range. A 'good' hash
function is such that the results of applying the function to a
(large) set of values in the domain will be evenly distributed
(and apparently at random) over the range." [X509]
Tutorial: A hash function operates on variable-length input (e.g.,
a message or a file) and outputs a fixed-length output, which
typically is shorter than most input values. If the algorithm is
"good" as described in the "O" definition, then the hash function
may be a candidate for use in a security mechanism to detect
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accidental changes in data, but not necessarily for a mechanism to
detect changes made by active wiretapping (See: (discussion under)
checksum).
Security mechanisms require a "cryptographic hash function" (e.g.,
MD2, MD4, MD5, SHA-1, Snefru), i.e., a good hash function that
also has the one-way property and one of the two collision-free
properties:
- "One-way property": Given H and a hash result h = H(s), it is
hard (i.e., computationally infeasible) to find s. (Of course,
given H and an input s, it must be relatively easy to compute
the hash result H(s).)
- "Weakly collision-free property": Given H and an input s, it is
hard to find a different input, s', such that H(s) = H(s').
- "Strongly collision-free property": Given H, it is hard to find
any pair of inputs s and s' such that H(s) = H(s').
If H produces a hash result N bits long, then to find an s' where
H(s') = H(s) for a specific given s, the amount of computation
required is O(2**n); i.e., it is necessary to try on the order of
2 to the power n values of s' before finding a collision. However,
to simply find any pair of values s and s' that collide, the
amount of computation required is only O(2**(n/2)); i.e., after
computing H(s) for 2 to the power n/2 randomly chosen values of s,
the probability is greater than 1/2 that two of those values have
the same hash result. (See: birthday attack.)
$ hash result
1. (I) The output of a hash function. (See: hash code, hash
value.)
Usage: The "I" definition is recommended to avoid the unusual
usage of "message" that is seen in the following "O" definition.
2. (O) "The output produced by a hash function upon processing a
message" (where "message" is broadly defined as "a digital
representation of data"). [ABA]
$ hash value
(D) Synonym for "hash result".
Deprecated Term: ISDs SHOULD NOT use this term; it could be
confused with "hashed value", which is the input to a hash
function. (See: hash code, hash result, message digest.)
$ HDM
(O) See: Hierarchical Development Methodology.
$ Hierarchical Development Methodology (HDM)
(O) A methodology, language, and integrated set of software tools
developed at SRI International for specifying, coding, and
verifying software to produce correct and reliable programs.
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[Cheh]
$ hierarchical PKI
(I) A PKI architecture based on a certification hierarchy.
(Compare: mesh PKI, trust-file PKI.)
$ hierarchy management
(I) The process of generating configuration data and issuing
public-key certificates to build and operate a certification
hierarchy. (See: certificate management.)
$ hierarchy of trust
(D) Synonym for "certification hierarchy".
Deprecated Term: ISDs SHOULD NOT use this term; it mixes concepts
in a potentially misleading way. (See: certification hierarchy,
trust, web of trust.)
$ high-assurance guard
(N) "An oxymoron," said Lt. Gen. William H. Campbell, former U.S.
Army chief information officer, speaking at an Armed Forces
Communications and Electronics Association conference.
Deprecated Usage: This term mixes concepts and could easily be
misunderstood; therefore, ISDs that use this term SHOULD state a
definition for it.
$ hijack attack
(I) A form of active wiretapping in which the attacker seizes
control of a previously established communication association.
(See: man-in-the-middle attack, pagejacking, piggyback attack.)
$ HIPAA
(N) Health Information Portability and Accountability Act of 1996,
a U.S. law (Public Law 104-191) that protects the privacy of
patients' medical records and other health information in all
forms, and mandates security for that information, including for
its electronic storage and transmission.
$ HMAC
(I) A keyed hash [R2104] that can be based on any iterated
cryptographic hash (e.g., MD5 or SHA-1), so that the cryptographic
strength of HMAC depends on the properties of the selected
cryptographic hash. (See: [R2202, R2403, R2404].)
Tutorial: Assume that H is a generic cryptographic hash in which a
function is iterated on data blocks of length B bytes. L is the
length of the of hash result of H. K is a secret key of length L
<= K <= B. The values IPAD and OPAD are fixed strings used as
inner and outer padding and defined as follows: IPAD = the byte
0x36 repeated B times, OPAD = the byte 0x5C repeated B times. HMAC
is computed by H(K XOR OPAD, H(K XOR IPAD, inputdata)).
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HMAC has the following goals:
- To use available cryptographic hash functions without
modification, particularly functions that perform well in
software and for which software is freely and widely available.
- To preserve the original performance of the selected hash
without significant degradation.
- To use and handle keys in a simple way.
- To have a well-understood cryptographic analysis of the
strength of the mechanism based on reasonable assumptions about
the underlying hash function.
- To enable easy replacement of the hash function in case a
faster or stronger hash is found or required.
$ honey pot
(D) A system (e.g., a web server) or a system resource (e.g., a
file on a server), that is designed to be attractive to potential
crackers and intruders, like honey is attractive to bears. (See:
entrapment.)
Deprecated Term: It is likely that other cultures have different
metaphors for this concept. Therefore, to ensure international
understanding, ISDs SHOULD NOT use this term. (See: (Deprecated
Usage under) Green Book.)
$ host
1. (I) /general/ A computer that is attached to a communication
subnetwork or internetwork and can use services provided by the
network to exchange data with other attached systems. (See: end
system. Compare: server.)
2. (I) /IPS/ A networked computer that does not forward IP packets
that are not addressed to the computer itself. (Compare: router.)
Derivation: As viewed by its users, a host "entertains" them,
providing application layer services or access to other computers
attached to the network. However, even though some traditional
peripheral service devices, such as printers, can now be
independently connected to networks, they are not usually called
hosts.
$ HTML
(I) See: Hypertext Markup Language.
$ HTTP
(I) See: Hypertext Transfer Protocol.
$ https
(I) When used in the first part of a URL (the part that precedes
the colon and specifies an access scheme or protocol), this term
specifies the use of HTTP enhanced by a security mechanism, which
is usually SSL. (Compare: S-HTTP.)
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$ hybrid encryption
(I) An application of cryptography that combines two or more
encryption algorithms, particularly a combination of symmetric and
asymmetric encryption. Examples: digital envelope, MSP, PEM, PGP.
(Compare: superencryption.)
Tutorial: Asymmetric algorithms require more computation than
equivalently strong symmetric ones. Thus, asymmetric encryption is
not normally used for data confidentiality except to distribute a
symmetric keys in a hybrid encryption scheme, where the symmetric
key is usually very short (in terms of bits) compared to the data
file it protects. (See: bulk key.)
$ hyperlink
(I) In hypertext or hypermedia, an information object (such as a
word, a phrase, or an image; usually highlighted by color or
underscoring) that points (indicates how to connect) to related
information that is located elsewhere and can be retrieved by
activating the link (e.g., by selecting the object with a mouse
pointer and then clicking).
$ hypermedia
(I) A generalization of hypertext; any media that contain
hyperlinks that point to material in the same or another data
object.
$ hypertext
(I) A computer document, or part of a document, that contains
hyperlinks to other documents; i.e., text that contains active
pointers to other text. Usually written in HTML and accessed using
a web browser. (See: hypermedia.)
$ Hypertext Markup Language (HTML)
(I) A platform-independent system of syntax and semantics (RFC
1866) for adding characters to data files (particularly text
files) to represent the data's structure and to point to related
data, thus creating hypertext for use in the World Wide Web and
other applications. (Compare: XML.)
$ Hypertext Transfer Protocol (HTTP)
(I) An TCP-based, application-level, client-server, Internet
protocol (RFC 2616) that is used to carry data requests and
responses in the World Wide Web. (See: hypertext.)
$ IAB
(I) See: Internet Architecture Board.
$ IANA
(I) See: Internet Assigned Numbers Authority.
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$ IATF
(O) See: Information Assurance Technical Framework.
$ ICANN
(I) See: Internet Corporation for Assigned Names and Numbers.
$ ICMP
(I) See: Internet Control Message Protocol.
$ ICMP flood
(I) A denial-of-service attack that sends a host more ICMP echo
request ("ping") packets than the protocol implementation can
handle. (See: flooding, smurf.)
$ ICRL
(N) See: indirect certificate revocation list.
$ IDEA
(N) See: International Data Encryption Algorithm.
$ identification
(I) An act or process that presents an identifier to a system so
that the system can recognize a system entity and distinguish it
from other entities. (See: authentication.)
$ identification information
(D) Synonym for "identifier" or "authentication information".
(See: authentication.)
Deprecated Term: ISDs SHOULD NOT use this term; it duplicates the
meaning of standardized terms and mixes concepts in a potentially
misleading way. Instead, use "identifier" or "authentication
information ", depending on what is meant.
$ Identification Protocol
(I) An client-server Internet protocol [R1413] for learning the
identity of a user of a particular TCP connection.
Tutorial: Given a TCP port number pair, the server returns a
character string that identifies the owner of that connection on
the server's system. The protocol is not intended for
authorization or access control; at best, it provides additional
auditing information with respect to TCP.
$ identifier
(I) A data object -- often, a printable, non-blank character
string -- that definitively represents a specific identity of a
system entity, distinguishing that identity from all others.
(Compare: identity.)
$ identity
(I) The collective aspect of a set of attribute values (i.e.,
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characteristics) by which a system entity is recognizable or
known, and which is sufficient to distinguish the entity from all
other entities in the system, and also sufficient to distinguish
the identity from any other identities of the same entity. (See:
authenticate. Compare: identifier.)
Tutorial: When a user's identity is registered in a system, the
system may require presentation of evidence that proves both the
user's eligibility to register and the identity's authenticity
(i.e., that the user has the right to claim the identity).
The set of attributes used for identities must, of course, be
sufficient to uniquely represent each entity, i.e., to distinguish
each entity from all others in the system. However, a PKI or other
system may permit a subscriber to have two or more concurrent
identities. (This is different from concurrently associating two
different identifiers with the same identity, and also different
from a single identity concurrently accessing the system in two
different roles. (See: role-based access control.)) Having two or
more identities registered in a system for the same entity implies
that the entity has two separate justifications for registration
eligibility. In that case, the set of attributes used for
identities must be able to uniquely represent multiple identities
for a single entity.
Tutorial: This term relates to some other basic security terms as
shown in the following diagram:
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Relationships: === One-To-One, ==> One-To-Many, <=> Many-to-Many.
+- - - - - - - - - - - - - - - - - - - - - - - - - - +
| PKI System |
+ - - - - + | +------------------+ +-------------------------+ |
| User | | | Subscriber, i.e. | | Subscriber Identity | |
| +-----+ | | | Registered User | | | |
| |Human| | | |(Is System-Unique)| | (Is System-Unique) | |
| |Being| | | | +--------------+ | | +---------------------+ | |
| +-----+ | | | | User's Core | | | | Subscriber | | |
| ^ |===| | Registration | |==>| | Identity's | | |
| | | | | | Data, i.e., | | | | Registration Data | | |
| | | | | | An Entity's | | | |+-------------------+| | |
| v | | | |Distinguishing|========| Same Core Data || | |
| +-----+ | | | | Attribute | | | ||For All Identities || | |
| | Set | | | | | Values | | +===|| Of The Same User || | |
| +-----+ | | | +--------------+ | | | |+-------------------+| | |
| ^ | | +------------------+ | | +---------------------+ | |
| | | | | +=======+ +------------|------------+ |
| | | | +-------v----|----------------------|------------+ |
| v | | | +----------v-----+ +------------v----------+ | |
| +-----+ | | | | Authentication |<=>| Subscriber Identifier | | |
| |Auto-| | | | | Information | | (Is System Unique) | | |
| |mated| | | | +----------------+ +-----------------------+ | |
| |Pro- | | | | Identity Credential | |
| |cess | | | |(Associates Authentication Info. and Identifier)| |
| +-----+ | | +------------------------------------------------+ |
+ - - - - + + - - - - - - - - - - - - - - - - - - - - - - - - - -+
An ISD may apply this term to a user that is an individual entity
or one that is a set. If an ISD involves both meanings, the ISD
SHOULD use the following definitions to avoid ambiguity:
- "Singular identity": An identity that is registered for a user
that is exactly one person or one process.
- "Shared identity": An identity that is registered for a user
that is a set of entities of which each member is authorized to
assume the identity individually and for which the registering
system maintains a record of the singular entities that
comprise the set. In this case, we would expect each member
entity to be registered with a singular identity.
- "Group identity": An identity that is registered for a user
that is a set of entities for which the registering system does
not maintain a record of the singular entities that comprise
the set.
$ identity-based security policy
(I) "A security policy based on the identities and/or attributes
of users, a group of users, or entities acting on behalf of the
users and the resources/objects being accessed." [I7498 Part 2]
(See: rule-based security policy.)
$ identity credential
1. (I) See: ("authentication" context under) "credential".
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2. (I) Synonym for "signature certificate.
Usage: The term is used in many ways and could easily be
misunderstood; therefore, ISDs that use this term SHOULD state a
definition for it.
$ identity proofing
(I) A process that vets and verifies the information that is used
to establish the identity of a system entity.
$ IDS
(I) See: intrusion detection system.
$ IEEE
(N) See: Institute of Electrical and Electronics Engineers, Inc.
$ IEEE 802.10
(N) An IEEE committee developing security standards for local area
networks. (See: SILS.)
$ IEEE P1363
(N) An IEEE working group, Standard for Public-Key Cryptography,
engaged in developing a comprehensive reference standard for
asymmetric cryptography. Covers discrete logarithm (e.g., DSA),
elliptic curve, and integer factorization (e.g., RSA); and covers
key agreement, digital signature, and encryption.
$ IESG
(I) See: Internet Engineering Steering Group.
$ IETF
(I) See: Internet Engineering Task Force.
$ IKE
(I) See: IPsec Key Exchange.
$ IMAP4
(I) See: Internet Message Access Protocol, version 4.
$ IMAP4 AUTHENTICATE
(I) A IMAP4 "command" (better described as a transaction type, or
a protocol-within-a-protocol) by which an IMAP4 client optionally
proposes a mechanism to an IMAP4 server to authenticate the client
to the server and provide other security services. (See: POP3.)
Tutorial: If the server accepts the proposal, the command is
followed by performing a challenge-response authentication
protocol and, optionally, negotiating a protection mechanism for
subsequent POP3 interactions. The security mechanisms that are
used by IMAP4 AUTHENTICATE -- including Kerberos, GSSAPI, and
S/Key -- are described in [R1731].
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$ in the clear
(I) Not encrypted. (See: clear text.)
$ Ina Jo
(O) A methodology, language, and integrated set of software tools
developed at the System Development Corporation for specifying,
coding, and verifying software to produce correct and reliable
programs. Also known as the Formal Development Methodology. [Cheh]
$ incapacitation
(I) A type of threat action that prevents or interrupts system
operation by disabling a system component. (See: disruption.)
Usage: This type includes the following subtypes:
- "Malicious logic": In context of incapacitation, any hardware,
firmware, or software (e.g., logic bomb) intentionally
introduced into a system to destroy system functions or
resources. (See: (main entry for) malicious logic.)
- "Physical destruction": Deliberate destruction of a system
component to interrupt or prevent system operation.
- "Human error": In context of incapacitation, action or inaction
that unintentionally disables a system component.
- "Hardware or software error": In context of incapacitation,
error that unintentionally causes failure of a system component
and leads to disruption of system operation.
- "Natural disaster": In context of incapacitation, any "act of
God" (e.g., fire, flood, earthquake, lightning, or wind) that
disables a system component. [FP031 section 2]
$ incident
See: security incident.
$ INCITS
See: (International Committee for Information Technology
Standardization under) ANSI.
$ indicator
(N) An action -- either specific, generalized, or theoretical --
that an adversary might be expected to take in preparation for an
attack. [C4009] (See: attack sensing, warning, and response.)
$ indirect certificate revocation list (ICRL)
(N) In X.509, a CRL that may contain certificate revocation
notifications for certificates issued by CAs other than the issuer
(i.e., signer) of the ICRL.
$ indistinguishability
(I) An attribute of an encryption algorithm that is a
formalization of the notion that the encryption of some string is
indistinguishable from the encryption of an equal-length string of
nonsense. (Compare: semantic security.)
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$ inference
1. (I) A type of threat action that reasons from characteristics
or byproducts of communication and thereby indirectly accesses
sensitive data, but not necessarily the data contained in the
communication. (See: traffic analysis, signal analysis.)
2. (I) A type of threat action that indirectly gains unauthorized
access to sensitive information in a database management system by
correlating query responses with information that is already
known.
$ inference control
(I) Protection of data confidentiality against inference attack.
(See: traffic-flow confidentiality.)
Tutorial: A database management system containing N records about
individuals may be required to provide statistical summaries about
subsets of the population, while not revealing sensitive
information about a single individual. An attacker may try to
obtain sensitive information about an individual by isolating a
desired record at the intersection of a set of overlapping
queries. A system can attempt to prevent this by restricting the
size and overlap of query sets, distorting responses by rounding
or otherwise perturbing database values, and limiting queries to
random samples. However, these techniques may be impractical to
implement or use, and no technique is totally effective. For
example, restricting the minimum size of a query set -- that is,
not responding to queries for which there are fewer than K or more
than N-K records that satisfy the query -- usually cannot prevent
unauthorized disclosure. An attacker can pad small query sets with
extra records, and then remove the effect of the extra records.
The formula for identifying the extra records is called the
"tracker". [Denns]
$ INFOCON
(O) See: information operations condition
$ informal
(N) Expressed in natural language. [CCIB] (Compare: formal,
semiformal.)
$ information
(I) Facts and ideas, which can be represented (encoded) as various
forms of data.
$ information assurance
(N) /U.S. Government/ "Measures that protect and defend
information and information systems by ensuring their availability
integrity, authentication, confidentiality, and non-repudiation.
These measures include providing for restoration of information
systems by incorporating protection, detection, and reaction
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capabilities." [C4009]
$ Information Assurance Technical Framework (IATF)
(O) A publicly available document [IATF], developed through a
collaborative effort by organizations in the U.S. Government and
industry, and issued by NSA. Intended for security managers and
system security engineers as a tutorial and reference document
about security problems in information systems and networks, to
improve awareness of tradeoffs among available technology
solutions and of desired characteristics of security approaches
for particular problems. (See: ISO 17799, [SP14].)
$ information domain
(O) See: (secondary definition under) domain.
$ information domain security policy
(O) See: (secondary definition under) domain.
$ information flow policy
(N) /formal model/ A triple consisting of a set of security
levels (or their equivalent security labels), a binary operator
that maps each pair of security levels into a security level, and
a binary relation on the set that selects a set of pairs of levels
such that information is permitted to flow from an object of the
first level to an object of the second level. (See: flow control,
lattice model.)
$ information operations condition (INFOCON)
(O) /U.S. DoD/ A comprehensive defense posture and response based
on the status of information systems, military operations, and
intelligence assessments of adversary capabilities and intent.
(See: threat)
Derivation: From DEFCON, i.e., defense condition.
Tutorial: The U.S. DoD INFOCON levels are: NORMAL (normal
activity), ALPHA (increased risk of attack), BRAVO (specific risk
of attack), CHARLIE (limited attack), and DELTA (general attack).
$ information security (INFOSEC)
(N) Measures that implement and assure security services in
information systems, including in computer systems (see: COMPUSEC)
and in communication systems (see: COMSEC).
$ information system
(I) An organized assembly of computing and communication resources
and procedures -- i.e., equipment and services, together with
their supporting infrastructure, facilities, and personnel -- that
collect, record, process, store, transport, retrieve, display,
disseminate, or dispose of information to accomplish a specified
set of functions. (See: system entity, system resource.)
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$ Information Technology Security Evaluation Criteria (ITSEC)
(N) A Standard [ITSEC] jointly developed by France, Germany, the
Netherlands, and the United Kingdom for use in the European Union;
accommodates a wider range of security assurance and functionality
combinations than the TCSEC. Superseded by the Common Criteria.
$ INFOSEC
(I) See: information security.
$ ingress filtering
(I) A method [R2267] for countering attacks that use packets with
false IP source addresses, by blocking such packets at the
boundary between connected networks.
Tutorial: Suppose network A of an internet service provider (ISP)
includes a filtering router that is connected to customer network
B, and an attacker in B at IP source address "foo" attempts to
send packets with false source address "bar" into A. The false
address may be either fixed or randomly changing, and it may
either be unreachable or be a forged address that legitimately
exists within either B or some other network C. In ingress
filtering, the ISP's router blocks all inbound packet that arrive
from B with a source address that is not within the range of
legitimately advertised addresses for B. This method does not
prevent all attacks that can originate from B, but the actual
source of such attacks can be more easily traced because the
originating network is known.
$ initialization value (IV)
(I) An input parameter that sets the starting state of a
cryptographic algorithm or mode.
Usage: Sometimes called "initialization vector" or "message
indicator", but ISDs SHOULD NOT use these synonyms because they
mix concepts in potentially confusing ways.
Tutorial: An IV can be used to synchronize one cryptographic
process with another; e.g., CBC, CFB, and OFB use IVs. An IV also
can be used to introduce cryptographic variance (see: salt) in
addition to that provided by a key.
$ initialization vector
(D) /cryptographic function/ Synonym for "initialization value".
Deprecated Term: For consistency, ISDs SHOULD NOT use this term in
the context of cryptographic functions.
$ inside attack
(I) See: (secondary definition under) attack. Compare: insider.)
$ insider
1. (I) A user (usually a person) that accesses a system from a
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position that is inside the system's security perimeter. (Compare:
authorized user, outsider, unauthorized user.)
Tutorial: An insider has been assigned a role that has more
privileges to access system resources than do some other types of
users, or can access those resources without being constrained by
some access controls that are applied to outside users. For
example, a salesclerk is an insider who has access to the cash
register, but a store customer is an outsider.
The actions performed by an insider in accessing the system may be
either authorized or unauthorized; i.e., an insider may act either
as an authorized user or as an unauthorized user.
2. (O) A person with authorized physical access to the system.
Example: In this sense, an office janitor is an insider, but a
burglar or casual visitor is not. [NRC98]
3. (O) A person with an organizational status that causes the
system or members of the organization to view access requests as
being authorized. Example: In this sense, a purchasing agent is an
insider but a vendor is not. [NRC98]
$ inspectable space
(O) /EMSEC/ "Three-dimensional space surrounding equipment that
process classified and/or sensitive information within which
TEMPEST exploitation is not considered practical or where legal
authority to identify and/or remove a potential TEMPEST
exploitation exists." [C4009]
$ Institute of Electrical and Electronics Engineers, Inc. (IEEE)
(N) The IEEE is a not-for-profit association of approximately
300,000 individual members in 150 countries. The IEEE produces
nearly one third of the world's published literature in electrical
engineering, computers, and control technology; holds hundreds of
major, annual conferences; and maintains more than 800 active
standards, with many more under development. (See: SILS.)
$ integrity
See: data integrity, correctness integrity, source integrity,
system integrity.
$ integrity check
(D) A computation that is part of a mechanism to provide data
integrity service or data origin authentication service. (Compare:
checksum.)
Deprecated Term: ISDs SHOULD NOT use this term as a synonym for
"cryptographic hash" or "protected checksum. This term
unnecessarily duplicates the meaning of other, well-established
terms; this term only mentions integrity, even though the intended
service may be data origin authentication; and not every checksum
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is cryptographically protected.
$ integrity label
(I) A security label that tells the degree of confidence that may
be placed in the data, and may also tell what countermeasures are
required to be applied to protect the data against from alteration
and destruction. (See: integrity. Compare: classification label.)
$ intelligent threat
(I) A circumstance in which an adversary has the technical and
operational capability to detect and exploit a vulnerability and
also has the demonstrated, presumed, or inferred intent to do so.
(See: threat.)
$ interception
(I) A type of threat action whereby an unauthorized entity
directly accesses sensitive data while the data is traveling
between authorized sources and destinations. (See: unauthorized
disclosure.)
Usage: This type includes the following subtypes:
- "Theft": Gaining access to sensitive data by stealing a
shipment of a physical medium, such as a magnetic tape or disk,
that holds the data.
- "Wiretapping (passive)": Monitoring and recording data that is
flowing between two points in a communication system. (See:
wiretapping.)
- "Emanations analysis": Gaining direct knowledge of communicated
data by monitoring and resolving a signal that is emitted by a
system and that contains the data but is not intended to
communicate the data. (See: emanation.)
$ interference
See: (secondary definition under) obstruction.
$ intermediate CA
(D) The CA that issues a cross-certificate to another CA. [X509]
(See: cross-certification.)
Deprecated Term: ISDs SHOULD NOT use this term because it is not
widely known and mixes concepts in a potentially misleading way.
For example, suppose that end entity 1 ("EE1) is in one PKI
("PKI1"), end entity 2 ("EE2) is in another PKI ("PKI2"), and the
root in PKI1 ("CA1") cross-certifies the root CA in PKI2 ("CA2").
Then if EE1 constructs the certification path CA1-to-CA2-to-EE2 to
validate a certificate of EE2, conventional English usage would
describe CA2 as being in the "intermediate" position in that path,
not CA1.
$ internal controls
(I) /computer security/ Functions, features, and technical
characteristics of computer hardware and software, especially of
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operating systems. Includes mechanisms to regulate the operation
of a computer system with regard to access control, flow control,
and inference control. (Compare: external controls.)
$ International Data Encryption Algorithm (IDEA)
(N) A patented, symmetric block cipher that uses a 128-bit key and
operates on 64-bit blocks. [Schn] (See: symmetric cryptography.)
$ International Standard
(N) See: (secondary definition under) ISO.
$ International Traffic in Arms Regulations (ITAR)
(O) Rules issued by the U.S. State Department, by authority of the
Arms Export Control Act (22 U.S.C. 2778), to control export and
import of defense articles and defense services, including
information security systems, such as cryptographic systems, and
TEMPEST suppression technology. (See: type 1 product, Wassenaar
Arrangement.)
$ internet, Internet
1. (I) /not capitalized/ The term "internet" is a popular short
synonym for "internetwork".
2. (I) /capitalized/ "The Internet" is the single, interconnected,
worldwide system of commercial, government, educational, and other
computer networks that share the protocol suite specified by the
IAB [R2026] and the name and address spaces managed by the ICANN.
Tutorial: The set of protocols is called the "Internet Protocol
Suite" (IPS). It also is popularly known as "TCP/IP", because TCP
and IP are two of its most important protocols. The IPS makes it
possible for users of any one of the networks in the Internet to
communicate with, or use services located on, any of the other
networks.
Although the Internet does have architectural principles
(described in RFC 1958), no Internet Standard defines a layered
reference model for the IPS that is similar to the OSIRM. However,
Internet community documents do refer (inconsistently) to layers:
application, socket, transport, internetwork, network, data link,
and physical.
Usage: In this Glossary, Internet protocol layers are referred to
by name to avoid confusing them with OSIRM layers, which are
referred to by number. (See: OSI.)
$ Internet Architecture Board (IAB)
(I) A technical advisory group of the ISOC, chartered by the ISOC
Trustees to provide oversight of Internet architecture and
protocols and, in the context of Internet Standards, a body to
which decisions of the IESG may be appealed. Responsible for
approving appointments to the IESG from among nominees submitted
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by the IETF nominating committee. [R2026]
$ Internet Assigned Numbers Authority (IANA)
(I) From the early days of the Internet, the IANA was chartered by
the ISOC and the U.S. Government's Federal Network Council to be
the central coordination, allocation, and registration body for
parameters for Internet protocols. Superseded by ICANN.
$ Internet Control Message Protocol (ICMP)
(I) An Internet Standard protocol (RFC 792) that is used to report
error conditions during IP datagram processing and to exchange
other information concerning the state of the IP network.
$ Internet Corporation for Assigned Names and Numbers (ICANN)
(I) The non-profit, private corporation that has assumed
responsibility for the IP address space allocation, protocol
parameter assignment, DNS management, and root server system
management functions formerly performed under U.S. Government
contract by IANA and other entities.
Tutorial: The IPS, as defined by the IETF and the IESG, contains
numerous parameters, such as internet addresses, domain names,
autonomous system numbers, protocol numbers, port numbers,
management information base OIDs, including private enterprise
numbers, and many others. The Internet community requires that the
values used in these parameter fields be assigned uniquely. ICANN
makes those assignments as requested and maintains a registry of
the current values.
ICANN was formed in October 1998, by a coalition of the Internet's
business, technical, and academic communities. The U.S. Government
designated ICANN to serve as the global consensus entity with
responsibility for coordinating four key functions for the
Internet: the allocation of IP address space, the assignment of
protocol parameters, and the management of the DNS and the DNS
root server system.
$ Internet Draft
(I) A working document of the IETF, its areas, and its working
groups. (Other groups may also distribute working documents as
Internet Drafts.) An Internet Draft is not an archival document
like an RFC is. Instead, an Internet Draft is a preliminary or
working document that is valid for a maximum of six months and may
be updated, replaced, or made obsolete by other documents at any
time. It is inappropriate to use an Internet Draft as reference
material or to cite it other than as "work in progress".
$ Internet Engineering Steering Group (IESG)
(I) The part of the ISOC responsible for technical management of
IETF activities and administration of the Internet Standards
Process according to procedures approved by the ISOC Trustees.
Directly responsible for actions along the "standards track",
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including final approval of specifications as Internet Standards.
Composed of IETF Area Directors and the IETF chairperson, who also
chairs the IESG. [R2026]
$ Internet Engineering Task Force (IETF)
(I) A self-organized group of people who make contributions to the
development of Internet technology. The principal body engaged in
developing Internet Standards, although not itself a part of the
ISOC. Composed of Working Groups, which are arranged into Areas
(such as the Security Area), each coordinated by one or more Area
Directors. Nominations to the IAB and the IESG are made by a
committee selected at random from regular IETF meeting attendees
who have volunteered. [R2026, R2323]
$ Internet Message Access Protocol, version 4 (IMAP4)
(I) An Internet protocol (RFC 2060) by which a client workstation
can dynamically access a mailbox on a server host to manipulate
and retrieve mail messages that the server has received and is
holding for the client. (See: POP3.)
Tutorial: IMAP4 has mechanisms for optionally authenticating a
client to a server and providing other security services. (See:
IMAP4 AUTHENTICATE.)
$ Internet Open Trading Protocol (IOTP)
(I) An Internet protocol (RFC 2801) proposed as a general
framework for Internet commerce, able to encapsulate transactions
of various proprietary payment systems (e.g., GeldKarte, Mondex,
SET, VisaCash). Provides optional security services by
incorporating various Internet security mechanisms (e.g., MD5) and
protocols (e.g., TLS).
$ Internet Policy Registration Authority (IPRA)
(I) An X.509-compliant CA that is the top CA of the Internet
certification hierarchy operated under the auspices of the ISOC
[R1422]. (See: (PEM usage under) certification hierarchy.)
$ Internet Private Line Interface (IPLI)
(I) A successor to the PLI, updated to use TCP/IP and newer
military-grade COMSEC equipment (TSEC/KG-84). The IPLI was a
portable, modular system that was developed for use in tactical,
packet-radio networks.
$ Internet Protocol (IP)
(I) A Internet Standard protocol (version 4 is specified in RFC
791, and version 6 in RFC 2460) that moves datagrams (discrete
sets of bits) from one computer to another across an internetwork
but does not provide reliable delivery, flow control, sequencing,
or other end-to-end services that TCP provides. (See: IP address,
TCP/IP.)
Tutorial: In the OSIRM, IP would be located at the top of layer 3.
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$ Internet Protocol security
See: IPsec.
$ Internet Protocol Security Option (IPSO)
(I) Refers to one of three types of IP security options, which are
fields that may be added to an IP datagram for the purpose of
carrying security information about the datagram. (Compare:
IPsec.)
Deprecated Usage: ISDs SHOULD NOT use this term without a modifier
to indicate which of the following three types is meant.
- "DoD Basic Security Option" (IP option type 130): Defined for
use on U.S. DoD common-use data networks. Identifies the DoD
classification level at which the datagram is to be protected
and the protection authorities whose rules apply to the
datagram. (A "protection authority" is a National Access
Program (e.g., GENSER, SIOP-ESI, SCI, NSA, Department of
Energy) or Special Access Program that specifies protection
rules for transmission and processing of the information
contained in the datagram.) [R1108]
- "DoD Extended Security Option" (IP option type 133): Permits
additional security labeling information, beyond that present
in the Basic Security Option, to be supplied in the datagram to
meet the needs of registered authorities. [R1108]
- "Common IP Security Option" (CIPSO) (IP option type 134):
Designed by TSIG to carry hierarchic and non-hierarchic
security labels. (Formerly called "Commercial IP Security
Option"; a version 2.3 draft was published 9 Mar 1993 as an
Internet-Draft but did not advance to RFC form.) [CIPSO]
$ Internet Protocol Suite (IPS)
(I) See: (secondary definition under) Internet.
$ Internet Security Association and Key Management Protocol (ISAKMP)
(I) An Internet IPsec protocol [R2408] to negotiate, establish,
modify, and delete security associations, and to exchange key
generation and authentication data, independent of the details of
any specific key generation technique, key establishment protocol,
encryption algorithm, or authentication mechanism.
Tutorial: ISAKMP supports negotiation of security associations for
protocols at all TCP/IP layers. By centralizing management of
security associations, ISAKMP reduces duplicated functionality
within each protocol. ISAKMP can also reduce connection setup
time, by negotiating a whole stack of services at once. Strong
authentication is required on ISAKMP exchanges, and a digital
signature algorithm based on asymmetric cryptography is used
within ISAKMP's authentication component.
ISAKMP includes two "phases" of negotiation: the phase 1
negotiation establishes a basic security association to be used
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for ISAKMP operations. Then, protected by the phase 1 association,
phase 2 negotiations are used to establish security associations
for other protocols, such as ESP.
$ Internet Society (ISOC)
(I) A professional society concerned with Internet development
(including technical Internet Standards); with how the Internet is
and can be used; and with social, political, and technical issues
that result. The ISOC Board of Trustees approves appointments to
the IAB from among nominees submitted by the IETF nominating
committee. [R2026]
$ Internet Standard
(I) A specification, approved by the IESG and published as an RFC,
that is stable and well-understood, is technically competent, has
multiple, independent, and interoperable implementations with
substantial operational experience, enjoys significant public
support, and is recognizably useful in some or all parts of the
Internet. [R2026] (See: RFC.)
Tutorial: The "Internet Standards Process" is an activity of the
ISOC and is organized and managed by the IAB and the IESG. The
process is concerned with all protocols, procedures, and
conventions used in or by the Internet, whether or not they are
part of the IPS. The "Internet Standards Track" has three levels
of increasing maturity: Proposed Standard, Draft Standard, and
Standard. (Compare: ISO, W3C.)
$ Internet Standards document (ISD)
(I) An RFC or an Internet-Draft that is produced as part of the
Internet Standards Process [R2026]. (See: Internet Standard.)
Deprecated Usage: Neither the term nor the abbreviation is widely
accepted; therefore, ISDs that use this term SHOULD state a
definition for it.
$ internetwork
(I) A system of interconnected networks; a network of networks.
Usually shortened to "internet". (See: internet.)
Tutorial: An internet is usually built using OSIRM layer 3
gateways to connect a set of subnetworks. When the subnetworks
differ in the layer 3 protocol service they provide, the gateways
sometimes implement a uniform internetwork protocol (e.g., IP)
that operates at the top of layer 3 and hides the underlying
heterogeneity from hosts that use communication services provided
by the internet. (See: router.)
$ intranet
(I) A computer network, especially one based on Internet
technology, that an organization uses for its own internal, and
usually private, purposes and that is closed to outsiders. (See:
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extranet, virtual private network.)
$ intruder
(I) An entity that gains or attempts to gain access to a system or
system resource without having authorization to do so. (See:
intrusion. Compare: adversary, cracker.)
$ intrusion
1. (I) A security event, or a combination of multiple security
events, that constitutes a security incident in which an intruder
gains, or attempts to gain, access to a system or system resource
without having authorization to do so. (See: IDS.)
2. (I) A type of threat action whereby an unauthorized entity
gains access to sensitive data by circumventing a system's
security protections. (See: unauthorized disclosure.)
Usage: This type includes the following subtypes:
- "Trespass": Gaining physical access to sensitive data by
circumventing a system's protections.
- "Penetration": Gaining logical access to sensitive data by
circumventing a system's protections.
- "Reverse engineering": Acquiring sensitive data by
disassembling and analyzing the design of a system component.
- "Cryptanalysis": Transforming encrypted data into plain text
without having prior knowledge of encryption parameters or
processes. (See: (main Glossary entry for) cryptanalysis.)
$ intrusion detection
(I) Sensing and analyzing system events for the purpose of
noticing (i.e., becoming aware of) attempts to access system
resources in an unauthorized manner. (See: anomaly detection, IDS,
misuse detection.) [IDSAN, IDSSC, IDSSE, IDSSY]
Usage: This includes the following subtypes:
- "Active detection": Real-time or near-real-time analysis of
system event data to detect current intrusions, which result in
an immediate protective response.
- "Passive detection": Off-line analysis of audit data to detect
past intrusions, which are reported to the system security
officer for corrective action. (Compare: security audit.)
$ intrusion detection system (IDS)
1. (N) A process or subsystem, implemented in software or
hardware, that automates the tasks of (a) monitoring events that
occur in a computer network and (b) analyzing them for signs of
security problems. [SP31] (See: intrusion detection.)
2. (N) A security alarm system to detect unauthorized entry.
[DC6/9].
Tutorial: Active intrusion detection processes can be either host-
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based or network-based:
- "Host-based": Intrusion detection components -- traffic sensors
and analyzers -- run directly on the hosts that they are
intended to protect.
- "Network-based": Sensors are placed on subnetwork components,
and analysis components run either on subnetwork components or
hosts.
$ invalidity date
(N) An X.509 CRL entry extension that "indicates the date at which
it is known or suspected that the [revoked certificate's private
key] was compromised or that the certificate should otherwise be
considered invalid." [X509].
Tutorial: This date may be earlier than the revocation date in the
CRL entry, and may even be earlier than the date of issue of
earlier CRLs. However, the invalidity date is not, by itself,
sufficient for purposes of non-repudiation service. For example,
to fraudulently repudiate a validly-generated signature, a private
key holder may falsely claim that the key was compromised at some
time in the past.
$ IOTP
(I) See: Internet Open Trading Protocol.
$ IP
(I) See: Internet Protocol.
$ IP address
(I) A computer's internetwork address that is assigned for use by
IP and other protocols.
Tutorial: An IP version 4 address (RFC 791) is written as a series
of four 8-bit numbers separated by periods. For example, the
address of the host named "rosslyn.bbn.com" is 192.1.7.10.
An IP version 6 address (RFC 2373) is written as x:x:x:x:x:x:x:x,
where each "x" is the hexadecimal value of one of the eight 16-bit
parts of the address. For example, 1080:0:0:0:8:800:200C:417A and
FEDC:BA98:7654:3210:FEDC:BA98:7654:3210.
$ IP Security Option
(I) See: Internet Protocol Security Option.
$ IPLI
(I) See: Internet Private Line Interface.
$ IPRA
(I) See: Internet Policy Registration Authority.
$ IPS
(I) See: Internet Protocol Suite.
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$ IPsec
1a. (I) A contraction of "Internet Protocol security", the name of
the IETF working group that is specifying an architecture [R2401]
and set of protocols to provide security services for IP traffic.
(See: AH, ESP, IKE, SAD, SPD. Compare: IPSO.)
1b. (I) A collective name for that IP security architecture and
associated set of protocols.
Usage: Note that the letters "sec" are in lower case in "IPsec".
Tutorial: The security services provided by IPsec include access
control service, connectionless data integrity service, data
origin authentication service, protection against replays
(detection of the arrival of duplicate datagrams, within a
constrained window), data confidentiality service, and limited
traffic-flow confidentiality. IPsec specifies (a) security
protocols (AH and ESP), (b) security associations (what they are,
how they work, how they are managed, and associated processing),
(c) key management (IKE), and (d) algorithms for authentication
and encryption. Implementation of IPsec is optional for IP version
4, but mandatory for IP version 6.
$ IPsec Key Exchange (IKE)
(I) An Internet, IPsec, key-establishment protocol [R2409] for
putting in place authenticated keying material (a) for use with
ISAKMP and (b) for other security associations, such as in AH and
ESP.
Tutorial: IKE is based on three earlier protocol designs: ISAKMP,
OAKLEY, and SKEME.
$ IPSO
(I) See: Internet Protocol Security Option.
$ ISAKMP
(I) See: Internet Security Association and Key Management
Protocol.
$ ISD
(I) See: Internet Standards document.
$ ISO
(I) International Organization for Standardization, a voluntary,
non-treaty, non-government organization, established in 1947, with
voting members that are designated standards bodies of
participating nations and non-voting observer organizations.
(Compare: ANSI, IETF, ITU-T, W3C.)
Tutorial: Legally, ISO is a Swiss, non-profit, private
organization. ISO and the IEC (the International Electrotechnical
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Commission) form the specialized system for worldwide
standardization. National bodies that are members of ISO or IEC
participate in developing international standards through ISO and
IEC technical committees that deal with particular fields of
activity. Other international governmental and non-governmental
organizations, in liaison with ISO and IEC, also take part. (ANSI
is the U.S. voting member of ISO. ISO is a class D member of
ITU-T.)
The ISO standards development process has four levels of
increasing maturity: Working Draft (WD), Committee Draft (CD),
Draft International Standard (DIS), and International Standard
(IS). (Compare: (standards track levels under) Internet Standard.)
In information technology, ISO and IEC have a joint technical
committee, ISO/IEC JTC 1. DISs adopted by JTC 1 are circulated to
national bodies for voting, and publication as an IS requires
approval by at least 75% of the national bodies casting a vote.
$ ISO 17799
(N) An International Standard that is a code of practice, derived
from Part 1 of British Standard 7799, for managing the security of
information systems in an organization. This standard does not
provide definitive or specific material on any security topic. It
provides general guidance on a wide variety of topics, but
typically does not go into depth. (See: IATF, [SP14].)
$ ISOC
(I) See: Internet Society.
$ issue (a digital certificate or CRL)
(I) Generate and sign a digital certificate (or CRL) and, usually,
distribute it and make it available to potential certificate users
(or CRL users). (See: certificate creation.)
Usage: The ABA Guidelines [ABA] explicitly limit this term to
certificate creation, and exclude the act of publishing. In
general usage, however, "issuing" a digital certificate (or CRL)
includes not only certificate creation but also making it
available to potential users, such as by storing it in a
repository or other directory or otherwise publishing it.
$ issuer
1. (I) /certificate, CRL/ The CA that signs a digital certificate
or CRL.
Tutorial: An X.509 certificate always includes the issuer's name.
The name may include a common name value.
2. (O) /payment card, SET/ "The financial institution or its agent
that issues the unique primary account number to the cardholder
for the payment card brand." [SET2]
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Tutorial: The institution that establishes the account for a
cardholder and issues the payment card also guarantees payment for
authorized transactions that use the card in accordance with card
brand regulations and local legislation. [SET1]
$ ITAR
(O) See: International Traffic in Arms Regulations.
$ ITSEC
(N) See: Information Technology System Evaluation Criteria.
$ ITU-T
(N) International Telecommunications Union, Telecommunication
Standardization Sector (formerly "CCITT"), a United Nations treaty
organization that is composed mainly of postal, telephone, and
telegraph authorities of the member countries and that publishes
standards called "Recommendations". (See: X.400, X.500.)
Tutorial: The Department of State represents the United States.
ITU-T works on many kinds of communication systems. ITU-T
cooperates with ISO on communication protocol standards, and many
Recommendations in that area are also published as an ISO standard
with an ISO name and number.
$ IV
(I) See: initialization value.
$ jamming
(I) An attack that attempts to interfere with the reception of
broadcast communications. (See: anti-jam, denial of service.
Compare: flooding.)
Tutorial: Jamming uses "interference" as a type of "obstruction"
intended to cause "disruption". Jamming a broadcast signal is
typically done by broadcasting a second signal that receivers
cannot separate from the first one. Jamming is mainly thought of
in the context of wireless communication, but also can be done in
some wired technologies, such as LANs that use contention
techniques to share a broadcast medium.
$ KAK
(D) See: key-auto-key. (Compare: KEK.)
$ KDC
(I) See: Key Distribution Center.
$ KEA
(N) See: Key Exchange Algorithm.
$ KEK
(I) See: key-encrypting key. (Compare: KAK.)
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$ Kerberos
(N) A system developed at the Massachusetts Institute of
Technology that depends on passwords and symmetric cryptography
(DES) to implement ticket-based, peer entity authentication
service and access control service distributed in a client-server
network environment. [R1510, Stei]
Tutorial: Kerberos was developed by Project Athena and is named
for the three-headed dog guarding Hades. The system architecture
includes servers that function as an ACC and a KDC.
$ kernel
(I) A small, trusted part of a system that provides services on
which the other parts of the system depend. (See: security
kernel.)
$ Kernelized Secure Operating System (KSOS)
(O) An MLS computer operating system, designed to be a provably
secure replacement for UNIX Version 6, and consisting of a
security kernel, non-kernel security-related utility programs, and
optional UNIX application development and support environments.
[Perr]
Tutorial: KSOS-6 was the implementation on a SCOMP. KSOS-11 was
the implementation by Ford Aerospace and Communications
Corporation on the DEC PDP-11/45 and PDP-111/70 computers.
$ key
1. (I) /cryptography/ An input parameter used to vary a
transformation function performed by a cryptographic algorithm.
(Compare: initialization value.)
2. (I) /anti-jam/ An input parameter used to vary a process that
determines patterns for an anti-jam measure. (See: frequency
hopping, spread spectrum.)
Tutorial: A key is usually specified as a sequence of bits or
other symbols. If a key value needs to be kept secret, the
sequence of symbols that comprise it should be random, or at least
pseudorandom, because that makes the key hard for an adversary to
guess. (See: cryptanalysis, brute force attack.)
$ key agreement (algorithm or protocol)
1. (I) A key establishment method (especially one involving
asymmetric cryptography) by which two or more entities, without
prior arrangement except a public exchange of data (such as public
keys), each can generate the same key value. That is, the method
does not send a secret from one entity to the other (compare: key
transport); instead, both entities, without prior arrangement
except a public exchange of data, can compute the same secret
value, but that value cannot be computed by other, unauthorized
entities. (See: Diffie-Hellman, key establishment, KEA, MQV.)
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2. (O) "A method for negotiating a key value on line without
transferring the key, even in an encrypted form, e.g., the Diffie-
Hellman technique." [X509]
3. (O) "The procedure whereby two different parties generate
shared symmetric keys such that any of the shared symmetric keys
is a function of the information contributed by all legitimate
participants, so that no party [alone] can predetermine the value
of the key." [A9042]
Example: A message originator and the intended recipient can each
use their own private key and the other's public key with the
Diffie-Hellman algorithm to first compute a shared secret value
and, from that value, derive a session key to encrypt the message.
$ key authentication
(N) "The assurance of the legitimate participants in a key
agreement that no non-legitimate party possesses the shared
symmetric key." [A9042]
$ key-auto-key (KAK)
(D) "Cryptographic logic using previous key to produce key."
[C4009, A1523] (See: CTAK.)
Deprecated Term: IDS should not use this term; it is neither well-
known nor precisely defined. Instead, use terms associated with
modes that are defined in standards, such as CBC, CFB, and OFB.
$ key center
(I) A centralized key distribution process (used in symmetric
cryptography), usually a separate computer system, that uses
master keys (i.e., KEKs) to encrypt and distribute session keys
needed in a community of users.
Tutorial: An ANSI standard [A9017] defines two types of key
center: key distribution center and key translation center.
$ key confirmation
(N) "The assurance [provided to] the legitimate participants in a
key establishment protocol that the [parties that are intended to
share] the symmetric key actually possess the shared symmetric
key." [A9042]
$ key distribution
(I) A process that delivers a cryptographic key from the location
where it is generated to the locations where it is used in a
cryptographic algorithm. (See: key management.)
$ key distribution center (KDC)
1. (I) A type of key center (used in symmetric cryptography) that
implements a key distribution protocol to provide keys (usually,
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session keys) to two (or more) entities that wish to communicate
securely. (Compare: key translation center.)
2. (N) "COMSEC facility generating and distributing key in
electrical form." [C4009]
Tutorial: A KDC distributes keys to Alice and Bob, who (a) wish to
communicate with each other but do not currently share keys, (b)
each share a KEK with the KDC, and (c) may not be able to generate
or acquire keys by themselves. Alice requests the keys from the
KDC. The KDC generates or acquires the keys and makes two
identical sets. The KDC encrypts one set in the KEK it shares with
Alice, and sends that encrypted set to Alice. The KDC encrypts the
second set in the KEK it shares with Bob, and either (a) sends
that encrypted set to Alice for her to forward to Bob or (b) sends
it directly to Bob (although the latter option is not supported in
the ANSI standard [A9017]).
$ key encapsulation
(N) A key recovery technique for storing knowledge of a
cryptographic key by encrypting it with another key and ensuring
that that only certain third parties called "recovery agents" can
perform the decryption operation to retrieve the stored key. Key
encapsulation typically permits direct retrieval of a secret key
used to provide data confidentiality. (Compare: key escrow.)
$ key-encrypting key (KEK)
(I) A cryptographic key that (a) is used to encrypt other keys
(either DEKs or other TEKs) for transmission or storage but (b)
usually is not used to encrypt application data. Usage: Sometimes
called "key-encryption key".
$ key escrow
(N) A key recovery technique for storing knowledge of a
cryptographic key or parts thereof in the custody of one or more
third parties called "escrow agents", so that the key can be
recovered and used in specified circumstances. (Compare: key
encapsulation.)
Tutorial: Key escrow is typically implemented with split knowledge
techniques. For example, the Escrowed Encryption Standard [FP185]
entrusts two components of a device-unique split key to separate
escrow agents. The agents provide the components only to someone
legally authorized to conduct electronic surveillance of
telecommunications encrypted by that specific device. The
components are used to reconstruct the device-unique key, and it
is used to obtain the session key needed to decrypt
communications.
$ key establishment (algorithm or protocol)
1. (I) A procedure that combines the key generation and key
distribution steps needed to set up or install a secure
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communication association.
2. (I) A procedure that results in keying material being shared
among two or more system entities. [A9042, SP56]
Tutorial: The two basic techniques for key establishment are "key
agreement" and "key transport".
$ Key Exchange Algorithm (KEA)
(N) A key-agreement method [SKIP, R2773] based on the Diffie-
Hellman algorithm and uses 1024-bit asymmetric keys. (See:
CAPSTONE, CLIPPER, FORTEZZA, SKIPJACK.)
Tutorial: KEA was developed by NSA and formerly classified at the
U.S. DoD "Secret" level. On 23 June 1998, the NSA announced that
KEA had been declassified.
$ key generation
(I) A process that creates the sequence of symbols that comprise a
cryptographic key. (See: key management.)
$ key generator
1. (I) An algorithm that uses mathematical rules to
deterministically produce a pseudorandom sequence of cryptographic
key values.
2. (I) An encryption device that incorporates a key generation
mechanism and applies the key to plain text to produce cipher text
(e.g., by exclusive OR-ing (a) a bit string representation of the
key with (b) a bit string representation of the plaintext).
$ key length
(I) The number of symbols (usually stated as a number of bits)
needed to be able to represent any of the possible values of a
cryptographic key. (See: key space.)
$ key lifetime
(N) /MISSI/ An attribute of a MISSI key pair that specifies a time
span that bounds the validity period of any MISSI X.509 public-key
certificate that contains the public component of the pair. (See:
cryptoperiod.)
$ key loader
(N) Synonym for "fill device".
$ key management
1a. (I) The process of handling keying material during its life
cycle in a cryptographic system; and the supervision and control
of that process. (See: key distribution, key escrow, keying
material, public-key infrastructure.)
Usage: Usually understood to include ordering, generating,
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storing, archiving, escrowing, distributing, loading, destroying,
auditing, and accounting for the material.
1b. (O) /NIST/ "The activities involving the handling of
cryptographic keys and other related security parameters (e.g.,
IVs, counters) during the entire life cycle of the keys, including
their generation, storage, distribution, entry and use, deletion
or destruction, and archiving." [FP140, SP57]
2. (O) /OSIRM/ "The generation, storage, distribution, deletion,
archiving and application of keys in accordance with a security
policy." [I7498 Part 2]
$ Key Management Protocol (KMP)
(N) A protocol to establish a shared symmetric key between a pair
(or a group) of users. (One version of KMP was developed by SDNS,
and another by SILS.) Superseded by ISAKMP and IKE.
$ key material
(D) A synonym for "keying material".
Deprecated Usage: ISDs SHOULD NOT use this term as a synonym for
"keying material".
$ key pair
(I) A set of mathematically related keys -- a public key and a
private key -- that are used for asymmetric cryptography and are
generated in a way that makes it computationally infeasible to
derive the private key from knowledge of the public key. (See:
Diffie-Hellman, RSA.)
Tutorial: A key pair's owner discloses the public key to other
system entities so they can use the key to (a) encrypt data, (b)
verify a digital signature, (c) compute a protected checksum, or
(d) generate a key in a key agreement algorithm. The matching
private key is kept secret by the owner, who uses it to (a')
decrypt data, (b') generate a digital signature, (c') verify a
protected checksum, or (d') generate a key in a key agreement
algorithm.
$ key recovery
1. (I) /cryptanalysis/ A process for learning the value of a
cryptographic key that was previously used to perform some
cryptographic operation. (See: cryptanalysis, recovery.)
2. (I) /backup/ Techniques that provide an intentional, alternate,
means to access the key used for data confidentiality service in
an encrypted association. [DoD4] (Compare: recovery.)
Tutorial: It is assumed that the cryptographic system includes a
primary means of obtaining the key through a key establishment
algorithm or protocol. For the secondary means, there are two
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classes of key recovery techniques: key encapsulation and key
escrow.
$ key space
(I) The range of possible values of a cryptographic key; or the
number of distinct transformations supported by a particular
cryptographic algorithm. (See: key length.)
$ key translation center
(I) A type of key center that implements a key distribution
protocol (based on symmetric cryptography) to convey keys between
two (or more) parties who wish to communicate securely. (Compare:
key distribution center.)
Tutorial: A key translation center transfers keys for future
communication between Bob and Alice, who (a) wish to communicate
with each other but do not currently share keys, (b) each share a
KEK with the center, and (c) have the ability to generate or
acquire keys by themselves. Alice generates or acquires a set of
keys for communication with Bob. Alice encrypts the set in the KEK
she shares with the center and sends the encrypted set to the
center. The center decrypts the set, reencrypts the set in the KEK
it shares with Bob, and either (a) sends that reencrypted set to
Alice for her to forward to Bob or (b) sends it directly to Bob
(although direct distribution is not supported in the ANSI
standard [A9017]).
$ key transport (algorithm or protocol)
1. (I) A key establishment method by which a secret key is
generated by a system entity in a communication association and
securely sent to another entity in the association. (Compare: key
agreement.)
Tutorial: Either (a) one entity generates a secret key and
securely sends it to the other entity, or (b) each entity
generates a secret value and securely sends it to the other
entity, where the two values are combined to form a secret key.
For example, a message originator can generate a random session
key and then use the RSA algorithm to encrypt that key with the
public key of the intended recipient.
2. (O) "The procedure to send a symmetric key from one party to
other parties. As a result, all legitimate participants share a
common symmetric key in such a way that the symmetric key is
determined entirely by one party." [A9042]
$ key update
1. (I) Derive a new key from an existing key. (Compare: rekey.)
2. (O) Irreversible cryptographic process that modifies a key to
produce a new key. [C4009]
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$ key validation
1. (I) "The procedure for the receiver of a public key to check
that the key conforms to the arithmetic requirements for such a
key in order to thwart certain types of attacks." [A9042] (See:
weak key)
2. (D) A synonym for "certificate validation".
Deprecated Usage: ISDs SHOULD NOT use the term as a synonym for
"certificate validation"; that would unnecessarily duplicate the
meaning of the latter term and mix concepts in a potentially
misleading way. In validating an X.509 public-key certificate, the
public key contained in the certificate is normally treated as an
opaque data object.
$ keyed hash
(I) A cryptographic hash (e.g., [R1828]) in which the mapping to a
hash result is varied by a second input parameter that is a
cryptographic key. (See: checksum.)
Tutorial: If the input data object is changed, a new,
corresponding hash result cannot be correctly computed without
knowledge of the secret key. Thus, the secret key protects the
hash result so it can be used as a checksum even when there is a
threat of an active attack on the data. There are two basic types
of keyed hash:
- A function based on a keyed encryption algorithm. Example: Data
Authentication Code.
- A function based on a keyless hash that is enhanced by
combining (e.g., by concatenating) the input data object
parameter with a key parameter before mapping to the hash
result. Example: HMAC.
$ keying material
(I) Data that is needed to establish and maintain a cryptographic
security association, such as keys, key pairs, and IVs.
(O) "Key, code, or authentication information in physical or
magnetic form." [C4009] (Compare: COMSEC material.)
$ keying material identifier (KMID)
1. (I) An identifier assigned to an item of keying material.
2. (O) /MISSI/ A 64-bit identifier that is assigned to a key pair
when the public key is bound in a MISSI X.509 public-key
certificate.
$ Khafre
(N) A patented, symmetric block cipher designed by Ralph C. Merkle
as a plug-in replacement for DES. [Schn]
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Tutorial: Khafre was designed for efficient encryption of small
amounts of data. However, because Khafre does not precompute
tables used for encryption, it is slower than Khufu for large
amounts of data.
$ Khufu
(N) A patented, symmetric block cipher designed by Ralph C. Merkle
as a plug-in replacement for DES. [Schn]
Tutorial: Khufu was designed for fast encryption of large amounts
of data. However, because Khufu precomputes tables used in
encryption, it is less efficient that Khafre for small amounts of
data.
$ KMID
(I) See: keying material identifier.
$ known-plaintext attack
(I) A cryptanalysis technique in which the analyst tries to
determine the key from knowledge of some plaintext-ciphertext
pairs (although the analyst may also have other clues, such as the
knowing the cryptographic algorithm).
$ KSOS, KSOS-6, KSOS-11
(O) See: Kernelized Secure Operating System.
$ L2F
(N) See: Layer 2 Forwarding Protocol.
$ L2TP
(N) See: Layer 2 Tunneling Protocol.
$ label
See: time stamp, security label.
$ laboratory attack
(O) "Use of sophisticated signal recovery equipment in a
laboratory environment to recover information from data storage
media." [C4009]
$ LAN
(I) Local area network.
$ land attack
(I) A denial-of-service attack that sends an IP packet that (a)
has the same address in both the Source Address and Destination
Address fields and (b) contains a TCP SYN packet that has the same
port number in both the Source Port and Destination Port fields.
Derivation: This single-packet attack was named for "land", the
program originally published by the cracker who invented this
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exploit. Perhaps that name was chosen because the inventor thought
of multi-packet (i.e., flooding) attacks as arriving by "sea".
$ Language of Temporal Ordering Specification (LOTOS)
(N) A language (ISO 8807-1990) for formal specification of
computer network protocols; describes the order in which events
occur.
$ lattice
(I) A finite set together with a partial ordering on its elements
such that for every pair of elements there is a least upper bound
and a greatest lower bound.
Example: A lattice is formed by a finite set S of security levels
-- i.e., a set S of all ordered pairs (x,c), where x is one of a
finite set X of hierarchically ordered classification levels X(1),
non-hierarchical categories C(1), ..., C(M) -- together with the
"dominate" relation. Security level (x,c) is said to "dominate"
(x',c') if and only if (a) x is greater (higher) than or equal to
x' and (b) c includes at least all of the elements of c'. (See:
dominate, lattice model.)
$ lattice model
1. (I) A description of the semantic structure formed by a finite
set of security levels, such as those used in military
organizations. (See: dominate, security model.)
2. (I) /formal model/ A model for flow control in a system, based
on the lattice that is formed by the finite security levels in a
system and their partial ordering. [Denn]
$ Law Enforcement Access Field (LEAF)
(N) A data item that is automatically embedded in data encrypted
by devices (e.g., CLIPPER chip) that implement the Escrowed
Encryption Standard.
$ layer 1, 2, 3, 4, 5, 6, 7
(N) See: OSIRM.
$ Layer 2 Forwarding Protocol (L2F)
(N) An Internet protocol (originally developed by Cisco
Corporation) that uses tunneling of PPP over IP to create a
virtual extension of a dial-up link across a network, initiated by
the dial-up server and transparent to the dial-up user. (See:
L2TP.)
$ Layer 2 Tunneling Protocol (L2TP)
(N) An Internet client-server protocol that combines aspects of
PPTP and L2F and supports tunneling of PPP over an IP network or
over frame relay or other switched network. (See: virtual private
network.)
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Tutorial: PPP can in turn encapsulate any OSIRM layer 3 protocol.
Thus, L2TP does not specify security services; it depends on
protocols layered above and below it to provide any needed
security.
$ LDAP
(I) See: Lightweight Directory Access Protocol.
$ least common mechanism
(I) The principle that a security architecture should minimize
reliance on mechanisms that are shared by many users.
Tutorial: Shared mechanisms may include cross-talk paths that
permit a breach of data security, and it is difficult to make a
single mechanism operate in a correct and trusted manner to the
satisfaction of a wide range of users.
$ least privilege
(I) The principle that a security architecture should be designed
so that each system entity is granted the minimum system resources
and authorizations that the entity needs to do its work. (Compare:
economy of mechanism, least trust.)
Tutorial: This principle tends to limit damage that can be caused
by an accident, error, or unauthorized act. This principle also
tends to reduce complexity and promote modularity, which can make
certification easier and more effective. This principle is similar
to the principle of protocol layering, wherein each layer provides
specific, limited communication services, and the functions in one
layer are independent of those in other layers.
$ least trust
(I) The principle that a security architecture should be designed
in a way that minimizes (a) the number of components that require
trust and (b) the extent to which each component is trusted.
(Compare: least privilege, trust level.)
$ legacy system
(I) A system that is in operation but will not be improved or
expanded while a new system is being developed to supersede it.
$ legal non-repudiation
(I) See: (secondary definition under) non-repudiation.
$ level of concern
(N) /U.S. DoD/ A rating assigned to an information system that
indicates the extent to which protective measures, techniques, and
procedures must be applied. (See: level of robustness.)
$ level of robustness
(N) /U.S. DoD/ A characterization of the strength of a security
function, mechanism, service, or solution, and the assurance (or
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confidence) that is implemented and functioning correctly to
support the level of concern assigned to a particular information
system.
$ Lightweight Directory Access Protocol (LDAP)
(I) An Internet client-server protocol (RFC 3377) that supports
basic use of the X.500 Directory (or other directory servers)
without incurring the resource requirements of the full Directory
Access Protocol (DAP).
Tutorial: Designed for simple management and browser applications
that provide simple read/write interactive directory service.
Supports both simple authentication and strong authentication of
the client to the directory server.
$ link
1a. (I) A communication facility or physical medium that can
sustain data communications between multiple network nodes, in the
protocol layer immediately below IP. [R3573]
1b. (I) /subnetwork/ A communication channel connecting subnetwork
relays (especially one between two packet switches) that is
implemented at OSIRM layer 2. (See: link encryption.)
Tutorial: The relay computers assume that links are logically
passive. If a computer at one end of a link sends a sequence of
bits, the sequence simply arrives at the other end after a finite
time, although some bits may have been changed either accidentally
(errors) or by active wiretapping.
2. (I) /World Wide Web/ See: hyperlink.
$ link encryption
(I) Stepwise (link-by-link) protection of data that flows between
two points in a network, provided by encrypting data separately on
each network link, i.e., by encrypting data when it leaves a host
or subnetwork relay and decrypting when it arrives at the next
host or relay. Each link may use a different key or even a
different algorithm. [R1455] (Compare: end-to-end encryption.)
$ logic bomb
(I) Malicious logic that activates when specified conditions are
met. Usually intended to cause denial of service or otherwise
damage system resources. (See: Trojan horse, virus, worm.)
$ login
(I) The act by which a system entity establishes a session in
which the entity can use system resources. (See: principal,
session.)
Usage: Usually understood to be accomplished by providing a user
name and password to an access control system that authenticates
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the user, but sometimes refers to establishing a connection with a
server when no authentication or specific authorization is
involved.
Derivation: Refers to "log" file", a security audit trail that
records (a) security events, such as the beginning of a session,
and (b) the names of the system entities that initiate events.
$ long title
(O) /U.S. Government/ "Descriptive title of [an item of COMSEC
material]." [C4009] (Compare: short title.)
$ low probability of detection
(I) Result of TRANSEC measures used to hide or disguise a
communication.
$ low probability of intercept
(I) Result of TRANSEC measures used to prevent interception of a
communication.
$ LOTOS
(N) See: Language of Temporal Ordering Specification.
$ MAC
(N) See: mandatory access control, Message Authentication Code.
Deprecated Usage: This abbreviation is ambiguous; therefore, ISDs
that use it SHOULD state a definition for it.
$ magnetic remanence
(N) Magnetic representation of residual information remaining on a
magnetic medium after the medium has been cleared. [NCS25] (See:
clear, degauss, purge.)
$ maintenance hook
(N) "Special instructions (trapdoors) in software allowing easy
maintenance and additional feature development. Since maintenance
hooks frequently allow entry into the code without the usual
checks, they are a serious security risk if they are not removed
prior to live implementation." [C4009] (See: back door.)
$ malicious logic
(I) Hardware, software, or firmware that is intentionally included
or inserted in a system for a harmful purpose. (See: logic bomb,
Trojan horse, spyware, virus, worm. Compare: (secondary
definitions under) corruption, incapacitation, masquerade, and
misuse.)
$ malware
(D) A contraction of "malicious software". (See: malicious logic.)
Deprecated Term: ISDs SHOULD NOT use this term; it is not listed
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in most dictionaries and could confuse international readers.
$ MAN
(I) metropolitan area network.
$ man-in-the-middle attack
(I) A form of active wiretapping attack in which the attacker
intercepts and selectively modifies communicated data in order to
masquerade as one or more of the entities involved in a
communication association. (See: hijack attack, piggyback attack.)
Tutorial: For example, suppose Alice and Bob try to establish a
session key by using the Diffie-Hellman algorithm without data
origin authentication service. A "man in the middle" could (a)
block direct communication between Alice and Bob and then (b)
masquerade as Alice sending data to Bob, (c) masquerade as Bob
sending data to Alice, (d) establish separate session keys with
each of them, and (e) function as a clandestine proxy server
between them in order to capture or modify sensitive information
that Alice and Bob think they are sending only to each other.
$ manager
(I) A person who controls the service configuration of a system or
the functional privileges of operators and other users.
$ mandatory access control
1. (I) An access control service that enforces a security policy
based on comparing (a) security labels, which indicate how
sensitive or critical system resources are, with (b) security
clearances, which indicate that system entities are eligible to
access certain resources. (See: discretionary access control, MAC,
rule-based security policy.)
Derivation: This kind of access control is called "mandatory"
because an entity that has clearance to access a resource is not
permitted, just by its own volition, to enable another entity to
access that resource.
2. (O) "A means of restricting access to objects based on the
sensitivity (as represented by a label) of the information
contained in the objects and the formal authorization (i.e.,
clearance) of subjects to access information of such sensitivity."
[DoD1]
$ manipulation detection code
(D) Synonym for "checksum".
Deprecated Term: ISDs SHOULD NOT use this term as a synonym for
"checksum"; the word "manipulation" implies protection against
active attacks, which an ordinary checksum might not provide.
Instead, if such protection is intended, use "protected checksum"
or some particular type thereof, depending on which is meant. If
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such protection is not intended, use "error detection code" or
some specific type of checksum that is not protected.
$ marking
See: time stamp, security marking.
$ Martian
(D) A packet that arrives unexpectedly at the wrong address or on
the wrong network because of incorrect routing or because it has a
non-registered or ill-formed IP address.
Deprecated Term: It is likely that other cultures have different
metaphors for this concept. Therefore, to ensure international
understanding, ISDs SHOULD NOT use this term. (See: (Deprecated
Usage under) Green Book.)
$ masquerade
(I) A type of threat action whereby an unauthorized entity gains
access to a system or performs a malicious act by illegitimately
posing as an authorized entity. (See: deception.)
Usage: This type includes the following subtypes:
- "Spoof": Attempt by an unauthorized entity to gain access to a
system by posing as an authorized user.
- "Malicious logic": In context of masquerade, any hardware,
firmware, or software (e.g., Trojan horse) that appears to
perform a useful or desirable function, but actually gains
unauthorized access to system resources or tricks a user into
executing other malicious logic. (See: (main entry for)
malicious logic.)
$ MCA
(O) See: merchant certification authority.
$ MD2
(N) A cryptographic hash [R1319] that produces a 128-bit hash
result, was designed by Ron Rivest, and is similar to MD4 and MD5
but slower.
Derivation: Apparently an abbreviation of "message digest", but
that term is deprecated by this Glossary.
$ MD4
(N) A cryptographic hash [R1320] that produces a 128-bit hash
result and was designed by Ron Rivest. (See: SHA-1, (Derivation
under) MD2.)
$ MD5
(N) A cryptographic hash [R1321] that produces a 128-bit hash
result and was designed by Ron Rivest to be an improved version of
MD4. (See: (Derivation under) MD2.)
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$ merchant
(O) /SET/ "A seller of goods, services, and/or other information
who accepts payment for these items electronically." [SET2] A
merchant may also provide electronic selling services and/or
electronic delivery of items for sale. With SET, the merchant can
offer its cardholders secure electronic interactions, but a
merchant that accepts payment cards is required to have a
relationship with an acquirer. [SET1, SET2]
$ merchant certificate
(O) /SET/ A public-key certificate issued to a merchant. Sometimes
used to refer to a pair of such certificates where one is for
digital signature use and the other is for encryption.
$ merchant certification authority (MCA)
(O) /SET/ A CA that issues digital certificates to merchants and
is operated on behalf of a payment card brand, an acquirer, or
another party according to brand rules. Acquirers verify and
approve requests for merchant certificates prior to issuance by
the MCA. An MCA does not issue a CRL, but does distribute CRLs
issued by root CAs, brand CAs, geopolitical CAs, and payment
gateway CAs. [SET2]
$ mesh PKI
(I) A non-hierarchical PKI architecture in which there are several
trusted CAs rather than a single root. Each certificate user bases
path validations on the public key of one of the trusted CAs,
usually the one that issued that user's own public-key
certificate. Rather than having superior-to-subordinate
relationships between CAs, the relationships are peer-to-peer, and
CAs issue cross-certificates to each other. (Compare: hierarchical
PKI, trust-file PKI.)
$ Message Authentication Code, message authentication code
(N) /capitalized/ A specific ANSI standard for a checksum that is
computed with a keyed hash that is based on DES. [A9009] Also
known as the U.S. Government standard Data Authentication Code.
[FP113] (See: MAC.)
(D) /not capitalized/ Synonym for "error detection code".
Deprecated Term: ISDs SHOULD NOT use the uncapitalized form
"message authentication code"; that form mixes concepts in a
potentially misleading way. Instead, use "checksum", "error
detection code", "hash", "keyed hash", "Message Authentication
Code", or "protected checksum", depending on what is meant. (See:
authentication code.)
In the uncapitalized form, the word "message" is misleading
because it implies that the mechanism is particularly suitable for
or limited to electronic mail (see: Message Handling Systems), the
word "authentication" is misleading because the mechanism
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primarily serves a data integrity function rather than an
authentication function, and the word "code" is misleading because
it implies that either encoding or encryption is involved or that
the term refers to computer software.
$ message digest
(D) Synonym for "hash result". (See: cryptographic hash.)
Deprecated Term: ISDs SHOULD NOT use this term as a synonym for
"hash result"; the term unnecessarily duplicates the meaning of
the other, more general term and mixes concepts in a potentially
misleading way. The word "message" is misleading because it
implies that the mechanism is particularly suitable for or limited
to electronic mail (see: Message Handling Systems).
$ message handling system
(D) A synonym for the Internet electronic mail system.
Deprecated Term: ISDs SHOULD NOT use this term, because it could
be confused with Message Handling System. Instead, use "Internet
electronic mail" or some other, more specific term.
$ Message Handling System
(O) A ITU-T system concept that encompasses the notion of
electronic mail but defines more comprehensive OSI systems and
services that enable users to exchange messages on a store-and-
forward basis. (The ISO equivalent is "Message Oriented Text
Interchange System".) (See: X.400.)
$ message indicator
1. (D) /cryptographic function/ Synonym for "initialization
value".
2. (D) "Sequence of bits transmitted over a communications system
for synchronizing cryptographic equipment." [C4009]
Deprecated Term: ISDs SHOULD NOT use this term as a synonym for
"initialization value"; the term mixes concepts in a potentially
misleading way. The word "message" is misleading because it
suggests that the mechanism is limited to electronic mail. (See:
Message Handling System.)
$ message integrity check
$ message integrity code (MIC)
(D) Synonyms for some form of "checksum".
Deprecated Term: ISDs SHOULD NOT use these terms for any form of
checksum. Instead, use "checksum", "error detection code", "hash",
"keyed hash", "Message Authentication Code", or "protected
checksum", depending on what is meant.
The terms mix concepts in potentially misleading ways. The word
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"message" is misleading because it suggests that the mechanism is
particularly suitable for or limited to electronic mail. The word
"integrity" is misleading because the checksum may be used to
perform a data origin authentication function rather than an
integrity function. The word "code" is misleading because it
suggests either that either encoding or encryption is involved or
that the term refers to computer software.
$ Message Security Protocol (MSP)
(N) A secure message handling protocol [SDNS7] for use with X.400
and Internet mail protocols. Developed by NSA's SDNS program and
used in the U.S. DoD's Defense Message System.
$ meta-data
(I) Descriptive information about a data object; i.e., data about
data, or data labels that describe other data. (See: security
label. Compare: metadata)
Tutorial: Meta-data can serve various management purposes:
- System management: File name, type, size, creation date.
- Application management: Document title, version, author.
- Usage management: Data categories, keywords, classifications.
Meta-data can be associated with a data object in two basic ways:
- Explicitly: Be part of the data object (e.g., a header field of
a data file or packet) or be linked to the object.
- Implicitly: Be associated with the data object because of some
other, explicit attribute of the object.
$ metadata, Metadata(trademark), METADATA(trademark)
(O) A proprietary variant of "meta-data". (See: SPAM(trademark).)
Deprecated Usage: The terms "Metadata" and "METADATA" are claimed
as registered trademarks (numbers 1,409,260 and 2,185,504) owned
by The Metadata Company, originally known as Metadata Information
Partners, a company founded by Jack Myers. To avoid litigation,
this Glossary recommends a hyphenated form, "meta-data".
$ MHS
(N) See: message handling system.
$ MIC
(D) See: message integrity code.
$ MIME
(I) See: Multipurpose Internet Mail Extensions.
$ MIME Object Security Services (MOSS)
(I) An Internet protocol [R1848] that applies end-to-end
encryption and digital signature to MIME message content, using
symmetric cryptography for encryption and asymmetric cryptography
for key distribution and signature. MOSS is based on features and
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specifications of PEM. (See: S/MIME.)
$ Minimum Interoperability Specification for PKI Components (MISPC)
(N) A technical description to provide a basis for interoperation
between PKI components from different vendors; consists primarily
of a profile of certificate and CRL extensions and a set of
transactions for PKI operation. [SP15]
$ misappropriation
(I) A type of threat action whereby an entity assumes unauthorized
logical or physical control of a system resource. (See:
usurpation.)
Usage: This type includes the following subtypes:
- Theft of data: Unauthorized acquisition and use of data
contained in a system.
- Theft of service: Unauthorized use of a system service.
- Theft of functionality: Unauthorized acquisition of actual
hardware, software, or firmware of a system component.
$ MISPC
(N) See: Minimum Interoperability Specification for PKI
Components.
$ MISSI
(N) Multilevel Information System Security Initiative, an NSA
program to encourage development of interoperable, modular
products for constructing secure network information systems in
support of a wide variety of Government missions. (See: MSP, SP3,
SP4.)
$ MISSI user
(O) /MISSI/ A system entity that is the subject of one or more
MISSI X.509 public-key certificates issued under a MISSI
certification hierarchy. (See: personality.)
Tutorial: MISSI users include both end users and the authorities
that issue certificates. A MISSI user is usually a person but may
be a machine or other automated process. Some machines are
required to operate non-stop. To avoid downtime needed to exchange
the FORTEZZA cards of machine operators at shift changes, the
machines may be issued their own cards, as if they were persons.
$ mission
(I) A statement of a (relatively long-term) duty or (relatively
short-term) task that is assigned to an organization or system,
indicates the purpose and objectives of the duty or task, and may
indicate the actions to be taken to achieve it.
$ mission critical
(I) A condition of a system service or other system resource such
that denial of access to, or lack of availability of, the resource
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would jeopardize a system user~Os ability to perform a primary
mission function or would result in other serious consequences.
(Compare: mission essential.)
$ mission essential
(O) /DoD/ Refers to materiel that is authorized and available to
combat, combat support, combat service support, and combat
readiness training forces to accomplish their assigned missions.
[JCSP1] (Compare: mission critical.)
$ misuse
1. (I) The intentional use (by authorized users) of system
resources for other than authorized purposes. Example: An
authorized system administrator creates an unauthorized account
for a friend.
2. (I) A type of threat action that causes a system component to
perform a function or service that is detrimental to system
security. (See: usurpation.)
Usage: This type includes the following subtypes:
- "Tampering": In context of misuse, deliberately altering a
system's logic, data, or control information to cause the
system to perform unauthorized functions or services. (See:
(main entry for) tampering.)
- "Malicious logic": In context of misuse, any hardware,
software, or firmware intentionally introduced into a system to
perform or control execution of an unauthorized function or
service. (See: (main entry for) malicious logic.)
- "Violation of authorizations": Action by an entity that exceeds
the entity's system privileges by executing an unauthorized
function. (See: authorization.)
$ misuse detection
(I) An intrusion detection method that is based on rules that
specify system events, sequences of events, or observable
properties of a system that are believed to be symptomatic of
security incidents. (See: IDS. Compare: anomaly detection.)
$ MLS
(I) See: multilevel secure
$ mobile code
1a. (I) Software that originates from a remote server or is
embedded in a document or other application file, is transmitted
across a network, and is loaded onto and executed on a local
client system.
1b. (O) /U.S. DoD/ "Software obtained from remote systems outside
the enclave boundary, transferred across a network, and then
downloaded and executed on a local system without explicit
installation or execution by the recipient."
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2a. (O) /U.S. DoD/ "Technology that enables the creation of
executable information that can be delivered to an information
system and directly executed on any hardware/software architecture
that has an appropriate host execution environment."
2b. (O) "Programs (e.g., script, macro, or other portable
instruction) that can be shipped unchanged to a heterogeneous
collection of platforms and execute with identical semantics" [SP-
28]. (See: active content.)
Tutorial: Mobile code might be malicious. Using techniques such as
"code signing" and a "sandbox" can reduce the risks of receiving
and executing mobile code.
$ mode
$ mode of operation
1. (I) /encryption/ A technique for enhancing the effect of a
cryptographic algorithm or adapting the algorithm for an
application, such as applying a block cipher to a sequence of data
blocks or a data stream. (See: ECB, CBC, CFB, OFB.)
2. (I) /system operation/ A type of security policy that states
the range of classification levels of information that a system is
permitted to handle and the range of clearances and authorizations
of users who are permitted to access the system. (See: dedicated
security mode, multilevel security mode, partitioned security
mode, system high security mode.)
$ modulus
(I) The defining constant in modular arithmetic, and usually a
part of the public key in asymmetric cryptography that is based on
modular arithmetic. (See: Diffie-Hellman, RSA.)
$ Mondex
(O) A smartcard-based electronic money system that incorporates
cryptography and can be used to make payments via the Internet.
(See: IOTP.)
$ Morris Worm
(I) A worm program that flooded the ARPANET in November, 1988,
causing problems for thousands of hosts. [R1135] (See: worm.)
$ MOSS
(I) See: MIME Object Security Services.
$ MQV
(N) A key-agreement protocol [Mene] that was proposed by A.J.
Menezes, M. Qu, and S.A. Vanstone in 1995 and is based on the
Diffie-Hellman algorithm.
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$ MSP
(N) See: Message Security Protocol.
$ multicast security
See: secure multicast
$ Multics
(N) MULTiplexed Information and Computing Service, an MLS computer
timesharing system designed and implemented during 1965-69 by a
consortium including Massachusetts Institute of Technology,
General Electric, and Bell Laboratories, and later offered
commercially by Honeywell.
Tutorial: Multics was one of the first large, general-purpose,
operating systems to include security as a primary goal from the
inception of the design and development and was rated in TCSEC
Class B2. Its many innovative hardware and software security
mechanisms (e.g., protection ring) were adopted by later systems.
$ multilevel secure (MLS)
(I) Describes an information system that is trusted to contain,
and maintain separation between, resources (particularly stored
data) of different security levels. (Examples: BLACKER, CANEWARE,
KSOS, Multics, SCOMP.)
Usage: Usually understood to mean that the system permits
concurrent access by users who differ in their access
authorizations, while denying users access to resources for which
they lack authorization.
$ multilevel security mode
1. (N) A mode of system operation that allows two or more security
levels of information to be handled concurrently within the same
system when not all users have a clearance or specific access
authorization for all data handled by the system. [DoD2]
Usage: This term was defined in U.S. DoD policy regarding system
accreditation [DoD2], but the term is also used outside the
Defense Department and outside government. This term can be
defined more precisely as follows:
2. (N) A mode of system operation in which all three of the
following statements are true: (a) Some authorized users do not
have a security clearance for all the information handled in the
system. (b) All authorized users have the proper security
clearance and appropriate specific access approval for the
information to which they have access. (c) All authorized users
have a need-to-know only for information to which they have
access. [C4009]
$ Multipurpose Internet Mail Extensions (MIME)
(I) An Internet protocol (RFC 2045) that enhances the basic format
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of Internet electronic mail messages (RFC 822) to be able to use
character sets other than U.S. ASCII for textual headers and text
content, and to carry non-textual and multi-part content. (See:
S/MIME.)
$ mutual suspicion
(I) The state that exists between two interacting system entities
in which neither entity can trust the other to function correctly
with regard to some security requirement.
$ name
(I) Synonym for "identifier".
$ National Computer Security Center (NCSC)
(O) A U.S. DoD organization, housed in NSA, that has
responsibility for encouraging widespread availability of trusted
computer systems throughout the Federal Government. It has
established criteria for, and performed evaluations of, computer
and network systems that have a TCB. (See: Evaluated Products
List, Rainbow Series, TCSEC.)
$ National Information Assurance Partnership (NIAP)
(N) An joint initiative of NIST and NSA to enhance the quality of
commercial products for information security and increase consumer
confidence in those products through objective evaluation and
testing methods.
Tutorial: NIAP is registered, through the U.S. DoD, as a National
Performance Review Reinvention Laboratory. NIAP functions include
the following:
- Developing tests, test methods, and other tools that developers
and testing laboratories may use to improve and evaluate
security products.
- Collaborating with industry and others on research and testing
programs.
- Using the Common Criteria to develop protection profiles and
associated test sets for security products and systems.
- Cooperating with the NIST National Voluntary Laboratory
Accreditation Program to develop a program to accredit private-
sector laboratories for the testing of information security
products using the Common Criteria.
- Working to establish a formal, international mutual recognition
scheme for a Common Criteria-based evaluation.
$ National Institute of Standards and Technology (NIST)
(N) A U.S. Department of Commerce organization that promotes U.S.
economic growth by working with industry to develop and apply
technology, measurements, and standards. Has primary Government
responsibility for INFOSEC standards for unclassified but
sensitive information. (See: ANSI, DES, DSA, DSS, FIPS, NIAP,
NSA.)
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$ National Security Agency (NSA)
(N) A U.S. DoD organization that has primary Government
responsibility for INFOSEC standards for classified information
and for unclassified but sensitive information handled by national
security systems. (See: FORTEZZA, KEA, MISSI, NIAP, NIST,
SKIPJACK.)
$ national security information
(N) /U.S. Government/ Information that has been determined,
pursuant to Executive Order 12958 or any predecessor order, to
require protection against unauthorized disclosure. [C4009]
$ national security system
(O) /U.S. Government/ Any Government-operated information system
for which the function, operation, or use (a) involves
intelligence activities; (b) involves cryptologic activities
related to national security; (c) involves command and control of
military forces; (d) involves equipment that is an integral part
of a weapon or weapon system; or (c) is critical to the direct
fulfillment of military or intelligence missions and does not
include a system that is to be used for routine administrative and
business applications (including payroll, finance, logistics, and
personnel management applications). [Title 40 U.S.C. Section 1552,
Information Technology Management Reform Act of 1996.] (See: type
2 product.)
$ NCSC
(O) See: National Computer Security Center.
$ need to know
(I) The necessity for access to, knowledge of, or possession of
specific information required to carry out official duties.
Tutorial: The need-to-know criterion is used in security
procedures that require a custodian of sensitive information,
prior to disclosing the information to someone else, to establish
that the intended recipient has proper authorization to access the
information.
$ network
(I) An information system comprised of a collection of
interconnected modes. (See: computer network.)
$ Network Layer Security Protocol (NLSP).
(N) An OSI protocol (IS0 11577) for end-to-end encryption services
at the top of OSIRM layer 3. NLSP is derived from SP3 but is more
complex. (Compare: IPsec.)
$ network weaving
(I) A penetration technique in which an intruder avoids detection
and traceback by using multiple linked communication networks to
access and attack a system. [C4009]
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$ NIAP
(N) See: National Information Assurance Partnership.
$ nibble
(D) Half of a byte (i.e., usually, 4 bits).
Deprecated Term: To ensure international understanding, ISDs
SHOULD NOT use this term; instead, state the size of the block
explicitly (e.g., "4-bit block"). (See: (Deprecated Usage under)
Green Book.)
$ NIPRNET
(O) The U.S. DoD~Os common-use Non-Classified Internet Protocol
Router Network; the part of the Internet that is wholly controlled
by the U.S. DoD and is used for official DoD business.
$ NIST
(N) See: National Institute of Standards and Technology.
$ NLSP
(N) See: Network Layer Security Protocol
$ no-lone zone
(I) A room or other space or area to which no person may have
unaccompanied access and that, when occupied, is required to be
occupied by two or more appropriately authorized persons. [C4009]
(See: dual control.)
$ no-PIN ORA (NORA)
(O) /MISSI/ An organizational RA that operates in a mode in which
the ORA performs no card management functions and, therefore, does
not require knowledge of either the SSO PIN or user PIN for an end
user's FORTEZZA PC card.
$ node
(I) A collection of related subsystems located on one or more
computer platforms at a single system site.
$ nonce
(I) A random or non-repeating value that is included in data
exchanged by a protocol, usually for the purpose of guaranteeing
liveness and thus detecting and protecting against replay attacks.
$ non-critical
See: critical.
$ non-repudiation service
1. (I) A security service that provide protection against false
denial of involvement in a communication. (See: repudiation, time
stamp.)
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2. (O) "Assurance [that] the sender of data is provided with proof
of delivery and the recipient is provided with proof of the
sender's identity, so neither can later deny having processed the
data." [NS4009]
Deprecated Definition: ISDs SHOULD NOT use the "O" definition
because it bundles two security services -- non-repudiation with
proof of origin, and non-repudiation with proof of receipt -- that
can be provided independently of each other.
Usage: ISDs SHOULD distinguish between the technical aspects and
the legal aspects of a non-repudiation service:
- "Technical non-repudiation": Refers to the assurance a relying
party has that if a public key is used to validate a digital
signature, that signature had to have been made by the
corresponding private signature key. [SP32]
-"Legal non-repudiation": Refers to how well possession or
control of the private signature key can be established. [SP32]
Tutorial: Non-repudiation service does not prevent an entity from
repudiating a communication. Instead, the service provides
evidence that can be stored and later presented to a third party
to resolve disputes that arise if and when a communication is
repudiated by one of the entities involved.
Ford describes the six phases of a complete non-repudiation
service and uses "critical action" to refer to the act of
communication that is the subject of the service [For94, For97]:
-------- -------- -------- -------- -------- . --------
Phase 1: Phase 2: Phase 3: Phase 4: Phase 5: . Phase 6:
Request Generate Transfer Verify Retain . Resolve
Service Evidence Evidence Evidence Evidence . Dispute
-------- -------- -------- -------- -------- . --------
Service Critical Evidence Evidence Archive . Evidence
Request => Action => Stored => Is => Evidence . Is
Is Made Occurs For Later Tested In Case . Verified
and Use | ^ Critical . ^
Evidence v | Action Is . |
Is +-------------------+ Repudiated . |
Generated |Verifiable Evidence|------> ... . ----+
+-------------------+
Phase / Explanation
-------------------
1. Request service: Before the critical action, the service
requester asks, either implicitly or explicitly, to have
evidence of the action be generated.
2. Generate evidence: When the critical action occurs, evidence is
generated by a process involving the potential repudiator and
possibly also a trusted third party.
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3. Transfer evidence: The evidence is transferred to the requester
or stored by a third party, for later use (if needed.)
4. Verify evidence: The entity that holds the evidence tests it to
be sure that it will suffice if a dispute arises.
5. Retain evidence: The evidence is retained for possible future
retrieval and use.
6. Resolve dispute: In this phase, which occurs only if the
critical action is repudiated, the evidence is retrieved from
storage, presented, and verified to resolve the dispute.
$ non-repudiation with proof of origin
(I) A security service that provides the recipient of data with
evidence that proves the origin of the data, and thus protects the
recipient against an attempt by the originator to falsely deny
sending the data. This service can be viewed as a strong version
of data origin authentication service, in that it proves
authenticity to a third party. (See: non-repudiation service.)
$ non-repudiation with proof of receipt
(I) A security service that provides the originator of data with
evidence that proves the data was received as addressed, and thus
protects the originator against an attempt by the recipient to
falsely deny receiving the data. (See: non-repudiation service.)
$ non-volatile media
(I) Storage media that, once written into, provide stable storage
of information without an external power supply. (Compare:
volatile media, permanent storage.)
$ NORA
(O) See: no-PIN ORA.
$ notarization
(I) Registration of data under the authority or in the care of a
trusted third party, thus making it possible to provide subsequent
assurance of the accuracy of characteristics claimed for the data,
such as content, origin, time of existence, and delivery. [I7498
Part 2] (See: digital notary.)
$ NSA
(N) See: National Security Agency
$ null
(N) /encryption/ "Dummy letter, letter symbol, or code group
inserted into an encrypted message to delay or prevent its
decryption or to complete encrypted groups for transmission or
transmission security purposes." [C4009]
$ NULL encryption algorithm
(I) An algorithm [R2410] that is specified as doing nothing to
transform plaintext data; i.e., a no-op. It originated because ESP
always specifies the use of an encryption algorithm for
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confidentiality. The NULL encryption algorithm is a convenient way
to represent the option of not applying encryption in ESP (or in
any other context where a no-op is needed). (Compare: null.)
$ OAKLEY
(I) A key establishment protocol (proposed for IPsec but
superseded by IKE) based on the Diffie-Hellman algorithm and
designed to be a compatible component of ISAKMP. [R2412]
Tutorial: OAKLEY establishes a shared key with an assigned
identifier and associated authenticated identities for parties;
i.e., OAKLEY provides authentication service to ensure the
entities of each other's identity, even if the Diffie-Hellman
exchange is threatened by active wiretapping. Also, it provides
public-key forward secrecy for the shared key and supports key
updates, incorporation of keys distributed by out-of-band
mechanisms, and user-defined abstract group structures for use
with Diffie-Hellman.
$ object
(I) /formal model/ Trusted computer system modeling usage: A
system component that contains or receives information. (See:
Bell-LaPadula model, trusted computer system.)
$ object identifier (OID)
1. (N) An official, globally unique name for a thing, written as a
sequence of integers (which are formed and assigned as defined in
the ASN.1 standard) and used to reference the thing in abstract
specifications and during negotiation of security services in a
protocol.
2. (O) "A value (distinguishable from all other such values) which
is associated with an object." [X680]
Tutorial: Objects named by OIDs are leaves of the object
identifier tree (which is similar to but different from the X.500
Directory Information Tree). Each arc (i.e., each branch of the
tree) is labeled with a non-negative integer. An OID is the
sequence of integers on the path leading from the root of the tree
to a named object.
The OID tree has three arcs immediately below the root: {0} for
use by ITU-T, {1} for use by ISO, and {2} for use by both jointly.
Below ITU-T are four arcs, where {0 0} is for ITU-T
recommendations. Below {0 0} are 26 arcs, one for each series of
recommendations starting with the letters A to Z, and below these
are arcs for each recommendation. Thus, the OID for ITU-T
Recommendation X.509 is {0 0 24 509}. Below ISO are four arcs,
where {1 0 }is for ISO standards, and below these are arcs for
each ISO standard. Thus, the OID for ISO/IEC 9594-8 (the ISO
number for X.509) is {1 0 9594 8}.
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ANSI registers organization names below the branch {joint-iso-
ccitt(2) country(16) US(840) organization(1) gov(101) csor(3)}.
The NIST CSOR records PKI objects below the branch {joint-iso-itu-
t(2) country(16) us(840) organization (1) gov(101) csor(3)}. The
U.S. DoD registers INFOSEC objects below the branch {joint-iso-
itu-t(2) country(16) us(840) organization(1) gov(101) dod(2)
infosec(1)}.
The IETF's Public-Key Infrastructure (pkix) Working Group
registers PKI objects below the branch {iso(1) identified-
organization(3) dod(6) internet(1) security(5) mechanisms(5)
pkix(7)}. [R2459]
$ object reuse
(N) /COMPUSEC/ Reassignment and reuse of an area of a storage
medium (e.g., random-access memory, floppy disk, magnetic tape)
that once contained sensitive data objects. Before being
reassigned for use by a new subject, the area must erased or, in
some cases, purged. [NCS04]
$ obstruction
(I) A type of threat action that interrupts delivery of system
services by hindering system operations. (See: disruption.)
Tutorial: This type includes the following subtypes:
- "Interference": Disruption of system operations by blocking
communications or user data or control information. (See:
jamming.)
- "Overload": Hindrance of system operation by placing excess
burden on the performance capabilities of a system component.
(See: flooding.)
$ OCSP
(I) See: On-line Certificate Status Protocol.
$ octet
(I) A data unit of eight bits. (Compare: byte.)
Usage: This term is used in networking (especially in OSI
standards) in preference to "byte", because some systems use
"byte" for data storage units of a size other than eight bits.
$ OFB
(N) See: output feedback.
$ off-line attack
(I) See: (secondary definition under) attack.
$ ohnosecond
(D) That minuscule fraction of time in which you realize that your
private key has been compromised.
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Deprecated Usage: This is a joke for English speakers. (See:
(Deprecated Usage under) Green Book.)
$ OID
(N) See: object identifier.
$ On-line Certificate Status Protocol (OCSP)
(I) An Internet protocol [R2560] used by a client to obtain from a
server the validity status and other information concerning a
digital certificate.
Tutorial: In some applications, such as those involving high-value
commercial transactions, it may be necessary either (a) to obtain
certificate revocation status that is more timely than is possible
with CRLs or (b) to obtain other kinds of status information. OCSP
may be used to determine the current revocation status of a
digital certificate, in lieu of or as a supplement to checking
against a periodic CRL. An OCSP client issues a status request to
an OCSP server and suspends acceptance of the certificate in
question until the server provides a response.
$ one-time pad
1. (N) A manual encryption system in the form of a paper pad for
one-time use.
2. (I) An encryption algorithm in which the key is a random
sequence of symbols and each symbol is used for encryption only
one time -- to encrypt only one plaintext symbol to produce only
one ciphertext symbol -- and a copy of the key is used similarly
for decryption.
Tutorial: To ensure one-time use, the copy of the key used for
encryption is destroyed after use, as is the copy used for
decryption. This is the only encryption algorithm that is truly
unbreakable, even given unlimited resources for cryptanalysis
[Schn], but key management costs and synchronization problems make
it impractical except in special situations.
$ one-time password, One-Time Password (OTP)
1. (I) /not capitalized/ A "one-time password" is a simple
authentication technique in which each password is used only once
as authentication information that verifies an identity. This
technique counters the threat of a replay attack that uses
passwords captured by wiretapping.
2. (I) /capitalized/ "One-Time Password" is an Internet protocol
[R1938] that is based on S/KEY and uses a cryptographic hash
function to generate one-time passwords for use as authentication
information in system login and in other processes that need
protection against replay attacks.
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$ one-way encryption
(I) Irreversible transformation of plain text to cipher text, such
that the plain text cannot be recovered from the cipher text by
other than exhaustive procedures even if the cryptographic key is
known. (See: encryption.)
$ one-way function
(I) "A (mathematical) function, f, which is easy to compute, but
which for a general value y in the range, it is computationally
difficult to find a value x in the domain such that f(x) = y.
There may be a few values of y for which finding x is not
computationally difficult." [X509]
Deprecated Usage: ISDs SHOULD NOT use this term as a synonym for
"cryptographic hash".
$ onion routing
(I) A system that can be used to provide both (a) data
confidentiality and (b) traffic-flow confidentiality for network
packets, and also provide (c) anonymity for the source of the
packets.
Tutorial: The source, instead of sending a packet directly to the
intended destination, sends it to an "onion routing proxy" that
builds an anonymous connection through several other "onion
routers" to the destination. The proxy defines a route through the
"onion routing network" by encapsulating the original payload in a
layered data packet called an "onion", in which each layer defines
the next hop in the route and each layer is also encrypted. Along
the route, each onion router that receives the onion peels off one
layer; decrypts that layer and reads from it the address of the
next onion router on the route; pads the remaining onion to some
constant size; and sends the padded onion to that next router.
$ open security environment
(O) /U.S. DoD/ A system environment that meets at least one of the
following two conditions: (a) Application developers (including
maintainers) do not have sufficient clearance or authorization to
provide an acceptable presumption that they have not introduced
malicious logic. (b) Configuration control does not provide
sufficient assurance that applications and the equipment are
protected against the introduction of malicious logic prior to and
during the operation of system applications. [NCS04] (See: (first
law under) Courtney's laws. Compare: closed security environment.)
$ open storage
(N) /U.S. Government/ "Storage of classified information within an
accredited facility, but not in General Services Administration
approved secure containers, while the facility is unoccupied by
authorized personnel." [C4009]
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$ Open Systems Interconnection (OSI) Reference Model (OSIRM)
(N) A joint ISO/ITU-T standard [I7498 Part 1] for a seven-layer,
architectural communication framework for interconnection of
computers in networks.
Tutorial: OSIRM-based standards include communication protocols
that are mostly incompatible with the IPS, but also include
security models, such as X.509, that are used in the Internet.
The OSIRM layers, from highest to lowest, are (7) Application, (6)
Presentation, (5) Session, (4) Transport, (3) Network, (2) Data
Link, and (1) Physical.
Usage: In other Glossary entries, OSIRM layers are referred to by
number to avoid confusing them with IPS layers, which are referred
to by name.
Some unknown person described how the OSIRM layers correspond to
the seven deadly sins:
7. Wrath: Application is always angry at the mess it sees below
itself. (Hey! Who is it to be pointing fingers?)
6. Sloth: Presentation is too lazy to do anything productive by
itself.
5. Lust: Session is always craving and demanding what truly
belongs to Application's functionality.
4. Avarice: Transport wants all of the end-to-end functionality.
(Of course, it deserves it, but life isn't fair.)
3. Gluttony: (Connection-Oriented) Network is overweight and
overbearing after trying too often to eat Transport's lunch.
2. Envy: Poor Data Link is always starved for attention. (With
Asynchronous Transfer Mode, maybe now it is feeling less
neglected.)
1. Pride: Physical has managed to avoid much of the controversy,
and nearly all of the embarrassment, suffered by the others.
John G. Fletcher described how the OSIRM layers correspond to Snow
White's dwarf friends:
7. Doc: Application acts as if it is in charge, but sometimes
muddles its syntax.
6. Sleepy: Presentation is indolent, being guilty of the sin of
Sloth.
5. Dopey: Session is confused because its charter is not very
clear.
4. Grumpy: Transport is irritated because Network has encroached
on Transport's turf.
3. Happy: Network smiles for the same reason that Transport is
irritated.
2. Sneezy: Data Link makes loud noises in the hope of attracting
attention.
1. Bashful: Physical quietly does its work, unnoticed by the
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others.
$ operational integrity
(I) Synonym for "system integrity"; this synonym emphasizes the
actual performance of system functions rather than just the
ability to perform them.
$ operational security
(D) Synonym for "administrative security". (Compare: OPSEC.)
Deprecated Definition: ISDs SHOULD NOT use this term as a synonym
for "administrative security". Any type of security may affect
system operations; therefore, the term may be misleading. Instead,
use "administrative security", "communication security", "computer
security", "emanations security", "personnel security", "physical
security", or whatever specific type is meant. (Compare: OPSEC.
See: security architecture.)
$ operations security (OPSEC)
(I) A process to identify, control, and protect evidence of the
planning and execution of sensitive activities and operations, and
thereby prevent potential adversaries from gaining knowledge of
capabilities and intentions. (See: communications cover. Compare:
operational security.)
$ operator
(I) A person who has been authorized to direct selected functions
of a system. (Compare: manager.)
Usage: A system operator may or may not be treated as a "user";
therefore, ISDs that use this term SHOULD state a definition for
it.
$ OPSEC
(I) See: operations security.
$ ORA
See: organizational registration authority.
$ Orange Book
(D) Synonym for "Trusted Computer System Evaluation Criteria"
[CSC001, DoD1].
Deprecated Usage: ISDs SHOULD NOT use this term as a synonym for
"Trusted Computer System Evaluation Criteria" [CSC001, DoD1].
Instead, use the full, proper name of the document or, in
subsequent references, the abbreviation "TCSEC". (See: (Deprecated
Usage under) Green Book.)
$ organizational certificate
(I) A X.509 certificate in which the "subject" field contains the
name of an institution or set (e.g., a business, government,
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school, labor union, club, ethnic group, nationality, system, or
group of individuals playing the same role), rather than the name
of an individual person or device. (Compare: persona certificate,
role certificate.)
Tutorial: Such a certificate might be issued for one of the
following purposes:
- To enable an individual to prove membership in the
organization.
- To enable an individual to represent the organization, i.e., to
act in its name and with it powers or permissions.
(O) /MISSI/ A type of MISSI X.509 public-key certificate that is
issued to support organizational message handling for the U.S.
DoD's Defense Message System.
$ organizational registration authority (ORA)
1. (I) /PKI/ An RA for an organization.
2. (O) /MISSI/ An end entity that (a) assists a PCA, CA, or SCA to
register other end entities, by gathering, verifying, and entering
data and forwarding it to the signing authority and (b) may also
assist with card management functions. An ORA is a local
administrative authority, and the term refers both to the role and
to the person who plays that role. An ORA does not sign
certificates, CRLs, or CKLs. (See: no-PIN ORA, SSO-PIN ORA, user-
PIN ORA.)
$ origin authentication
Deprecated Term: ISDs SHOULD NOT use this term; it looks like
careless use of the internationally standardized term "data origin
authentication", and also could be confused with "peer entity
authentication." (See: authentication.)
$ origin authenticity
Deprecated Term: ISDs SHOULD NOT use this term; it looks like
careless use of the internationally standardized term "data origin
authentication", and mixes concepts in a potentially misleading
way. (See: authenticity, origin authentication.)
$ OSI
$ OSIRM
(N) See: Open Systems Interconnection Reference Model.
$ OTAR
(N) See: over-the-air rekeying.
$ OTP
(I) See: One-Time Password.
$ out of band
1a. (I) Transfer of information using a channel that is outside
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(i.e., separate from) the main or normal channel.
1b. (I) Transfer of information using a means or method that
differs from the main or normal method of communication.(See:
covert channel.)
Tutorial: Out-of-band mechanisms are often used to distribute
shared secrets (e.g., a symmetric key) or other sensitive
information items (e.g., a root key) that are needed to initialize
or otherwise enable the operation of cryptography or other
security mechanisms. Example: Using postal mail to distribute
printed or magnetic media containing symmetric cryptographic keys
for use in Internet encryption devices. (See: key distribution.)
$ output feedback (OFB)
(N) A block cipher mode [FP081] that modifies ECB mode to operate
on plaintext segments of variable length less than or equal to the
block length.
Tutorial: This mode operates by directly using the algorithm's
previously generated output block as the algorithm's next input
block (i.e., by "feeding back" the output block) and combining
(exclusive OR-ing) the output block with the next plaintext
segment (of block length or less) to form the next ciphertext
segment.
$ outside attack
(I) See: (secondary definition under) attack. Compare: outsider.)
$ outsider
(I) A user (usually a person) that accesses a system from a
position that is outside the system's security perimeter.
(Compare: authorized user, insider, unauthorized user.)
Tutorial: The actions performed by an outsider in accessing the
system may be either authorized or unauthorized; i.e., an outsider
may act either as an authorized user or as an unauthorized user.
$ over-the-air rekeying (OTAR)
(N) Changing a key in a remote cryptographic device by sending a
new key directly to the device via a channel that the device is
protecting. [C4009]
$ overload
(I) See: (secondary definition under) obstruction.
$ P1363
(N) See: IEEE P1363.
$ PAA
(O) See: policy approving authority.
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$ package
(N) /Common Criteria/ A reusable set of either functional or
assurance components (e.g. an EAL), combined in a single unit to
satisfy a set of identified security objectives.
Tutorial: A package is a combination of security requirement
components and is intended to be reusable in the construction of
either more complex packages or protection profiles and security
targets. A package expresses a set of either functional or
assurance requirements that meet some particular need, expressed
as a set of security objectives. Example: The seven EALs defined
in Part 3 of the Common Criteria are predefined assurance
packages.
$ packet filter
(I) See: (secondary definition under) filtering router.
$ packet monkey
(D) Someone who floods a system with packets, creating a denial-
of-service condition for the system's users.(See: cracker.)
$ pagejacking
(D) A contraction of "Web page hijacking". A masquerade attack in
which the attacker copies (steals) a home page or other material
from the target server, rehosts the page on a server the attacker
controls, and causes the rehosted page to be indexed by the major
Web search services, thereby diverting browsers from the target
server to the attacker's server.
Deprecated Term: ISDs SHOULD NOT use this contraction. The term is
not listed in most dictionaries and could confuse international
readers. (See: (Deprecated Usage under) Green Book.)
$ PAN
(O) See: primary account number.
$ PAP
(I) See: Password Authentication Protocol.
$ parity bit
(I) A checksum that is computed on a block of bits by computing
the binary sum of the individual bits in the block and then
discarding all but the low-order bit of the sum.
$ partitioned security mode
(N) A mode of operation of an information system, wherein all
users have the clearance, but not necessarily formal access
authorization and need-to-know, for all data handled by the
system. This mode is defined in U.S. DoD policy regarding system
accreditation. [DoD2]
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$ PASS
(N) See: personnel authentication system string.
$ passive attack
(I) See: (secondary definition under) attack.
$ passive wiretapping
(I) A wiretapping attack that attempts only to observer
communication flow and gain knowledge of the data it contains, but
does not alter or otherwise affect that flow. (See: wiretapping.
Compare: passive attack, active wiretapping.)
$ password
(I) A secret data value, usually a character string, that is
presented to a system by a user to authenticate the user's
identity. (See: challenge-response, PIN, simple authentication.)
(O) "A character string used to authenticate an identity." [CSC2]
(O) "A string of characters (letters, numbers, and other symbols)
used to authenticate an identity or to verify access
authorization." [FP140]
(O) "A secret that a claimant memorizes and uses to authenticate
his or her identity. Passwords are typically character strings."
[SP63]
Tutorial: A password is usually paired with a user identifier that
is explicit in the authentication process, although in some cases
the identifier may be implicit. A password is usually verified by
matching it to a stored value held by the access control system
for that identifier.
Using a password as authentication information is based on
assuming that the password is known only by the system entity for
which the identity is being authenticated. Therefore, in a network
environment where wiretapping is possible, simple authentication
that relies on transmission of static (i.e., repetitively used)
passwords in cleartext form is inadequate. (See: one-time
password, strong authentication.)
$ Password Authentication Protocol (PAP)
(I) A simple authentication mechanism in PPP. In PAP, a user
identifier and password are transmitted in cleartext form. [R1334]
(See: CHAP.)
$ password sniffing
(I) Passive wiretapping, usually on a LAN, to gain knowledge of
passwords. (See: (Deprecated Usage note under) sniffing.)
$ path discovery
(I) For a digital certificate, the process of finding a set of
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public-key certificates that comprise a certification path from a
trusted key to that specific certificate.
$ path validation
(I) The process of validating (a) all of the digital certificates
in a certification path and (b) the required relationships between
those certificates, thus validating the contents of the last
certificate on the path. (See: certificate validation.)
Tutorial: To promote interoperable PKI applications in the
Internet, RFC 3280 specifies a detailed algorithm for validation
of a certification path.
$ payment card
(N) /SET/ Collectively refers "to credit cards, debit cards,
charge cards, and bank cards issued by a financial institution and
which reflects a relationship between the cardholder and the
financial institution." [SET2]
$ payment gateway
(O) /SET/ A system operated by an acquirer, or a third party
designated by an acquirer, for the purpose of providing electronic
commerce services to the merchants in support of the acquirer, and
which interfaces to the acquirer to support the authorization,
capture, and processing of merchant payment messages, including
payment instructions from cardholders. [SET1, SET2]
$ payment gateway certification authority (SET PCA)
(O) /SET/ A CA that issues digital certificates to payment
gateways and is operated on behalf of a payment card brand, an
acquirer, or another party according to brand rules. A SET PCA
issues a CRL for compromised payment gateway certificates. [SET2]
(See: PCA.)
$ PC card
(N) A type of credit card-sized, plug-in peripheral device that
was originally developed to provide memory expansion for portable
computers, but is also used for other kinds of functional
expansion. (See: FORTEZZA, PCMCIA.)
Tutorial: The international PC Card Standard defines a non-
proprietary form factor in three sizes -- Types I, II and III --
each of which have a 68-pin interface between the card and the
socket into which it plugs. All three types have the same length
and width, roughly the size of a credit card, but differ in their
thickness from 3.3 to 10.5 mm. Examples include storage modules,
modems, device interface adapters, and cryptographic modules.
$ PCA
Deprecated Term: ISDs SHOULD NOT use this acronym without a
qualifying adjective; that would be ambiguous. (See: Internet
policy certification authority, (MISSI) policy creation authority,
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(SET) payment gateway certification authority.)
$ PCMCIA
(N) Personal Computer Memory Card International Association, a
group of manufacturers, developers, and vendors, founded in 1989
to standardize plug-in peripheral memory cards for personal
computers and now extended to deal with any technology that works
in the PC Card form factor. (See: PC card.)
$ PDS
(N) See: protective distribution system.
$ peer entity authentication
(I) "The corroboration that a peer entity in an association is the
one claimed." [I7498 Part 2] (See: authentication.)
$ peer entity authentication service
(I) A security service that verifies an identity claimed by or for
a system entity in an association. (See: authentication,
authentication service.)
Tutorial: This service is used at the establishment of, or at
times during, an association to confirm the identity of one entity
to another, thus protecting against a masquerade by the first
entity. However, unlike data origin authentication service, this
service requires an association to exist between the two entities,
and the corroboration provided by the service is valid only at the
current time that the service is provided. (See: ("relationship
between data integrity service and authentication services" under)
data integrity service).
$ PEM
(I) See: Privacy Enhanced Mail.
$ penetrate
1a. Circumvent a system's security protections. (See: attack,
break, violation.)
1b. (I) Successfully and repeatedly gain unauthorized access to a
protected system resource. [Huff]
$ penetration test
(I) A system test, often part of system certification, in which
evaluators attempt to circumvent the security features of a
system. [NCS04, SP42] (See: tiger team.)
Tutorial: Penetration testing evaluates the relative vulnerability
of a system to attacks and identifies methods of gaining access to
a system by using tools and techniques that are available to
adversaries. Testing may be performed under various constraints
and conditions, including a specified level of knowledge of the
system design and implementation. For a TCSEC evaluation, testers
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are assumed to have all system design and implementation
documentation, including source code, manuals, and circuit
diagrams, and to work under no greater constraints than those
applied to ordinary users.
$ perfect forward secrecy
(I) See: (usage discussion under) public-key forward secrecy.
$ perimeter
See: security perimeter.
$ periods processing
(I) A mode of system operation in which information of different
sensitivities is processed at distinctly different times by the
same system, with the system being properly purged or sanitized
between periods. (See: color change.)
Tutorial: The security mode of operation and maximum
classification of data handled by the system is established for an
interval of time and then is changed for the following interval of
time. A period extends from the secure initialization of the
system to the completion of any purging of sensitive data handled
by the system during the period.
$ permanent storage
(I) Non-volatile media that, once written into, can never be
completely erased.
$ permission
1a. (I) A synonym for "authorization". (Compare: privilege.)
1b. (I) An authorization or set of authorizations to perform
security-relevant functions in the context of role-based access
control. [ANSI]
Tutorial: A permission is a positively-stated authorization for
access that (a) can be associated with one or more roles and (b)
enables a user in a role to access a specified set of system
resources by causing a specific set of system actions to be
performed on the resources.
$ persona certificate
(I) An X.509 certificate issued to a system entity that wishes to
use a persona to conceal its true identity when using PEM or other
Internet services that depend on PKI support. (See: anonymity.)
[R1422]
Tutorial: PEM designers intended that (a) a CA issuing persona
certificates would explicitly not be vouching for the identity of
the system entity to whom the certificate is issued, (b) such
certificates would be issued only by CAs subordinate to a policy
CA having a policy stating that purpose (i.e., that would warn
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relying parties that the "subject" field DN represented only a
persona and not a true, vetted user identity), and (c) the CA
would not need to maintain records binding the true identity of
the subject to the certificate.
However, the PEM designers also intended that a CA issuing persona
certificates would establish procedures (d) to enable "the holder
of a PERSONA certificate to request that his certificate be
revoked" and (e) to ensure that it did not issue the same subject
DN to multiple users. The latter condition implies that a persona
certificate is not an organizational certificate unless the
organization has just one member or representative.
$ personal identification number (PIN)
1a. (I) A character string used as a password to gain access to a
system resource. (See: authentication information.)
1b. (O) An alphanumeric code or password used to authenticate an
identity.
Tutorial: Despite the words "identification" and "number", a PIN
seldom serves as a user identifier, and a PIN's characters are not
necessarily all numeric. Retail banking applications use 4-digit
numeric user PINs, but the FORTEZZA PC card uses 12-character
alphanumeric SSO PINs.
Thus, a better name for this concept would have been "personnel
authentication system string" (PASS), in which case an
alphanumeric character string for this purpose would have been
called, obviously, a "PASSword".
$ personality
1. (I) Synonym for "principal".
2. (O) /MISSI/ A set of MISSI X.509 public-key certificates that
have the same subject DN, together with their associated private
keys and usage specifications, that is stored on a FORTEZZA PC
card to support a role played by the card's user.
Tutorial: When a card's user selects a personality to use in a
FORTEZZA-aware application, the data determines behavior traits
(the personality) of the application. A card's user may have
multiple personalities on the card. Each has a "personality
label", a user-friendly character string that applications can
display to the user for selecting or changing the personality to
be used. For example, a military user's card might contain three
personalities: GENERAL HALFTRACK, COMMANDER FORT SWAMPY, and NEW
YEAR'S EVE PARTY CHAIRMAN. Each personality includes one or more
certificates of different types (such as DSA versus RSA), for
different purposes (such as digital signature versus encryption),
or with different authorizations.
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$ personnel authentication system string (PASS)
(N) See: (Tutorial under) personal identification number.
$ personnel security
(I) Procedures to ensure that persons who access a system have
proper clearance, authorization, and need-to-know as required by
the system's security policy.
$ PGP(trademark)
(O) See: Pretty Good Privacy(trademark).
$ Photuris
(I) A UDP-based, key establishment protocol for session keys,
designed for use with the IPsec protocols AH and ESP. Superseded
by IKE.
$ phreaking
(D) A contraction of "telephone breaking". An attack on or
penetration of a telephone system or, by extension, any other
communication or information system. [Raym]
Deprecated Term: ISDs SHOULD NOT use this contraction; it is not
listed in most dictionaries and could confuse international
readers.
$ physical security
(I) Tangible means of preventing unauthorized physical access to a
system. Examples: Fences, walls, and other barriers; locks, safes,
and vaults; dogs and armed guards; sensors and alarm bells.
[FP031, R1455]
$ piggyback attack
(I) A form of active wiretapping in which the attacker gains
access to a system via intervals of inactivity in another user's
legitimate communication connection. Sometimes called a "between-
the-lines" attack. (See: hijack attack, man-in-the-middle attack.)
Deprecated Usage: This term could confuse international readers;
therefore, ISDs that use it SHOULD state a definition for it.
$ PIN
(I) See: personal identification number.
$ ping of death
(D) A denial-of-service attack that sends an improperly large ICMP
echo request packet (a "ping") with the intent of causing the
destination system to fail. (See: ping sweep, teardrop.)
Deprecated Term: ISDs SHOULD NOT use this term; instead, use "ping
packet overflow attack" or some other term that is specific with
regard to the attack mechanism.
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Tutorial: This attack seeks to exploit an implementation
vulnerability. The IP specification requires hosts to be prepared
to accept datagrams of up to 576 octets, but also permits IP
datagrams to be up to 65,535 octets long. If an IP implementation
does not properly handle very long IP packets, the ping packet may
overflow the input buffer and cause a fatal system error.
$ ping sweep
(I) An attack that sends ICMP echo requests ("pings") to a range
of IP addresses, with the goal of finding hosts that can be probed
for vulnerabilities. (See: ping of death. Compare: port scan.)
$ PKCS
(N) See: Public-Key Cryptography Standards.
$ PKCS #5
(N) A standard [PKC05, R2898] from the PKCS series; defines a
method for encrypting an octet string with a secret key derived
from a password.
Tutorial: Although the method can be used for arbitrary octet
strings, its intended primary application in public-key
cryptography is for encrypting private keys when transferring them
from one computer system to another, as described in PKCS #8.
$ PKCS #7
(N) A standard [PKC07, R2315] from the PKCS series; defines a
syntax for data that may have cryptography applied to it, such as
for digital signatures and digital envelopes. (See: CMS.)
$ PKCS #10
(N) A standard [PKC10] from the PKCS series; defines a syntax for
requests for public-key certificates. (See: certification
request.)
Tutorial: A PKCS #10 request contains a DN and a public key, and
may contain other attributes, and is signed by the entity making
the request. The request is sent to a CA, who converts it to an
X.509 public-key certificate (or some other form), and returns it,
possibly in PKCS #7 format.
$ PKCS #11
(N) A standard [PKC11] from the PKCS series; defines a software
CAPI called Cryptoki (an abbreviation of "cryptographic token
interface", pronounced "CRYPTO-key") for devices that hold
cryptographic information and perform cryptographic functions.
$ PKI
(I) See: public-key infrastructure.
$ PKIX
1a. (I) A contraction of "Public-Key Infrastructure (X.509)", the
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name of the IETF working group that is specifying an architecture
[R3280] and set of protocols [R2510] to provide X.509-based PKI
services for the Internet.
1b. (I) A collective name for that Internet PKI architecture and
associated set of protocols.
Tutorial: The goal of PKIX is to facilitate the use of X.509
public-key certificates in multiple Internet applications and to
promote interoperability between different implementations that
use those certificates. The resulting PKI is intended to provide a
framework that supports a range of trust and hierarchy
environments and a range of usage environments. PKIX specifies (a)
profiles of the v3 X.509 public-key certificate standards and the
v2 X.509 CRL standards for the Internet, (b) operational protocols
used by relying parties to obtain information such as certificates
or certificate status, (c) management protocols used by system
entities to exchange information needed for proper management of
the PKI, and (d) information about certificate policies and CPSs,
covering the areas of PKI security not directly addressed in the
rest of PKIX.
$ PKIX private extension
(I) PKIX defines an private extension to identify an on-line
verification service supporting the issuing CA.
$ plain text
(I) /noun/ Data that is input to and transformed by an encryption
process, or that is output from a decryption process. (Compare:
plaintext.)
Tutorial: Usually, the plain text that is the input to an
encryption operation is clear text. But in some cases, the input
is cipher text that was output from another encryption operation.
(See: superencryption.)
$ plaintext
1a. (I) /adjective/ Referring to plain text. (See: plain text.)
1b. (D) /noun/ A synonym for plain text.
Deprecated Usage: To avoid ambiguity, ISDs SHOULD differentiate
between the noun phrase "plain text" and adjective "plaintext".
$ PLI
(I) See: Private Line Interface.
$ Point-to-Point Protocol (PPP)
(I) An Internet Standard protocol (RFC 1661) for encapsulation and
full-duplex transportation of protocol data packets in OSIRM layer
3 over an OSIRM layer 2 link between two peers, and for
multiplexing different layer 3 protocols over the same link.
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Includes optional negotiation to select and use a peer entity
authentication protocol to authenticate the peers to each other
before they exchange layer 3 data. (See: CHAP, EAP, PAP.)
$ Point-to-Point Tunneling Protocol (PPTP)
(I) An Internet client-server protocol (RFC 2637) (originally
developed by Ascend and Microsoft) that enables a dial-up user to
create a virtual extension of the dial-up link across a network by
tunneling PPP over IP. (See: L2TP.)
Tutorial: PPP can encapsulate any IPS network layer protocol or
OSIRM layer 3 protocol. Therefore, PPTP does not specify security
services; it depends on protocols above and below it to provide
any needed security. PPTP makes it possible to divorce the
location of the initial dial-up server (i.e., the PPTP Access
Concentrator, the client, which runs on a special-purpose host)
from the location at which the dial-up protocol (PPP) connection
is terminated and access to the network is provided (i.e., at the
PPTP Network Server, which runs on a general-purpose host).
$ policy
1a. (I) A plan or course of action that is stated for a system or
organization and is intended to affect and direct the decisions
and deeds of that entity's components or members. (See: security
policy.)
1b. (O) A definite goal, course, or method of action to guide and
determine present and future decisions, that is implemented or
executed within a particular context, such as within a business
unit. [R3198]
Deprecated Usage: ISDs SHOULD NOT use "policy" as an abbreviation
for either "security policy" or "certificate policy". Instead, to
avoid misunderstanding, use a fully qualified term, at least at
the point of first usage.
Tutorial: The introduction of new technology to replace
traditional systems can result in new systems being deployed
without adequate policy definition and before the implications of
the new technology are fully understand. In some cases, it can be
difficult to establish policies for new technology before the
technology has been operationally tested and evaluated. Thus,
policy changes tend to lag behind technological changes, such that
either old policies impede the technical innovation, or the new
technology is deployed without adequate policies to govern its
use.
When new technology changes the ways that things are done, new
"procedures" must be defined to establish operational guidelines
for using the technology and achieving satisfactory results, and
new "practices" must be established for managing new systems and
monitoring results. Practices and procedures are more directly
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coupled to actual systems and business operations than are
polices, which tend to be more abstract.
- "Practices" define how a system is to be managed and what
controls are in place to monitor the system and detect abnormal
behavior or quality problems. Practices are established to
ensure that a system is managed in compliance with stated
policies. System audits are primarily concerned with whether or
not practices are being followed. Auditors evaluate the
controls to make sure they conform to accepted industry
standards, and then confirm that controls are in place and that
control measurements are being gathered. Audit trails are
examples of control measurements that are recorded as part of
system operations.
- "Procedures" define how a system is operated, and relate
closely to issues of what technology is used, who the operators
are, and how the system is deployed physically. Procedures
define both normal and abnormal operating circumstances.
For every control defined by a practice statement, there should be
corresponding procedures to implement the control and provide
ongoing measurement of the control parameters. Conversely,
procedures require management practices to insure consistent and
correct operational behavior.
$ policy approving authority (PAA)
(O) /MISSI/ The top-level signing authority of a MISSI
certification hierarchy. The term refers both to that
authoritative office or role and to the person who plays that
role. (See: root registry.)
Tutorial: A PAA registers MISSI PCAs and signs their X.509 public-
key certificates. A PAA issues CRLs but does not issue a CKL. A
PAA may issue cross-certificates to other PAAs.
$ policy certification authority (Internet PCA)
(I) An X.509-compliant CA at the second level of the Internet
certification hierarchy, under the IPRA. Each PCA operates in
accordance with its published security policy (see: certificate
policy, CPS) and within constraints established by the IPRA for
all PCAs. [R1422]. (See: policy creation authority.)
$ policy creation authority (MISSI PCA)
(O) /MISSI/ The second level of a MISSI certification hierarchy;
the administrative root of a security policy domain of MISSI users
and other, subsidiary authorities. The term refers both to that
authoritative office or role and to the person who fills that
office. (See: policy certification authority.)
Tutorial: A MISSI PCA's certificate is issued by a PAA. The PCA
registers the CAs in its domain, defines their configurations, and
issues their X.509 public-key certificates. (The PCA may also
issue certificates for SCAs, ORAs, and other end entities, but a
PCA does not usually do this.) The PCA periodically issues CRLs
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and CKLs for its domain.
$ Policy Management Authority
(N) Canadian usage: An organization responsible for PKI oversight
and policy management in the Government of Canada.
$ policy mapping
(I) "Recognizing that, when a CA in one domain certifies a CA in
another domain, a particular certificate policy in the second
domain may be considered by the authority of the first domain to
be equivalent (but not necessarily identical in all respects) to a
particular certificate policy in the first domain." [X509]
$ POP3
(I) See: Post Office Protocol, version 3.
$ POP3 APOP
(I) A POP3 command (i.e., a transaction type, or a protocol-
within-a-protocol) by which a POP3 client optionally uses a keyed
hash (based on MD5) to authenticate itself to a POP3 server and,
depending on the server implementation, to protect against replay
attacks. (See: CRAM, POP3 AUTH, IMAP4 AUTHENTICATE.)
Tutorial: The server includes a unique timestamp in its greeting
to the client. The subsequent APOP command sent by the client to
the server contains the client's name and the hash result of
applying MD5 to a string formed from both the timestamp and a
shared secret that is known only to the client and the server.
APOP was designed to provide an alternative to using POP3's USER
and PASS (i.e., password) command pair, in which the client sends
a cleartext password to the server.
$ POP3 AUTH
(I) A POP3 command [R1734] (i.e., a transaction type, or a
protocol-within-a-protocol) by which a POP3 client optionally
proposes a mechanism to a POP3 server to authenticate the client
to the server and provide other security services. (See: POP3
APOP, IMAP4 AUTHENTICATE.)
Tutorial: If the server accepts the proposal, the command is
followed by performing a challenge-response authentication
protocol and, optionally, negotiating a protection mechanism for
subsequent POP3 interactions. The security mechanisms used by POP3
AUTH are those used by IMAP4.
$ port scan
(I) An attack that sends client requests to a range of server port
addresses on a host, with the goal of finding an active port and
exploiting a known vulnerability of that service. (Compare: ping
sweep.)
$ positive authorization
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(I) The principle that a security architecture should be designed
so that access to system resources is granted only in a positive
way; i.e., in the absence of an explicit authorization that grants
access, the default action shall be to refuse access.
$ POSIX
(N) Portable Operating System Interface for Computer Environments,
a standard [FP151, IS9945-1] (originally IEEE Standard P1003.1)
that defines an operating system interface and environment to
support application portability at the source code level. It is
intended to be used by both application developers and system
implementers.
Tutorial: P1003.1 supports security functionality like that on
most UNIX systems, including discretionary access control and
privileges. IEEE Draft Standard P1003.6 specifies additional
functionality not provided in the base standard, including (a)
discretionary access control, (b) audit trail mechanisms, (c)
privilege mechanisms, (d) mandatory access control, and (e)
information label mechanisms.
$ Post Office Protocol, version 3 (POP3)
(I) An Internet Standard protocol (RFC 1939) by which a client
workstation can dynamically access a mailbox on a server host to
retrieve mail messages that the server has received and is holding
for the client. (See: IMAP4.)
Tutorial: POP3 has mechanisms for optionally authenticating a
client to a server and providing other security services. (See:
POP3 APOP, POP3 AUTH.)
$ PPP
(I) See: Point-to-Point Protocol.
$ PPTP
(I) See: Point-to-Point Tunneling Protocol.
$ preauthorization
(I) A CAW capability that enables certification requests to be
automatically validated against data provided in advance to the CA
by an authorizing entity.
$ precedence
(N) A designation assigned to a communication (i.e., packet,
message, data stream, connection, etc.) by the originator to state
the importance or urgency of that communication versus other
communications, and thus indicate to the transmission system the
relative order of handling, and indicate to the receiver the order
in which the communication is to be noted. [F1037] (See:
availability, critical, preemption.)
Example: The "Precedence" subfield of the "Type of Service" field
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of the IPv4 header supports the following designations (in
descending order of importance): 111 Network Control, 110
Internetwork Control, 101 CRITIC/ECP (Critical Intelligence
Communication/Emergency Command Precedence), 100 Flash Override,
011 Flash, 010 Immediate, 001 Priority, and 000 Routine. These
designations were adopted from U.S. DoD systems that existed
before ARPANET.
$ preemption
(N) The seizure, usually automatic, of system resources that are
being used to serve a lower precedence communication, in order to
serve immediately a higher precedence communication. [F1037]
$ Pretty Good Privacy(trademark) (PGP(trademark))
(O) Trademarks of Network Associates, Inc., referring to a
computer program (and related protocols) that uses cryptography to
provide data security for electronic mail and other applications
on the Internet. (Compare: MOSS, MSP, PEM, S/MIME.)
Tutorial: PGP encrypts messages with IDEA in CFB mode, distributes
the IDEA keys by encrypting them with RSA, and creates digital
signatures on messages with MD5 and RSA. To establish ownership of
public keys, PGP depends on the web of trust.
$ primary account number (PAN)
(O) /SET/ "The assigned number that identifies the card issuer and
cardholder. This account number is composed of an issuer
identification number, an individual account number
identification, and an accompanying check digit as defined by ISO
7812-1985." [SET2, IS7812] (See: bank identification number.)
Tutorial: The PAN is embossed, encoded, or both on a magnetic-
strip-based credit card. The PAN identifies the issuer to which a
transaction is to be routed and the account to which it is to be
applied unless specific instructions indicate otherwise. The
authority that assigns the BIN part of the PAN is the American
Bankers Association.
$ principal
(I) A specific identity claimed by a user when accessing a system.
Usage: Usually understood to be an identity that is registered in
and authenticated by the system; equivalent to the notion of login
account identifier. Each principal is normally assigned to a
single user, but a single user may be assigned (or attempt to use)
more than one principal. Each principal can spawn one or more
subjects, but each subject is associated with only one principal.
(Compare: role, subject, user.)
(N) /Kerberos/ A uniquely named client or server instance that
participates in a network communication.
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$ privacy
1. (I) The right of an entity (normally a person), acting in its
own behalf, to determine the degree to which it will interact with
its environment, including the degree to which the entity is
willing to share information about itself with others. (See:
HIPAA, Privacy Act of 1974. Compare: anonymity, data
confidentiality.)
2. (O) "The right of individuals to control or influence what
information related to them may be collected and stored and by
whom and to whom that information may be disclosed." [I7498 Part
2]
3. (D) Synonym for "data confidentiality".
Deprecated Definition: ISDs SHOULD NOT use this term as a synonym
for "data confidentiality" or "data confidentiality service",
which are different concepts. Privacy is a reason for security
rather than a kind of security. For example, a system that stores
personal data needs to protect the data to prevent harm,
embarrassment, inconvenience, or unfairness to any person about
whom data is maintained, and to protect the person's privacy. For
that reason, the system may need to provide data confidentiality
service.
$ Privacy Act of 1974
(O) A U.S. Federal law (Section 552a of Title 5, United States
Code) that seeks to balance the U.S. Government's need to maintain
data about individuals with the rights of individuals to be
protected against unwarranted invasions of their privacy stemming
from federal agencies' collection, maintenance, use, and
disclosure of personal data. (See: privacy.)
Tutorial: In 1974, the U.S. Congress was concerned with the
potential for abuses that could arise from the Government's
increasing use of computers to store and retrieve personal data.
Therefore, the Act has four basic policy objectives:
- To restrict disclosure of personally identifiable records
maintained by Federal agencies.
- To grant individuals increased rights of access to Federal
agency records maintained on themselves.
- To grant individuals the right to seek amendment of agency
records maintained on themselves upon a showing that the
records are not accurate, relevant, timely, or complete.
- To establish a code of "fair information practices" that
requires agencies to comply with statutory norms for
collection, maintenance, and dissemination of records.
$ Privacy Enhanced Mail (PEM)
(I) An Internet protocol to provide data confidentiality, data
integrity, and data origin authentication for electronic mail.
[R1421, R1422]. (Compare: MOSS, MSP, PGP, S/MIME.)
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Tutorial: PEM encrypts messages with DES in CBC mode, provides key
distribution of DES keys by encrypting them with RSA, and signs
messages with RSA over either MD2 or MD5. To establish ownership
of public keys, PEM uses a certification hierarchy, with X.509
public-key certificates and X.509 CRLs that are signed with RSA
and MD2.
PEM is designed to be compatible with a wide range of key
management methods, but is limited to specifying security services
only for text messages and, like MOSS, has not been widely
implemented in the Internet.
$ private component
(I) Synonym for "private key".
Deprecated Usage: In most cases, ISDs SHOULD NOT use this term;
instead, to avoid confusing readers, use "private key". However,
the term MAY be used when discussing a key pair; e.g., "A key pair
has a public component and a private component."
$ private extension
(I) See: (secondary definition under) extension.
$ private key
1. (I) The secret component of a pair of cryptographic keys used
for asymmetric cryptography. (See: key pair, public key.)
2. (O) In a public key cryptosystem, "that key of a user's key
pair which is known only by that user." [X509]
$ Private Line Interface (PLI)
(I) The first end-to-end packet encryption system for a computer
network, developed by BBN starting in 1975 for the U.S. DoD,
incorporating Government-furnished, military-grade COMSEC
equipment (TSEC/KG-34). [B1822] (Compare: IPLI.)
$ privilege
1a. (I) A synonym for "authorization". (Compare: permission.)
1b. (I) An authorization or set of authorizations to perform
security-relevant functions in the context of computer operating
systems.
Tutorial: A privilege can be modeled as (a) an action acting upon
(b) an object that contains (c) attributes that can be constrained
by (d) domains.
$ privilege management infrastructure
(O) "The infrastructure able to support the management of
privileges in support of a comprehensive authorization service and
in relationship with a" PKI; i.e., processes concerned with
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attribute certificates. [X509]
Deprecated Usage: ISDs SHOULD NOT use this term; this definition
is vague and there is no consensus on a more specific definition.
$ privileged process
(I) An computer process that is authorized (and, therefore,
trusted) to perform some security-relevant functions that ordinary
processes are not. (See: privilege, trusted process.)
$ probe
(I) /verb/ To access an information system in an attempt to gather
information about the system for the purpose of circumventing the
system's security measures.
$ procedural security
(I) Synonym for "administrative security".
Deprecated Definition: ISDs SHOULD NOT use this term as a synonym
for "administrative security". Any type of security may involve
procedures; therefore, the term may be misleading. Instead, use
"administrative security", "communication security", "computer
security", "emanations security", "personnel security", "physical
security", or whatever specific type is meant. (See: security
architecture.)
$ profile
See: certificate profile, protection profile.
$ proof-of-possession protocol
(I) A protocol whereby a system entity proves to another that it
possesses and controls a cryptographic key or other secret
information. (See: zero-knowledge proof.)
$ proprietary
(I) Refers to information (or other property) that is owned by an
individual or organization and for which the use is restricted by
that entity.
$ protected checksum
(I) A checksum that is computed for a data object by means that
protect against active attacks that would attempt to change the
checksum to make it match changes made to the data object. (See:
digital signature, keyed hash, (discussion under) checksum.
$ protective packaging
(N) Packaging techniques for COMSEC material that discourage
penetration, reveal a penetration has occurred or was attempted,
or inhibit viewing or copying of keying material prior to the time
it is exposed for use. [C4008] (Compare: QUADRANT. See: tamper
evident, tamper resistant.)
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$ protection authority
(I) See: (secondary definition under) Internet Protocol Security
Option.
$ protection profile
(N) /Common Criteria/ An implementation-independent set of
security requirements for a category of targets of evaluation that
meet specific consumer needs. [CCIB] Example: [IDSAN].
Tutorial: A protection profile (PP) is intended to be a reusable
statement of product security needs, which are known to be useful
and effective, for a set of information technology security
products that could be built. A PP contains a set of security
requirements, preferably taken from the catalogs in Parts 2 and 3
of the Common Criteria, and should include an EAL. A PP could be
developed by user communities, product developers, or any other
parties interested in defining a common set of requirements.
$ protection ring
(I) One of a hierarchy of privileged operation modes of a system
that gives certain access rights to processes authorized to
operate in that mode. (See: Multics.)
$ protective distribution system (PDS)
(N) A wireline or fiber-optic communication system used to
transmit cleartext classified information through an area of
lesser classification or control. [N7003]
$ protocol
1a. (I) A set of rules (i.e., formats and procedures) to implement
and control some type of association (e.g., communication) between
systems. Example: Internet Protocol.
1b. (I) A series of ordered computing and communication steps that
are performed by two or more system entities to achieve a joint
objective. [A9042]
$ protocol suite
(I) A complementary collection of communication protocols used in
a computer network. (See: Internet, OSI.)
$ proxy
1. (I) A computer process that acts on behalf of a user or client.
2. (I) A computer process -- often used as, or as part of, a
firewall -- that relays a protocol between client and server
computer systems, by appearing to the client to be the server and
appearing to the server to be the client. (See: SOCKS.)
Tutorial: In a firewall, a proxy server usually runs on a bastion
host, which may support proxies for several protocols (e.g., FTP,
HTTP, and TELNET). Instead of a client in the protected enclave
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connecting directly to an external server, the internal client
connects to the proxy server which in turn connects to the
external server. The proxy server waits for a request from inside
the firewall, forwards the request to the server outside the
firewall, gets the response, then sends the response back to the
client. The proxy may be transparent to the clients, or they may
need to connect first to the proxy server, and then use that
association to also initiate a connection to the real server.
Proxies are generally preferred over SOCKS for their ability to
perform caching, high-level logging, and access control. A proxy
can provide security service beyond that which is normally part of
the relayed protocol, such as access control based on peer entity
authentication of clients, or peer entity authentication of
servers when clients do not have that capability. A proxy at OSIRM
layer 7 can also provide finer-grained security service than can a
filtering router at layer 3. For example, an FTP proxy could
permit transfers out of, but not into, a protected network.
$ proxy certificate
(I) An X.509 public-key certificate derived from a end-entity
certificate, or from another proxy certificate, for the purpose of
establishing proxies and delegating authorizations in the context
of a PKI-based authentication system. [R3280]
Tutorial: A proxy certificate has the following properties:
- It contains an critical extension that (a) identifies it as a
proxy certificate and (b) may contain a certification path
length constraint and policy constraints.
- It contains the public component of a key pair that is distinct
from that associated with any other certificate.
- It is signed by the private component of a key pair that is
associated with an end-entity certificate or another proxy
certificate.
- Its associated private key can be used to sign only other proxy
certificates (not end-entity certificates).
- Its "subject" DN is derived from its "issuer" DN and is unique.
- Its "issuer" DN is the "subject" DN of an end-entity
certificate or another proxy certificate.
$ pseudorandom
(I) A sequence of values that appears to be random (i.e.,
unpredictable) but is actually generated by a deterministic
algorithm. (See: compression, random, random number generator.)
$ pseudorandom number generator
See: random number generator.
$ public component
(I) Synonym for "public key".
Deprecated Usage: In most cases, ISDs SHOULD NOT use this term; to
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avoid confusing readers, use "private key" instead. However, the
term MAY be used when discussing a key pair; e.g., "A key pair has
a public component and a private component."
$ public key
1. (I) The publicly-disclosable component of a pair of
cryptographic keys used for asymmetric cryptography. (See: key
pair, private key.)
2. (O) In a public key cryptosystem, "that key of a user's key
pair which is publicly known." [X509]
$ public-key certificate
1. (I) A digital certificate that binds a system entity's identity
to a public key value, and possibly to additional, secondary data
items; i.e., a digitally-signed data structure that attests to the
ownership of a public key. (See: X.509 public-key certificate.)
2. (O) "The public key of a user, together with some other
information, rendered unforgeable by encipherment with the private
key of the certification authority which issued it." [X509]
Tutorial: The digital signature on a public-key certificate is
unforgeable. Thus, the certificate can be published, such as by
posting it in a directory, without the directory having to protect
the certificate's data integrity.
$ public-key cryptography
(I) The popular synonym for "asymmetric cryptography".
$ Public-Key Cryptography Standards (PKCS)
(N) A series of specifications published by RSA Laboratories for
data structures and algorithm used in basic applications of
asymmetric cryptography. (See: PKCS #5 through PKCS #11.)
Tutorial: The PKCS were begun in 1991 in cooperation with industry
and academia, originally including Apple, Digital, Lotus,
Microsoft, Northern Telecom, Sun, and MIT. Today, the
specifications are widely used, but they are not sanctioned by an
official standards organization, such as ANSI, ITU-T, or IETF. RSA
Laboratories retains sole decision-making authority over the PKCS.
$ public-key forward secrecy (PFS)
(I) For a key agreement protocol based on asymmetric cryptography,
the property that ensures that a session key derived from a set of
long-term public and private keys will not be compromised if one
of the private keys is compromised in the future.
Usage: Some existing RFCs use the term "perfect forward secrecy"
but either do not define it or do not define it precisely. While
preparing this Glossary, we tried to find a good definition for
that term, but found this to be a muddled area. Experts did not
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agree. For all practical purposes, the literature defines "perfect
forward secrecy" by stating the Diffie-Hellman algorithm. The term
"public-key forward secrecy" (suggested by Hilarie Orman) and the
"I" definition stated for it here were crafted to be compatible
with current Internet documents, yet be narrow and leave room for
improved terminology.
Challenge to the Internet security community: We need a taxonomy
-- a family of mutually exclusive and collectively exhaustive
terms and definitions to cover the basic properties discussed here
-- for the full range of cryptographic algorithms and protocols
used in Internet Standards:
Involvement of session keys vs. long-term keys: Experts disagree
about the basic ideas involved:
- One concept of "forward secrecy" is that, given observations of
the operation of a key establishment protocol up to time t, and
given some of the session keys derived from those protocol
runs, you cannot derive unknown past session keys or future
session keys.
- A related property is that, given observations of the protocol
and knowledge of the derived session keys, you cannot derive
one or more of the long-term private keys.
- The "I" definition presented above involves a third concept of
"forward secrecy" that refers to the effect of the compromise
of long-term keys.
- All three concepts involve the idea that a compromise of "this"
encryption key is not supposed to compromise the "next" one.
There also is the idea that compromise of a single key will
compromise only the data protected by the single key. In
Internet literature, the focus has been on protection against
decryption of back traffic in the event of a compromise of
secret key material held by one or both parties to a
communication.
Forward vs. backward: Experts are unhappy with the word "forward",
because compromise of "this" encryption key also is not supposed
to compromise the "previous" one, which is "backward" rather than
forward. In S/KEY, if the key used at time t is compromised, then
all keys used prior to that are compromised. If the "long-term"
key (i.e., the base of the hashing scheme) is compromised, then
all keys past and future are compromised; thus, you could say that
S/KEY has neither forward nor backward secrecy.
Asymmetric cryptography vs. symmetric: Experts disagree about
forward secrecy in the context of symmetric cryptographic systems.
In the absence of asymmetric cryptography, compromise of any long-
term key seems to compromise any session key derived from the
long-term key. For example, Kerberos isn't forward secret, because
compromising a client's password (thus compromising the key shared
by the client and the authentication server) compromises future
session keys shared by the client and the ticket-granting server.
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Ordinary forward secrecy vs. "perfect" forward secret: Experts
disagree about the difference between these two. Some say there is
no difference, and some say that the initial naming was
unfortunate and suggest dropping the word "perfect". Some suggest
using "forward secrecy" for the case where one long-term private
key is compromised, and adding "perfect" for when both private
keys (or, when the protocol is multi-party, all private keys) are
compromised.
Acknowledgements: Bill Burr, Burt Kaliski, Steve Kent, Paul Van
Oorschot, Michael Wiener, and, especially, Hilarie Orman
contributed ideas to this discussion.
$ public-key infrastructure (PKI)
1. (I) A system of CAs (and, optionally, RAs and other supporting
servers and agents) that perform some set of certificate
management, archive management, key management, and token
management functions for a community of users in an application of
asymmetric cryptography. (See: hierarchical PKI, mesh PKI,
security management infrastructure, trust-file PKI.)
2. (I) /PKIX/ The set of hardware, software, people, policies, and
procedures needed to create, manage, store, distribute, and revoke
digital certificates based on asymmetric cryptography.
Tutorial: The core PKI functions are (a) to register users and
issue their public-key certificates, (b) to revoke certificates
when required, and (c) to archive data needed to validate
certificates at a much later time. Key pairs for data
confidentiality may be generated (and perhaps escrowed) by CAs or
RAs, but requiring a PKI client to generate its own digital
signature key pair helps maintain system integrity of the
cryptographic system, because then only the client ever possesses
the private key it uses. Also, an authority may be established to
approve or coordinate CPSs, which are security policies under
which components of a PKI operate.
A number of other servers and agents may support the core PKI, and
PKI clients may obtain services from them. The full range of such
services is not yet fully understood and is evolving, but
supporting roles may include archive agent, certified delivery
agent, confirmation agent, digital notary, directory, key escrow
agent, key generation agent, naming agent who ensures that issuers
and subjects have unique identifiers within the PKI, repository,
ticket-granting agent, and time stamp agent.
$ purge
(I) Use degaussing or other means to render (magnetically) stored
data unusable and unrecoverable by any means, including laboratory
methods. [C4009] (See: zeroize. Compare: erase, sanitize.)
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$ QUADRANT
(O) /U.S. Government/ Short name for technology and methods that
protect cryptographic equipment by making the equipment tamper-
resistant. [C4009] (Compare: protective packaging, TEMPEST.)
Tutorial: Equipment cannot be made completely tamper-proof, but it
can be made tamper-resistant or tamper-evident.
$ qualified certificate
(I) A public-key certificate that has the primary purpose of
identifying a person with a high level of assurance, where the
certificate meets some qualification requirements defined by an
applicable legal framework, such as the European Directive on
Electronic Signature [EU-ESDIR]. [R3739].
$ RA
(I) See: registration authority.
$ RA domains
(I) A capability of a CAW that allows a CA to divide the
responsibility for certificate requests among multiple RAs.
Tutorial: This capability might be used to restrict access to
private authorization data that is provided with a certificate
request, and to distribute the responsibility to review and
approve certificate requests in high volume environments. RA
domains might segregate certificate requests according to an
attribute of the certificate subject, such as an organizational
unit.
$ RADIUS
(I) See: Remote Authentication Dial-In User Service.
$ Rainbow Series
(O) A set of more than 30 technical and policy documents with
colored covers, issued by the NCSC, that discuss in detail the
TCSEC and provide guidance for meeting and applying the criteria.
(See: Green Book, Orange Book, Red Book, Yellow Book.)
$ random
(I) In essence, "random" means "unpredictable". [SP22, Knut,
R1750] (See: cryptographic key, pseudorandom.)
- "Random sequence": A sequence in which each successive value is
obtained merely by chance and does not depend on the preceding
values of the sequence. In a random sequence of bits, each bit
is unpredictable; i.e., (a) the probability of each bit being a
"0" or "1" is 1/2, and (b) the value of each bit is independent
of any other bit in the sequence.
- "Random value": A individual value that is unpredictable; i.e.,
each value in the total population of possibilities has equal
probability of being selected.
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$ random number generator
(I) A process that is invoked to generate a random sequence of
values (usually a sequence of bits) or an individual random value.
Tutorial: There are two basic types of generators. [SP22]
- (True) random number generator: Uses one or more non-
deterministic bit sources (usually physical phenomena; e.g.,
electrical circuit noise, timing of user processes such as key
strokes or mouse movements, semiconductor quantum effects) and
some processing function that formats the bits; and outputs an
sequence of values that is unpredictable and uniformly
distributed.
- Pseudorandom number generator: Uses a deterministic
computational process (usually implemented by software) that
has one or more inputs called "seeds"; and outputs a sequence
of values that appears to be random according to specified
statistical tests.
$ RBAC
(N) See: role-based access control, rule-based access control.
Deprecated Usage: This abbreviation is ambiguous; therefore, ISDs
that use it SHOULD state a definition for it.
$ RC2, RC4, RC6
(N) See: Rivest Cipher #2, #4, #6.
$ read
(I) A fundamental operation in an information system that results
only in the flow of information from an object to a subject. (See:
access mode.)
$ realm
(O) /Kerberos/ The domain of authority of a Kerberos server
(consisting of an authentication server and a ticket-granting
server), including the Kerberized clients and the Kerberized
application servers
$ recovery
1. (I) /cryptography/ The process of learning or obtaining
cryptographic data or plain text through cryptanalysis. (See: key
recovery, data recovery.)
2a. (I) /system integrity/ The process of restoring a secure state
in a system after there has been an accidental failure or a
successful attack. (See: system integrity.)
2b. (I) /system integrity/ The process of restoring an information
system's assets and operation following damage or destruction.
(See: contingency plan.)
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$ RED
1. (I) Designation for data that consists only of clear text, and
for information system equipment items and facilities that handle
only clear text. Example: "RED key". (Compare: BLACK. See: color
change, RED/BLACK separation.)
Derivation: From the practice of marking equipment with colors to
prevent operational errors.
2. (O) /U.S. Government/ Designation applied to information
systems, and to associated areas, circuits, components, and
equipment, "in which unencrypted national security information is
being processed." [C4009]
$ RED/BLACK separation
(I) An architectural concept for cryptographic systems that
strictly separates the parts of a system that handle plain text
(i.e., RED information) from the parts that handle cipher text
(i.e., BLACK information). (See: BLACK, RED.)
$ Red Book
(D) Synonym for "Trusted Network Interpretation of the Trusted
Computer System Evaluation Criteria" [NCS05].
Deprecated Term: ISDs SHOULD NOT use this term as a synonym for
"Trusted Network Interpretation of the Trusted Computer System
Evaluation Criteria". Instead, use the full proper name of the
document or, in subsequent references, a more conventional
abbreviation. (See: TCSEC, Rainbow Series, (Deprecated Usage
under) Green Book.)
$ RED key
(I) A key that is usable in its present form without any
additional decryption. (Compare: BLACK key. See: RED.)
$ reference monitor
(I) "An access control concept that refers to an abstract machine
that mediates all accesses to objects by subjects." [NCS04] (See:
security kernel.)
Tutorial: This concept was described in the Anderson report. A
reference monitor should be (a) complete (i.e., it mediates every
access), (b) isolated (i.e., it cannot be modified by other system
entities), and (c) verifiable (i.e., small enough to be subjected
to analysis and tests to ensure that it is correct).
$ reflection attack
(I) An attack in which a valid data transmission is maliciously or
fraudulently retransmitted, either by an adversary who intercepts
the data or by its originator. (Compare: replay attack.)
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$ registration
1. (I) A system process that (a) initializes an identity in the
system, (b) establishes an identifier for that identity, (c) may
associate authentication information with that identifier, and (d)
may issue an identifier credential (depending on the type of
authentication mechanism being used). (See: authentication
information, credential, identifier, identity.)
2. (I) /PKI/ An administrative act or process whereby an entity's
name and other attributes are established for the first time at a
CA, prior to the CA issuing a digital certificate that has the
entity's name as the subject. (See: registration authority.)
Tutorial: Registration may be accomplished either directly, by the
CA, or indirectly, by a separate RA. An entity is presented to the
CA or RA, and the authority either records the name(s) claimed for
the entity or assigns the entity's name(s). The authority also
determines and records other attributes of the entity that are to
be bound in a certificate (such as a public key or authorizations)
or maintained in the authority's database (such as street address
and telephone number). The authority is responsible, possibly
assisted by an RA, for verifying the entity's identity and vetting
the other attributes, in accordance with the CA's CPS.
Among the registration issues that a CPS may address are the
following [R2527]:
- How a claimed identity and other attributes are verified.
- How organization affiliation or representation is verified.
- What forms of names are permitted, such as X.500 DN, domain
name, or IP address.
- Whether names are required to be meaningful or unique, and
within what domain.
- How naming disputes are resolved, including the role of
trademarks.
- Whether certificates are issued to entities that are not
persons.
- Whether a person is required to appear before the CA or RA, or
can instead be represented by an agent.
- Whether and how an entity proves possession of the private key
matching a public key.
$ registration authority (RA)
1. (I) An optional PKI entity (separate from the CAs) that does
not sign either digital certificates or CRLs but has
responsibility for recording or verifying some or all of the
information (particularly the identities of subjects) needed by a
CA to issue certificates and CRLs and to perform other certificate
management functions. (See: ORA, registration.)
2. (I) /PKIX/ An optional PKI component, separate from the CA(s).
The functions that the RA performs will vary from case to case but
may include identity authentication and name assignment, key
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generation and archiving of key pairs, token distribution, and
revocation reporting. [R2510]
Tutorial: Sometimes, a CA may perform all certificate management
functions for all end users for which the CA signs certificates.
Other times, such as in a large or geographically dispersed
community, it may be necessary or desirable to offload secondary
CA functions and delegate them to an assistant, while the CA
retains the primary functions (signing certificates and CRLs). The
tasks that are delegated to an RA by a CA may include personal
authentication, name assignment, token distribution, revocation
reporting, key generation, and archiving. An RA is an optional PKI
component, separate from the CA, that is assigned secondary
functions. The duties assigned to RAs vary from case to case but
may include the following:
- Verifying a subject's identity, i.e., performing personal
authentication functions.
- Assigning a name to a subject. (See: distinguished name.)
- Verifying that a subject is entitled to have the attributes
requested for a certificate.
- Verifying that a subject possesses the private key that matches
the public key requested for a certificate.
- Performing functions beyond mere registration, such as
generating key pairs, distributing tokens, and handling
revocation reports. (Such functions may be assigned to a PKI
component that is separate from both the CA and the RA.)
3. (O) /SET/ "An independent third-party organization that
processes payment card applications for multiple payment card
brands and forwards applications to the appropriate financial
institutions." [SET2]
$ regrade
(I) Deliberately change the classification level of information in
an authorized manner. (See: downgrade, upgrade.)
$ rekey
(I) Change the value of a cryptographic key that is being used in
an application of a cryptographic system. (See: certificate
rekey.)
Tutorial: Rekey is required at the end of a cryptoperiod or key
lifetime.
$ reliability
(I) The ability of a system to perform a required function under
stated conditions for a specified period of time. (Compare:
availability, survivability.)
$ reliable human review
(I) Any manual, automated, or hybrid process or procedure for
opening and reviewing a digital object, such as text or an image,
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to determine whether the object may be permitted, according to
some security policy, to be transferred across a controlled
interface. (See: guard.)
$ relying party
(I) Synonym for "certificate user".
Usage: Used in a legal context to mean a recipient of a
certificate who acts in reliance on that certificate. (See: ABA
Guidelines.)
$ remanence
(I) Residual information that can be recovered from a storage
medium after clearing. (See: clear, magnetic remanence, purge.)
$ Remote Authentication Dial-In User Service (RADIUS)
(I) An Internet protocol [R2138] for carrying dial-in users'
authentication information and configuration information between a
shared, centralized authentication server (the RADIUS server) and
a network access server (the RADIUS client) that needs to
authenticate the users of its network access ports. (See: TACACS.)
Tutorial: A user of the RADIUS client presents authentication
information to the client, and the client passes that information
to the RADIUS server. The server authenticates the client using a
shared secret value, then checks the user's authentication
information, and finally returns to the client all authorization
and configuration information needed by the client to deliver
service to the user.
$ renew
See: certificate renewal.
$ replay attack
(I) An attack in which a valid data transmission is maliciously or
fraudulently repeated, either by the originator or by an adversary
who intercepts the data and retransmits it, possibly as part of a
masquerade attack. (See: active wiretapping. Compare: reflection
attack.)
$ repository
1. (I) A system for storing and distributing digital certificates
and related information (including CRLs, CPSs, and certificate
policies) to certificate users. (See: archive, directory.)
2. (O) "A trustworthy system for storing and retrieving
certificates or other information relevant to certificates." [ABA]
Tutorial: A certificate is published to those who might need it by
putting it in a repository. The repository usually is a publicly
accessible, on-line server. In the Federal Public-key
Infrastructure, for example, the expected repository is a
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directory that uses LDAP, but also may be the X.500 Directory that
uses DAP, or an HTTP server, or an FTP server that permits
anonymous login.
$ repudiation
1. (I) Denial by a system entity that was involved in an
association (especially an association that transfers information)
of having participated in the relationship. (See: accountability,
non-repudiation service.)
2. (I) A type of threat action whereby an entity deceives another
by falsely denying responsibility for an act. (See: deception.)
Usage: This type of threat action includes the following subtypes:
- False denial of origin: Action whereby an originator denies
responsibility for sending data.
- False denial of receipt: Action whereby a recipient denies
receiving and possessing data.
3. (O) /OSIRM/ "Denial by one of the entities involved in a
communication of having participated in all or part of the
communication." [I7498 Part 2]
$ Request for Comment (RFC)
(I) One of the documents in the archival series that is the
official channel for ISDs and other publications of the Internet
Engineering Steering Group, the Internet Architecture Board, and
the Internet community in general. [R2026, R2223] (See: Internet
Standard.)
Deprecated Usage: This term is NOT a synonym for "Internet
Standard".
$ residual risk
(I) The portion of an original risk or set of risks that remains
after countermeasures have been applied. (Compare: acceptable
risk, risk analysis.)
$ restore
See: card restore.
$ revocation
See: certificate revocation.
$ revocation date
(N) /X.509/ In a CRL entry, a date-time field that states when the
certificate revocation occurred, i.e., when the CA declared the
digital certificate to be invalid. (See: invalidity date.)
Tutorial: The revocation date may not resolve some disputes
because, in the worst case, all signatures made during the
validity period of the certificate may have to be considered
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invalid. However, it may be desirable to treat a digital signature
as valid even though the private key used to sign was compromised
after the signing. If more is known about when the compromise
actually occurred, a second date-time, an "invalidity date", can
be included in an extension of the CRL entry.
$ revocation list
See: certificate revocation list.
$ revoke
(I) See: certificate revocation.
$ RFC
(I) See: Request for Comment.
$ Rijndael
(I) A block cipher, designed by Joan Daemen and Vincent Rijmen as
a candidate algorithm for the AES. [Daem]
$ risk
1. (I) An expectation of loss expressed as the probability that a
particular threat will exploit a particular vulnerability with a
particular harmful result.
2. (O) /SET/ "The possibility of loss because of one or more
threats to information (not to be confused with financial or
business risk)." [SET2]
$ risk analysis
(I) An assessment process that systematically (a) identifies
valuable system resources and threats to those resources, (b)
quantifies loss exposures (i.e., loss potential) based on
estimated frequencies and costs of occurrence, and (c)
(optionally) recommends how to allocate resources to
countermeasures so as to minimize total exposure. (See: risk
management.)
Tutorial: There are four basic options for dealing with a risk
[SP30]:
- Risk avoidance: Eliminate the risk either by countering the
threat or removing the vulnerability.
- Risk transference: Shift the risk to another system or system
entity, such as by buying insurance to compensate for loss.
- Risk limitation: Limit the risk by implementing controls that
minimize the resulting loss.
- Risk assumption: Accept the potential for loss and continue
operating the system.
Usually, it is financially and technically infeasible to avoid or
transfer all risks (see: (first corollary of second law under)
Courtney's laws), and so some residual risk will remain, even
after all available countermeasures have been deployed (see:
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(second corollary of second law under) Courtney's laws). Thus, a
risk analysis typically lists risks in order of cost and
criticality, thereby determining where countermeasures should be
applied first. [FP031, R2196]
In some contexts, it is infeasible to do a risk analysis because
needed data and resources are not available, or it is inadvisable.
Instead, answers to questions about threats and risks may be
already built into basic institutional security policies. For
example, U.S. DoD policies for data confidentiality "do not
explicitly itemize the range of expected threats" but instead
"reflect an operational approach ... by stating the particular
management controls that must be used to achieve [confidentiality]
severe risk in itself, and avoid the risk of poor security design
implicit in taking a fresh approach to each new problem". [NRC91]
$ risk management
1. (I) The process of identifying, measuring, and controlling
(i.e., mitigating) risks in information systems so as to reduce
the risks to a level commensurate with the value of the assets
protected. (See: risk analysis.)
2. (I) The process of controlling uncertain events that may affect
information system resources.
3. (O) "The total process of identifying, controlling, and
mitigating information system-Drelated risks. It includes risk
assessment; cost-benefit analysis; and the selection,
implementation, test, and security evaluation of safeguards. This
overall system security review considers both effectiveness and
efficiency, including impact on the mission and constraints due to
policy, regulations, and laws." [SP30]
$ Rivest Cipher #2 (RC2)
(N) A proprietary, variable-key-length block cipher invented by
Ron Rivest for RSA Data Security, Inc.
$ Rivest Cipher #4 (RC4)
(N) A proprietary, variable-key-length stream cipher invented by
Ron Rivest for RSA Data Security, Inc.
$ Rivest Cipher #6 (RC6)
(N) A block cipher with 128-bit or higher key size; invented by
Ron Rivest for RSA Data Security, Inc. A finalist in the
competition for AES.
$ Rivest-Shamir-Adleman (RSA)
(N) An algorithm for asymmetric cryptography, invented in 1977 by
Ron Rivest, Adi Shamir, and Leonard Adleman [RSA78].
Tutorial: RSA uses exponentiation modulo the product of two large
prime numbers. The difficulty of breaking RSA is believed to be
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equivalent to the difficulty of factoring integers that are the
product of two large prime numbers of approximately equal size.
To create an RSA key pair, randomly choose two large prime
numbers, p and q, and compute the modulus, n = pq. Randomly choose
a number e, the public exponent, that is less than n and
relatively prime to (p-1)(q-1). Choose another number d, the
private exponent, such that ed-1 evenly divides (p-1)(q-1). The
public key is the set of numbers (n,e), and the private key is the
set (n,d).
It is assumed to be difficult to compute the private key (n,d)
from the public key (n,e). However, if n can be factored into p
and q, then the private key d can be computed easily. Thus, RSA
security depends on the assumption that it is computationally
difficult to factor a number that is the product of two large
prime numbers. (Of course, p and q are treated as part of the
private key, or else are destroyed after computing n.)
For encryption of a message, m, to be sent to Bob, Alice uses
Bob's public key (n,e) to compute m**e (mod n) = c. She sends c to
Bob. Bob computes c**d (mod n) = m. Only Bob knows d, so only Bob
can compute c**d (mod n) to recover m.
To provide data origin authentication of a message, m, to be sent
to Bob, Alice computes m**d (mod n) = s, where (d,n) is Alice's
private key. She sends m and s to Bob. To recover the message that
only Alice could have sent, Bob computes s**e (mod n) = m, where
(e,n) is Alice's public key.
To ensure data integrity in addition to data origin authentication
requires extra computation steps in which Alice and Bob use a
cryptographic hash function h (see: digital signature). Alice
computes the hash value h(m) = v, and then encrypts v with her
private key to get s. She sends m and s. Bob receives m' and s',
either of which might have been changed from the m and s that
Alice sent. To test this, he decrypts s' with Alice's public key
to get v'. He then computes h(m') = v". If v' equals v", Bob is
assured that m' is the same m that Alice sent.
$ robustness
(N) See: level of robustness.
$ role
1. (I) A job function (or a job title that implies a set of
functions) to which people or other system entities are assigned,
within an organization or other system. (Compare: duty, billet,
principal, user. See: role-based access control.)
2. (O) /Common Criteria/ A pre-defined set of rules establishing
the allowed interactions between a user and the TOE.
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$ role-based access control
(I) A form of identity-based access control wherein the system
entities that are identified and controlled are functional
positions in an organization or process. [Sand] (See:
authorization, constraint, identity, principal, role.)
Tutorial: Administrators assign permissions to roles as needed to
perform functions in the system. Administrators separately assign
user identities to roles. When a user accesses the system in an
identity (for which the user has been registered) and initiates a
session using a role (to which the user has been assigned), then
the permissions that have been assigned to the role are available
to be exercised by the user.
The following diagram shows that role-based access control
involves five types relationships. Administrators assign (a)
identities to roles, (b) permissions to roles, and (c) roles to
roles; and users select (d) identities in sessions, and (e) roles
in sessions. Security policies may define constraints on these
assignments and selections.
(c) Permission Inheritance Assignments (i.e., Role Hierarchy)
[Constraints]
+=====+
| |
(a) Identity v v (b) Permission
+----------+ Assignments +-------+ Assignments +----------+
|Identities|<=============>| Roles |<=============>|Permissions|
+----------+ [Constraints] +-------+ [Constraints] +----------+
| | ^ ^
| | +-----------+ | | +---------------------+
| | | +-------+ | | | | Legend |
| +====>|Session|=====+ | | |
| | +-------+ | | | One-to-One |
| | ... | | | =================== |
| | +-------+ | | | |
+========>|Session|=========+ | One-to-Many |
(d) Identity | +-------+ | (e) Role | ==================> |
Selections | | Selections | |
[Constraints]| Access |[Constraints] | Many-to-Many |
| Sessions | | <=================> |
+-----------+ +---------------------+
$ role certificate
(I) An organizational certificate that is issued to a system
entity that is a member of the set of users that have identities
that are assigned to a particular role. (See: role-based access
control.)
$ root
1. (I) A CA that is directly trusted by an end entity.
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2. (I) /hierarchical PKI/ The CA that is the highest level (most
trusted) CA in a certification hierarchy; i.e., the authority upon
whose public key all certificate users base their validation of
certificates, CRLs, certification paths, and other constructs.
(See: top CA.)
Tutorial: The root CA in a certification hierarchy issues public-
key certificates to one or more additional CAs that form the
second highest level. Each of these CAs may issue certificates to
more CAs at the third highest level, and so on. To initialize
operation of a hierarchical PKI, the root's initial public key is
securely distributed to all certificate users in a way that does
not depend on the PKI's certification relationships, i.e., by an
out-of-band procedure. The root's public key may be distributed
simply as a numerical value, but typically is distributed in a
self-signed certificate in which the root is the subject. The
root's certificate is signed by the root itself because there is
no higher authority in a certification hierarchy. The root's
certificate is then the first certificate in every certification
path.
3. (O) /MISSI/ A name previously used for a MISSI policy creation
authority, which is not a root as defined above for general usage,
but is a CA at the second level of the MISSI hierarchy,
immediately subordinate to a MISSI policy approving authority.
4. (O) /UNIX/ A user account (also called "superuser") that has
all privileges (including all security-related privileges) and
thus can manage the system and its other user accounts.
5. (O) /DNS/ The base of the tree structure that defines the name
space for the Internet DNS. (See: domain name.)
$ root certificate
1. (I) A certificate for which the subject is a root.
2. (I) /hierarchical PKI/ The self-signed public-key certificate
at the top of a certification hierarchy.
$ root key
(I) A public key for which the matching private key is held by a
root.
$ root registry
(O) /MISSI/ A name previously used for a MISSI PAA.
$ ROT13
(I) See: Caeser cipher.
$ router
1. (I) /IP/ A networked computer that forwards IP packets that are
not addressed to the computer itself. (Compare: host.)
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2. (I) /OSIRM/ A computer that is a gateway between two networks
at OSIRM layer 3 and that relays and directs data packets through
that internetwork. The most common form of router operates on IP
packets. (Compare: bridge, proxy.)
$ RSA
(N) See: Rivest-Shamir-Adleman.
$ rule
See: security rule.
$ rule-based security policy
(I) "A security policy based on global rules imposed for all
users. These rules usually rely on comparison of the sensitivity
of the resource being accessed and the possession of corresponding
attributes of users, a group of users, or entities acting on
behalf of users." [I7498 Part 2] (Compare: identity-based security
policy, RBAC.)
$ rules of behavior
(I) A body of security policy that has been established and
implemented concerning the responsibilities and expected behavior
of entities that have access to a system. (Compare: [R1281].)
Tutorial: For persons employed by a corporation or government, the
rules might cover such matters as working at home, remote access,
use of the Internet, use of copyrighted works, use of system
resources for unofficial purpose, assignment and limitation of
system privileges, and individual accountability.
$ S field
(D) See: Security Level field.
$ S-BGP
(I) See: Secure BGP.
$ S-HTTP
(I) See: Secure Hypertext Transfer Protocol.
$ S/Key
(I) A security mechanism that uses a cryptographic hash function
to generate a sequence of 64-bit, one-time passwords for remote
user login. [R1760]
Tutorial: The client generates a one-time password by applying the
MD4 cryptographic hash function multiple times to the user's
secret key. For each successive authentication of the user, the
number of hash applications is reduced by one. (Thus, an intruder
using wiretapping cannot compute a valid password from knowledge
of one previously used.) The server verifies a password by hashing
the currently presented password (or initialization value) one
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time and comparing the hash result with the previously presented
password.
$ S/MIME
(I) See: Secure/MIME.
$ SAD
(I) See: Security Association Database.
$ safety
(I) The property of a system being free from risk of causing harm
(especially physical harm) to its system entities. (Compare:
security.)
$ SAID
(I) See: security association identifier.
$ salt
(I) A data value used to vary the results of a computation in a
security mechanism, so that an exposed computational result from
one instance of applying the mechanism cannot be reused by an
attacker in another instance. (Compare: initialization value.)
Example: A password-based access control mechanism might protect
against capture or accidental disclosure of its password file by
applying a one-way encryption algorithm to passwords before
storing them in the file. To increase the difficulty of off-line,
dictionary attacks that match encrypted values of potential
passwords against a copy of the password file, the mechanism can
concatenate each password with its own random salt value before
applying the one-way function.
$ SAML
(N) See: Security Assertion Markup Language (SAML).
$ sandbox
(I) A restricted, controlled execution environment that prevents
potentially malicious software, such as mobile code, from
accessing any system resources except those for which the software
is authorized.
$ sanitize
(I) Delete sensitive data from a file, a device, or a system; or
modify data so as to be able to downgrade its classification
level.
$ SAP
(O) See: special access program.
$ SASL
(I) See: Simple Authentication and Security Layer.
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$ SCA
(I) See: subordinate certification authority.
$ scavenging
(I) See: (secondary definition under) threat consequence.
$ SCI
(O) See: sensitive compartmented information.
$ SCIF
(O) See: sensitive compartmented information facility.
$ SCOMP
(N) Secure COMmunications Processor; an enhanced, MLS version of
the Honeywell Level 6 minicomputer. It was the first system to be
rated in TCSEC Class A1. (See: KSOS.)
$ screen room
(I) /slang/ Synonym for "shielded enclosure".
$ screening router
(I) Synonym for "filtering router".
$ script kiddy
(D) /slang/ A cracker who is able to use existing attack
techniques (i.e., to read scripts) and execute existing attack
software, but is unable to invent new exploits or manufacture the
tools to perform them; pejoratively, an immature or novice
cracker. (See: packet monkey.)
Deprecated Term: It is likely that other cultures have different
metaphors for this concept. Therefore, to ensure international
understanding, ISDs SHOULD NOT use this term. (See: (Deprecated
Usage under) Green Book.)
$ SDE
(N) See: Secure Data Exchange.
$ SDNS
(O) See: Secure Data Network System.
$ seal
1. (I) To use asymmetric cryptography to encrypt plain text with a
public key in such a way that only the holder of the matching
private key can learn what was the plain text. [Chau]
Usage: The definition is not widely known; therefore, ISDs that
use this term SHOULD state a definition for it.
Tutorial: The definition does *not* say "only the holder of the
matching private key can decrypt the ciphertext to learn what was
the plaintext"; sealing is stronger than that. If Alice simply
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encrypts a plaintext P with a public key K to produce ciphertext C
= K(P), then if Bob guesses that P = X, Bob could verify the guess
by checking whether K(P) = K(X). To "seal" P and block Bob's
guessing attack, Alice could attach a long string R of random bits
to P before encrypting to produce C = K(P,R); if Bob guesses that
P = X, Bob can only test the guess by also guessing R.
2. (D) To use cryptography to provide data integrity service for a
data object. (See: sign.)
Deprecated Definition: ISDs SHOULD NOT use this term with this
definition. Instead, use a term that is more specific with regard
to the mechanism(s) used to provide the data integrity service;
e.g., use "sign" when the mechanism is digital signature.
$ secret
1a. (I) /adjective/ The condition of information being protected
from being known by any system entities except those that are
intended to know it.
1b. (I) /noun/ An item of information that is protected thusly.
Usage: This term applies to symmetric keys, private keys, and
passwords.
$ secret-key cryptography
(D) Synonym for "symmetric cryptography".
Deprecated Term: ISDs SHOULD NOT use this term; it could be
confused with asymmetric cryptography, in which the private key is
secret.
Derivation: Symmetric cryptography is sometimes called "secret-key
cryptography" because entities that share the key, such as the
originator and the recipient of a message, need to keep the key
secret from other entities.
$ Secure BGP (S-BGP)
(I) A project of BBN Technologies, sponsored by the U.S. DoD's
Defense Advanced Research Projects Agency, to design and
demonstrate an architecture to secure the Border Gateway Protocol
(RFC 1771) and to promote deployment of that architecture in the
Internet.
Tutorial: S-BGP incorporates three security mechanisms:
- A PKI supports authentication of ownership of IP address
blocks, autonomous system (AS) numbers, an AS's identity, and a
BGP router's identity and its authorization to represent an AS.
This PKI parallels and takes advantage of the Internet's
existing IP address and AS number assignment system.
- A new, optional, BGP transitive path attribute carries digital
signatures (in "attestations") covering the routing information
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in a BGP UPDATE. These signatures along with certificates from
the S-BGP PKI enable the receiver of a BGP routing UPDATE to
verify the address prefixes and path information that it
contains.
- IPsec provides data and partial sequence integrity, and enables
BGP routers to authenticate each other for exchanges of BGP
control traffic.
$ Secure Data Exchange (SDE)
(N) A LAN security protocol defined by the IEEE 802.10 standard.
$ Secure Data Network System (SDNS)
(O) An NSA program that developed security protocols for
electronic mail (see: MSP), OSIRM layer 3 (see: SP3), OSIRM layer
4 (see: SP4), and key management (see: KMP).
$ Secure Hash Algorithm (SHA)
(N) A cryptographic hash function (specified in SHS) that produces
a 160-bit output (hash result) for input data of any length <
2**64 bits.
$ Secure Hash Standard (SHS)
(N) The U.S. Government standard [FP180] that specifies SHA.
$ Secure Hypertext Transfer Protocol (S-HTTP)
(I) A Internet protocol (RFC 2660) for providing client-server
security services for HTTP communications. (Compare: https.)
Tutorial: S-HTTP was originally specified by CommerceNet, a
coalition of businesses interested in developing the Internet for
commercial uses. Several message formats may be incorporated into
S-HTTP clients and servers, particularly CMS and MOSS. S-HTTP
supports choice of security policies, key management mechanisms,
and cryptographic algorithms through option negotiation between
parties for each transaction. S-HTTP supports modes of operation
for both asymmetric and symmetric cryptography. S-HTTP attempts to
avoid presuming a particular trust model, but it attempts to
facilitate multiply-rooted hierarchical trust and anticipates that
principals may have many public-key certificates.
$ Secure/MIME (S/MIME)
(I) Secure/Multipurpose Internet Mail Extensions, an Internet
protocol (RFC 3851) to provide encryption and digital signatures
for Internet mail messages.
$ secure multicast
(I) Refers generally to providing security services for multicast
groups of various types (e.g., 1-to-N and M-to-N) and to classes
of protocols used to protect multicast packets.
Tutorial: Multicast applications include video broadcast and
multicast file transfer, and many of these applications require
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network security services. The Multicast Security Reference
Framework [R3740] covers three functional areas:
- Multicast data handling: Security-related treatment of
multicast data by the sender and the receiver.
- Group key management: Secure distribution and refreshment of
keying material. (See: Group Domain of Interpretation.)
- Multicast security policy: Policy translation and
interpretation across the multiple administrative domains that
typically are spanned by a multicast application.
$ Secure Shell(trademark) (SSH(trademark))
(N) Trademarks of SSH Communications Security Corp. that refer to
a protocol for secure remote login and other secure network
services.
Tutorial: SSH has three main parts:
- Transport layer protocol: Provides server authentication,
confidentiality, and integrity; and can optionally provide
compression. This layer typically runs over a TCP/IP
connection, but might also run on top of any other reliable
data stream.
- User authentication protocol: Authenticates the client-side
user to the server. It runs over the transport layer protocol.
- Connection protocol: Multiplexes the encrypted tunnel into
several logical channels. It runs over the user authentication
protocol.
$ Secure Sockets Layer (SSL)
(N) An Internet protocol (originally developed by Netscape
Communications, Inc.) that uses connection-oriented end-to-end
encryption to provide data confidentiality service and data
integrity service for traffic between a client (often a web
browser) and a server, and that can optionally provide peer entity
authentication between the client and the server. (See: Transport
Layer Security.)
Tutorial: The name misleadingly suggests that SSL is situated in
the IPS transport layer, but SSL is layered above a reliable
transport protocol (usually TCP) and below an application protocol
(often HTTP). SSL is independent of the application it
encapsulates, and any higher level protocol can layer on top of
SSL transparently. However, many Internet applications might be
better served by IPsec.
SSL has two layers: (a) SSL's lower layer, the SSL Record
Protocol, is layered on top of the transport protocol and
encapsulates higher level protocols. One such encapsulated
protocol is SSL Handshake Protocol. (b) SSL's upper layer provides
asymmetric cryptography for server authentication (verifying the
server's identity to the client) and optional client
authentication (verifying the client's identity to the server),
and also enables them, before the application protocol transmits
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or receives data, to negotiate a symmetric encryption algorithm
and secret session key (to use for data confidentiality service)
and a keyed hash (to use for data integrity service).
$ secure state
1a. (I) A system condition in which the system is in conformance
with the applicable security policy. (Compare: clean system,
transaction.)
1b. (I) /formal model/ A system condition in which no subject can
access any object in an unauthorized manner. (See: (secondary
definition under) Bell-LaPadula model.)
$ security
1a. (I) A system condition that results from the establishment and
maintenance of measures to protect the system.
1b. (I) A system condition in which system resources are free from
unauthorized access and from unauthorized or accidental change,
destruction, or loss. (Compare: safety.)
2. (I) Measures taken to protect a system.
Tutorial: Providing a condition of system security may involve the
following six basic functions [Park]:
- "Avoidance": Reducing a risk by either reducing the value of
the potential loss or reducing the probability that the loss
will occur. (See: risk, risk analysis.)
- "Deterrence": Reducing an intelligent threat by discouraging
action, such as by fear or doubt. (See: attack, threat action.)
- "Prevention": Impeding a security violation by using a
countermeasure.
- "Detection": Determining that a security violation is
impending, is in progress, or has recently occurred, and thus
make it possible to reduce the potential loss. (See: intrusion
detection.)
- "Recovery": Restoring a normal state of system operation by
compensating for a security violation, possibly by eliminating
or repairing its effects. (See: contingency plan.)
- "Correction": Changing a security architecture to eliminate or
reduce the risk of reoccurrence of a security violation or
threat consequence.
$ security architecture
(I) A plan and set of principles that describe (a) the security
services that a system is required to provide to meet the needs of
its users, (b) the system components required to implement the
services, and (c) the performance levels required in the
components to deal with the threat environment. (See: defense in
depth, IATF, (Tutorial under) security policy. Compare: system
architecture.)
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Tutorial: A security architecture is the result of applying the
system engineering process. A complete system security
architecture includes administrative security, communication
security, computer security, emanations security, personnel
security, and physical security (e.g., see: [R2179]). A complete
security architecture needs to deal with both intentional,
intelligent threats and accidental threats.
$ Security Assertion Markup Language (SAML)
(N) A protocol consisting of XML-based request and response
message formats for exchanging security information, expressed in
the form of assertions about subjects, between online business
partners. [SAML]
$ security association
1. (I) A relationship established between two or more entities to
enable them to protect data they exchange. (See: association,
ISAKMP, SAD. Compare: session.)
Tutorial: The relationship is represented by a set of data that is
shared between the entities and is agreed upon and considered a
contract between them. The data describes how the associated
entities jointly use security services. The relationship is used
to negotiate characteristics of security mechanisms, but the
relationship is usually understood to exclude the mechanisms
themselves.
2. (O) "A set of policy and cryptographic keys that provide
security services to network traffic that matches that policy".
[R3740] (See: cryptographic association, group security
association.)
3. (O) /IPsec/ A simplex (uni-directional) logical connection
created for security purposes and implemented with either AH or
ESP (but not both). The security services offered by a security
association depend on the protocol (AH or ESP), the IPsec mode
(transport or tunnel), the endpoints, and the election of optional
services within the protocol. A security association is identified
by a triple consisting of (a) a destination IP address, (b) a
protocol (AH or ESP) identifier, and (c) a Security Parameter
Index.
4. (O) "The totality of communications and security mechanisms and
functions (e.g., communications protocols, security protocols,
security mechanisms and functions) that securely binds together
two security contexts in different end systems or relay systems
supporting the same information domain." [DGSA]
$ Security Association Database (SAD)
(I) In an IPsec implementation operating in a network node, a
database that contains parameters to describe the status and
operation of each of the active security associations that the
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node has established with other nodes. Separate inbound and
outbound SADs are needed because of the directionality of IPsec
security associations. [R2401] (Compare: SPD.)
$ security association identifier (SAID)
(I) A data field in a security protocol (such as NLSP or SDE),
used to identify the security association to which a protocol data
unit is bound. The SAID value is usually used to select a key for
decryption or authentication at the destination. (See: Security
Parameter Index.)
$ security assurance
1. (I) An attribute of an information system that provides grounds
for having confidence that the system operates such that the
system security policy is enforced. (Compare: trust.)
2. (I) A procedure that ensures a system is developed and operated
as intended by the system's security policy.
3. (D) "The degree of confidence one has that the security
controls operate correctly and protect the system as intended."
[SP12]
Deprecated Definition: ISDs SHOULD NOT use definition 3; it is a
definition for "assurance level" rather than for "assurance".
4. (D) /U.S. Government, identity authentication/ The (a) "degree
of confidence in the vetting process used to establish the
identity of the individual to whom the [identity] credential was
issued" and (b) "the degree of confidence that the individual who
uses the credential is the individual to whom the credential was
issued". [M0404]
Deprecated Definition: ISDs SHOULD NOT use definition 4; it mixes
concepts in a potentially misleading way. Part "a" is a definition
for "assurance level" (rather than "security assurance") of an
identity registration process; and part "b" is a definition for
"assurance level" (rather than "security assurance") of such a
process. Also, the processes of registration and authentication
should be defined and designed separately to ensure clarity in
certification.
$ security audit
(I) An independent review and examination of a system's records
and activities to determine the adequacy of system controls,
ensure compliance with established security policy and procedures,
detect breaches in security services, and recommend any changes
that are indicated for countermeasures. [I7498 Part 2, NCS01]
(Compare: accounting, intrusion detection.)
Tutorial: The basic audit objective is to establish accountability
for system entities that initiate or participate in security-
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relevant events and actions. Thus, means are needed to generate
and record a security audit trail and to review and analyze the
audit trail to discover and investigate attacks and security
compromises.
$ security audit trail
(I) A chronological record of system activities that is sufficient
to enable the reconstruction and examination of the sequence of
environments and activities surrounding or leading to an
operation, procedure, or event in a security-relevant transaction
from inception to final results. [NCS04] (See: security audit.)
$ security by obscurity
(O) Attempting to maintain or increase security of a system by
keeping secret the design or construction of a security mechanism.
Tutorial: This approach has long been discredited in cryptography,
where the phrase refers to trying to keep an algorithm secret,
rather than just concealing the keys [Schn]. One must assume that
mass-produced or widely fielded cryptographic devices eventually
will be lost or stolen and, therefore, that the algorithms will be
reverse engineered and become known to the adversary. Thus, one
should rely only on algorithms and protocols that are strong
enough to have been published widely, and have been peer reviewed
for long enough that their flaws have been found and removed. For
example, NIST used a long, public process to select AES to replace
DES.
In computer and network security, the principle of "no security by
obscurity" also applies to security mechanisms other than
cryptography. For example, if a protocol for access control, or
for identification and authentication, is really good, than
reading the protocol's source code should not enable you to find a
way to evade the protection and penetrate the system.
$ security class
(D) Synonym for "security level".
Deprecated Term: ISDs SHOULD NOT use this term. Instead, use
"security level", which is more widely established and understood.
$ security clearance
(I) A determination that a person is eligible, under the standards
of a specific security policy, for authorization to access
sensitive information or other system resources. (See: clearance
level.)
$ security compromise
(I) A security violation in which a system resource is exposed, or
is potentially exposed, to unauthorized access. (Compare: data
compromise, exposure, violation.)
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$ security doctrine
1. (I) A specified set of procedures or practices that direct or
provide guidance for how to comply with security policy. (Compare:
security mechanism, security policy.)
Tutorial: Security policy and security doctrine are relative
terms: policy deals mainly with strategy, and doctrine deals with
tactics.
Security doctrine is often understood to refer mainly to
administrative security, personnel security, and physical
security. For example, security mechanisms and devices that
implement them are normally designed to operate in a limited range
of environmental and administrative conditions, and these
conditions must be met to complement and ensure the technical
protection afforded by the hardware, firmware, and software in the
devices. Security doctrine specifies how to achieve those
conditions. (See: (first law under) Courtney's laws.)
$ security domain
(I) See: domain.
$ security environment
(I) The set of external entities, procedures, and conditions that
affect secure development, operation, and maintenance of a system.
(See: (first law under) Courtney's laws.)
$ security event
(I) A occurrence in a system that is relevant to the security of
the system. (See: security incident.)
Tutorial: The term covers both events that are security incidents
and those that are not. In a CA workstation, for example, a list
of security events might include the following:
- Logging the operator in or out.
- Performing a cryptographic operation, e.g., signing a digital
certificate or CRL.
- Performing a cryptographic card operation: creation, insertion,
removal, or backup.
- Performing a digital certificate lifecycle operation: rekey,
renewal, revocation, or update.
- Posting information to an X.500 Directory.
- Receiving a key compromise notification.
- Receiving an improper certification request.
- Detecting an alarm condition reported by a cryptographic
module.
- Failing a built-in hardware self-test or a software system
integrity check.
$ security fault analysis
(I) A security analysis, usually performed on hardware at a logic
gate level, gate-by-gate, to determine the security properties of
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a device when a hardware fault is encountered.
$ security gateway
1. (I) An internetwork gateway that separates trusted (or
relatively more trusted) hosts on one side from untrusted (or less
trusted) hosts on the other side. (See: firewall and guard.)
2. (O) /IPsec/ "An intermediate system that implements IPsec
protocols." [R2401]
Tutorial: IPsec's AH or ESP can be implemented on a gateway
between a protected network and an unprotected network, in order
to provide security services to the protected network's hosts when
they communicate across the unprotected network to other hosts and
gateways.
$ security incident
1. (I) A security event that involves a security violation. (See:
CERT, GRIP, security event, security intrusion. See: security
violation.)
Tutorial: In other words, a security-relevant system event in
which the system's security policy is disobeyed or otherwise
breached.
2. (O) "Any adverse event [that] compromises some aspect of
computer or network security." [R2350]
Deprecated Definition: ISDs SHOULD NOT use this "O" definition,
because (a) a security incident may occur without actually being
harmful (i.e., adverse) and (b) this Glossary defines "compromise"
more narrowly in relation to unauthorized access.
3. (O) "A violation or imminent threat of violation of computer
security policies, acceptable use policies, or standard computer
security practices." [SP61]
Deprecated Definition: ISDs SHOULD NOT use this "O" definition,
because mixes concepts in way that does not agree with common
usage; a security incident is commonly thought of as involving a
realization of a threat (see: threat action), not just a threat.
$ security intrusion
(I) A security event, or a combination of multiple security
events, that constitutes a security incident in which an intruder
gains, or attempts to gain, access to a system (or system
resource) without having authorization to do so.
$ security kernel
(I) "The hardware, firmware, and software elements of a trusted
computing base that implement the reference monitor concept. It
must mediate all accesses, be protected from modification, and be
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verifiable as correct." [NCS04] (See: kernel, TCB.)
Tutorial: A security kernel is an implementation of a reference
monitor for a given hardware base. [Huff]
$ security label
(I) An item of meta-data that designates the value of one or more
security-relevant attributes (e.g., security level) of a system
resource. (Compare: security marking. See: [R1457].)
Deprecated usage: To avoid confusion, ISDs SHOULD NOT use
"security label" for "security marking", or vice versa, even
though that is commonly done (including in some national and
international standards that should know better).
Tutorial: Humans and automated security mechanisms use a security
label of a system resource to determine, according to applicable
security policy, how to control access to the resource (and they
affix appropriate, matching security markings to physical
instances of the resource). Security labels are most often used to
support data confidentiality policy, and sometimes used to support
data integrity policy.
As explained in [R1457], the form that is taken by security labels
of a protocol's packets varies depending on the OSIRM layer in
which the protocol operates. Like meta-data generally, a security
label of a data packet may be either explicit (e.g., IPSO) or
implicit (e.g., Alice treats all messages received from Bob as
being labeled "Not For Public Release"). In a connectionless
protocol, every packet might have an explicit label; but in a
connection-oriented protocol, all packets might have the same
implicit label that is determined at the time the connection is
established.
Both classified and unclassified system resources may require a
security label. (See: FOUO.)
$ security level
(I) The combination of a hierarchical classification level and a
set of non-hierarchical category designations that represents how
sensitive a specified type or item of information is. (See:
(Deprecated Usage note under) classification level, dominate,
lattice model.)
Usage: The term is usually understood to refer to sensitivity to
disclosure, but also is used in many other ways and could easily
be misunderstood; therefore, ISDs that use this term SHOULD state
a definition for it.
$ Security Level field
(I) A 16-bit field (the "S field") that specifies a security level
value in the security option (option type 130) of version 4 IP's
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datagram header format.
Deprecated Abbreviation: ISDs SHOULD NOT use the abbreviation "S
field", which is potentially ambiguous. Instead, use "Security
Level field".
$ security management infrastructure (SMI)
(I) System components and activities that support security policy
by monitoring and controlling security services and mechanisms,
distributing security information, and reporting security events.
Tutorial: The associated functions are as follows [I7498-4]:
- Controlling (granting or restricting) access to system
resources: This includes verifying authorizations and
identities, controlling access to sensitive security data, and
modifying access priorities and procedures in the event of
attacks.
- Retrieving (gathering) and archiving (storing) security
information: This includes logging security events and
analyzing the log, monitoring and profiling usage, and
reporting security violations.
- Managing and controlling the encryption process: This includes
performing the functions of key management and reporting on key
management problems. (See: PKI.)
$ security marking
(I) A physical marking that is bound to an instance of a system
resource and that represents a security label of the resource,
i.e., that names or designates the value of one or more security-
relevant attributes of the resource. (Compare: security label.)
Tutorial: A security label may be represented by various
equivalent markings depending on the physical form taken by the
labeled resource. For example, a document could have a marking
composed of a bit pattern [FP188] when the document is stored
electronically as a file in a computer, and also a marking of
printed alphabetic characters when the document is in paper form.
$ security mechanism
(I) A process (or a device incorporating such a process) that can
be used in a system to implement a security service that is
provided by or within the system. (See: (discussion under)
security policy. Compare: security doctrine.)
Usage: Usually understood to refer primarily to components of
communication security, computer security, and emanation security.
Examples: Authentication exchange, checksum, digital signature,
encryption, and traffic padding.
$ security model
(I) A schematic description of a set of entities and relationships
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by which a specified set of security services are provided by or
within a system. Example: Bell-LaPadula model. (See: (discussion
under) security policy.)
$ security parameters index (SPI)
(I) /IPsec/ A 32-bit identifier used to distinguish among security
associations that terminate at the same destination (IP address)
and use the same security protocol (AH or ESP). Carried in AH and
ESP to enable the receiving system to determine under which
security association to process a received packet.
(I) /mobile IP/ A 32-bit index identifying a security association
between a pair of nodes, from among the collection of associations
between them that are available for application to mobile IP
protocol messages that they exchange.
$ security perimeter
(I) A physical or logical boundary that is defined for a domain or
enclave and within which a particular security policy or security
architecture applies. (See: insider, outsider.)
$ security policy
1a. (I) A set of security principles or rules that direct how a
system or organization provides security services to protect
sensitive and critical system resources. (See: identity-based
security policy, policy rule, rule-based security policy, rules of
behavior. Compare: security architecture, security doctrine,
security mechanism, security model, [R1281].)
1b. (O) /X.509/ A set of security rules laid down by an authority
to govern the use and provision of security services and
facilities.
2. (O) /Common Criteria/ A set of rules that regulate how assets
are managed, protected, and distributed within a TOE.
Tutorial: Ravi Sandhu notes that security policy is one of four
layers of the security engineering process (as shown in the
following diagram). Each layer provides a different view of
security, ranging from what services are needed to how services
are implemented. From a security architect~Os perspective, a
security policy is the requirements specification for designing an
adequately secure system.
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What Security Services Should Be Provided?
^
| + - - - - - - - - - - - +
| | Security Policy |
| + - - - - - - - - - - - + + - - - - - - - - - - - - - - +
| | Security Model | | A "top-level specification" |
| + - - - - - - - - - - - + <- | is at a level below "model" |
| | Security Architecture | | but above "architecture". |
| + - - - - - - - - - - - + + - - - - - - - - - - - - - - +
| | Security Mechanism |
| + - - - - - - - - - - - +
v
How Are Security Services Implemented?
Rob Shirey suggests that another way to think about Sandhu's
layers is to say that statements of security policy vary in their
degree of abstraction according to the perspectives of the
participants in system design, development, and operation
activities:
- Mission functions view: Has perspective of user of information
system resources. States time-phased protection needs for
system resources and identifies sensitive and critical
resources -- networks, hosts, applications, and databases.
Independent of rules and practices used to achieve protection.
- Domain practices view: Has perspective of enterprise manager
who sets protection standards for resources. States rules and
practices for protection. Identifies domain members; i.e.,
entities (users/providers) and resources (including data
objects). Independent of system topology. Not required to be
hierarchical.
- Enclave services view: Has perspective of system designer who
allocates security functions to major components. Assigns
security services to system topology structures and their
contents. Independent of security mechanisms. Hierarchical
across all domains.
- Agent mechanisms view: Has perspective of system engineer who
specifies security mechanisms to implement security services.
Specifies mechanisms to be used by protocol, database, and
application engines. Independent of type and manufacture of
platforms and other physical devices.
- Platform devices view: Has perspective of as-built description
of the system in operation. Specifies exactly how to build or
assemble the system, and also specifies procedures for
operating the system.
$ Security Policy Database (SPD)
(I) In an IPsec implementation operating in a network node, a
database that contains parameters that specify policies set by a
user or administrator to determine what IPsec services, if any,
are to be provided to IP datagrams sent or received by the node,
and in what fashion they are provided. For each datagram, the SPD
specifies one of three choices: discard the datagram, apply IPsec
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services (e.g., AH or ESP), or bypass IPsec. Separate inbound and
outbound SPDs are needed because of the directionality of IPsec
security associations. [R2401] (Compare: SAD.)
$ Security Protocol 3 (SP3)
(O) A protocol [SDNS3] developed by SDNS to provide connectionless
data security at the top of OSIRM layer 3. (Compare: IPsec, NLSP.)
$ Security Protocol 4 (SP4)
(O) A protocol [SDNS4] developed by SDNS to provide either
connectionless or end-to-end connection-oriented data security at
the bottom of OSIRM layer 4. (See: TLSP.)
$ security-relevant event
(D) See: security event.
$ security rule
(I) A building block of a security policy; it defines (a) a set of
system conditions and (b) a set of system actions that are to be
performed if those conditions occur. [R3198]
$ security service
1. (I) A processing or communication service that is provided by a
system to give a specific kind of protection to system resources.
(See: access control service, audit service, availability service,
data confidentiality service, data integrity service, data origin
authentication service, non-repudiation service, peer entity
authentication service, system integrity service.)
Tutorial: Security services implement security policies, and are
implemented by security mechanisms.
2. (O) "A service, provided by a layer of communicating open
systems, which ensures adequate security of the systems or the
data transfers." [I7498 Part 2]
$ security situation
(I) ISAKMP usage: The set of all security-relevant information --
e.g., network addresses, security classifications, manner of
operation (normal or emergency) -- that is needed to decide the
security services that are required to protect the association
that is being negotiated.
$ security target
(N) /Common Criteria/ A set of security requirements and
specifications to be used as the basis for evaluation of an
identified TOE.
Tutorial: An security target (ST) is a statement of security
claims for a particular information technology security product or
system, and is the basis for agreement among all parties as to
what security the product or system offers. An ST parallels the
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structure of an protection profile, but has additional elements
that include product-specific detailed information. An ST contains
a summary specification, which defines the specific measures taken
in the product or system to meet the security requirements.
$ security token
(I) See: token.
$ security violation
(I) An act or event that disobeys or otherwise breaches security
policy. (See: compromise, penetration, security incident.)
$ seed
(I) A value that is an input to a pseudorandom number generator.
$ self-signed certificate
(I) A public-key certificate for which the public key bound by the
certificate and the private key used to sign the certificate are
components of the same key pair, which belongs to the signer.
(Compare: root certificate.)
Tutorial: In a self-signed X.509 public-key certificate, the
issuer's DN is the same as the subject's DN.
$ semantic security
(I) An attribute of a encryption algorithm that is a formalization
of the notion that the algorithm not only hides the plain text but
also reveals no partial information about the plain text; i.e.,
whatever is computable about the plain text when given the cipher
text, is also computable without the cipher text. (Compare:
indistinguishability.)
$ semiformal
(I) Expressed in a restricted syntax language with defined
semantics. [CCIB] (Compare: formal, informal.)
$ sensitive compartmented information (SCI)
(O) /U.S. Government/ Classified information concerning or derived
from intelligence sources, methods, or analytical processes, which
is required to be handled within formal control systems
established by the Director of Central Intelligence. [DC6/9] (See:
SCIF)
$ sensitive compartmented information facility (SCIF)
(O) /U.S. Government/ An accredited area, room, group of rooms,
building, or installation where SCI may be stored, used,
discussed, or electronically processed. [DC6/9]
$ sensitive information
(I) Information for which (a) disclosure, (b) alteration, or (c)
destruction or loss could adversely affect the interests or
business of its owner or user. (See: data confidentiality, data
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integrity. Compare: classified, critical.)
(O) /U.S. Government/ Information for which (a) loss, (b) misuse,
(c) unauthorized access, or (d) unauthorized modification could
adversely affect the national interest or the conduct of federal
programs, or the privacy to which individuals are entitled under
the Privacy Act of 1974, but that has not been specifically
authorized under criteria established by an Executive Order or an
Act of Congress to be kept classified in the interest of national
defense or foreign policy.
Tutorial: Systems that are not U.S. national security systems, but
contain sensitive U.S. Federal Government information, must be
protected according to the Computer Security Act of 1987 (Public
Law 100-235).
$ sensitivity label
(D) Synonym for "classification label".
Deprecated term: ISDs should not use this term because the
definition of "sensitive" involves not only data confidentiality,
but also data integrity.
$ sensitivity level
(D) Synonym for "classification level".
Deprecated term: ISDs should not use this term because the
definition of "sensitive" involves not only data confidentiality,
but also data integrity.
$ separation of duties
(I) The practice of dividing the steps in a system function among
different individual entities (i.e., different users or different
roles) so as to keep a single entity from subverting the process.
Sometimes called "separation of privilege". (See: administrative
security, dual control.)
$ serial number
See: certificate serial number.
$ server
(I) A system entity that provides a service in response to
requests from other system entities called clients.
$ session
1a. (I) /computer usage/ A continuous period of time, usually
initiated by a login, during which a user accesses a computer
system.
1b. (I) /computer activity/ The set of transactions or other
computer activities that are performed by or for a user during a
period of computer usage.
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2. (I) /access control/ A temporary mapping of a principal to one
or more roles. (See: role-based access control.)
Tutorial: A user establishes a session as a principal and
activates some subset of roles to which the principal has been
assigned. The authorizations available to the principal in the
session are the union of permissions from all the roles activated
in the session. Each session is associated with a single principal
and, therefore, with a single user. A principal may have multiple,
concurrent sessions and may activate a different set of roles in
each session.
3. (I) /computer network/ A persistent but (normally) temporary
association between a user agent (typically a client) and a second
process (typically a server). The association may persist across
multiple exchanges of data, including multiple connections.
(Compare: security association.)
$ session key
(I) In the context of symmetric encryption, a key that is
temporary or is used for a relatively short period of time. (See:
ephemeral key, KDC, session. Compare: master key.)
Tutorial: A session key is used for a defined period of
communication between two system entities or components, such as
for the duration of a single connection or transaction set; or the
key is used in an application that protects relatively large
amounts of data and, therefore, needs to be rekeyed frequently.
$ SET
(O) See: SET Secure Electronic Transaction(trademark).
$ SET private extension
(O) One of the private extensions defined by SET for X.509
certificates. Carries information about hashed root key,
certificate type, merchant data, cardholder certificate
requirements, encryption support for tunneling, or message support
for payment instructions.
$ SET qualifier
(O) A certificate policy qualifier that provides information about
the location and content of a SET certificate policy.
Tutorial: In addition to the policies and qualifiers inherited
from its own certificate, each CA in the SET certification
hierarchy may add one qualifying statement to the root policy when
the CA issues a certificate. The additional qualifier is a
certificate policy for that CA. Each policy in a SET certificate
may have these qualifiers: (a) a URL where a copy of the policy
statement may be found; (b) an electronic mail address where a
copy of the policy statement may be found; (c) a hash result of
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the policy statement, computed using the indicated algorithm; and
(d) a statement declaring any disclaimers associated with the
issuing of the certificate.
$ SET Secure Electronic Transaction(trademark) or SET(trademark)
(N) A protocol developed jointly by MasterCard International and
Visa International and published as an open standard to provide
confidentiality of transaction information, payment integrity, and
authentication of transaction participants for payment card
transactions over unsecured networks, such as the Internet. [SET1]
(See: acquirer, brand, cardholder, dual signature, electronic
commerce, IOTP, issuer, merchant, payment gateway, third party.)
Tutorial: This term and acronym are trademarks of SETCo.
MasterCard and Visa announced the SET standard on 1 February 1996.
$ SETCo
(O) Abbreviation for "SET Secure Electronic Transaction LLC",
formed on 19 December 1997 by MasterCard and Visa for the purpose
of implementing the SET Secure Electronic Transaction" standard.
A memorandum of understanding adds American Express and JCB Credit
Card Company as co-owners of SETCo.
$ SHA, SHA-1, SHA-2
(N) See: Secure Hash Algorithm.
$ shared identity
(I) See: (secondary definition under) identity.
$ shared secret
(D) A synonym for "cryptographic key" or "password".
Deprecated Usage: The term is used in many ways and could easily
be misunderstood; therefore, ISDs that use this term SHOULD state
a definition for it.
$ shielded enclosure
(O) "Room or container designed to attenuate electromagnetic
radiation." [C4009] (See: emanation.)
$ short title
(O) "Identifying combination of letters and numbers assigned to
certain items of COMSEC material to facilitate handling,
accounting, and controlling." [C4009] (Compare: KMID, long title.)
$ SHS
(N) See: Secure Hash Standard.
$ sign
(I) Create a digital signature for a data object. (See: signer.)
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$ signal analysis
(I) Gaining indirect knowledge (inference) of communicated data by
monitoring and analyzing a signal that is emitted by a system and
that contains the data but is not intended to communicate the
data. (See: emanation. Compare: traffic analysis.)
$ signal intelligence
(I) The science and practice of extracting information from
signals. (See: signal security.)
$ signal security
(N) (I) The science and practice of protecting signals. (See:
cryptology, security.)
Tutorial: The term "signal" denotes communication in almost any
form and also impulses emitted for other purposes, such as radar.
Signal security is opposed by signal intelligence, and each
discipline includes opposed sub-disciplines as follows [Kahn]:
Signal Security Signal Intelligence
------------------------------ ---------------------------------
1. Communication Security 1. Communication Intelligence
1a. Cryptography 1a. Cryptanalysis
1b. Traffic Security 1b. Traffic Analysis
1c. Steganography 1c. Detection and Interception
2. Electronic Security 2. Electronic Intelligence
2a. Emission Security 2a. Electronic Reconnaissance
2b. Counter-Countermeasures 2b. Countermeasures
------------------------------ ---------------------------------
$ signature
(O) A symbol or process adopted or executed by a system entity
with present intention to declare that a data object is genuine.
(See: digital signature, electronic signature.)
$ signature certificate
(I) A public-key certificate that contains a public key that is
intended to be used for verifying digital signatures, rather than
for encrypting data or performing other cryptographic functions.
Tutorial: A v3 X.509 public-key certificate may have a "keyUsage"
extension that indicates the purpose for which the certified
public key is intended. (See: certificate profile.)
$ signed receipt
(I) An S/MIME service [R2634] that (a) provides, to the originator
of a message, proof of delivery of the message and (b) enables the
originator to demonstrate to a third party that the recipient was
able to verify the signature of the original message.
Tutorial: The receipt is bound to the original message by a
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signature; consequently, the service may be requested only for a
message that is signed. The receipt sender may optionally also
encrypt the receipt to provide confidentiality between the receipt
sender and the receipt recipient.
$ signer
(N) A human being or organization entity that uses a private key
to sign (i.e., create a digital signature on) a data object. [ABA]
$ SILS
(N) See: Standards for Interoperable LAN/MAN Security.
$ simple authentication
1. (I) An authentication process that uses a password as the
information needed to verify an identity claimed for an entity.
(Compare: strong authentication.)
2. (O) "Authentication by means of simple password arrangements."
[X509]
$ Simple Authentication and Security Layer (SASL)
(I) An Internet specification [R2222] for adding authentication
service to connection-based protocols.
Tutorial: To use SASL, a protocol includes a command for
authenticating a user to a server and for optionally negotiating
protection of subsequent protocol interactions. The command names
a registered security mechanism. SASL mechanisms include Kerberos,
GSSAPI, S/KEY, and others. Some protocols that use SASL are IMAP4
and POP3.
$ Simple Key Management for Internet Protocols (SKIP)
(I) A key distribution protocol that uses hybrid encryption to
convey session keys that are used to encrypt data in IP packets.
Tutorial: SKIP was designed by Ashar Aziz and Whitfield Diffie at
Sun Microsystems and proposed as the standard key management
protocol for IPsec, but IKE was chosen instead. Although IKE is
mandatory for an IPsec implementation, the use of SKIP is not
excluded.
SKIP uses the Diffie-Hellman algorithm (or could use another key
agreement algorithm) to generate a key-encrypting key for use
between two entities. A session key is used with a symmetric
algorithm to encrypt data in one or more IP packets that are to be
sent from one entity to the other. A symmetric KEK is established
and used to encrypt the session key, and the encrypted session key
is placed in a SKIP header that is added to each IP packet that is
encrypted with that session key.
$ Simple Mail Transfer Protocol (SMTP)
(I) A TCP-based, application-level, Internet Standard protocol
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(RFC 821) for moving electronic mail messages from one computer to
another.
$ Simple Network Management Protocol (SNMP)
(I) A TCP-based, application-level, Internet Standard protocol
[R2570, R2574] for conveying management information between
managers and agents.
$ Simple Public Key Infrastructure (SPKI)
(I) A set of experimental concepts (RFCs 2692, 2693) that were
proposed as alternatives to the concepts standardized in PKIX.
$ simple security property
(N) /formal model/ Property of a system whereby a subject has
read access to an object only if the clearance of the subject
dominates the classification of the object. See: Bell-LaPadula
model.
$ single sign-on
(I) A system that enables a user to access multiple computer
platforms (usually a set of hosts on the same network) or multiple
application systems after being authenticated just one time. (See:
Kerberos.)
Tutorial: In a single sign-on system, a user typically logs in
just once, and then is transparently granted access to a set of
system resources with no further login being required (unless, of
course, the user logs out). Such a system has the advantages of
being user friendly and enabling authentication to be managed
consistently across an entire enterprise. Such a system also has
the disadvantage of requiring all hosts and applications to trust
the same authentication information.
$ singular identity
(I) See: (secondary definition under) identity.
$ site
(I) A facility--i.e., a physical space, room, or building together
with its physical, personnel, administrative, and other
safeguards--in which system functions are performed. (See: node.)
$ situation
See: security situation.
$ SKEME
(I) A key distribution protocol from which features were adapted
for IKE. [SKEME]
$ SKIP
(I) See: Simple Key-management for IP.
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$ SKIPJACK
(N) A type 2 block cipher [SKIP, R2773] with a block size of 64
bits and a key size of 80 bits. (See: CAPSTONE, CLIPPER, FORTEZZA,
Key Exchange Algorithm.)
Tutorial: SKIPJACK was developed by NSA and formerly classified at
the U.S. DoD "Secret" level. On 23 June 1998, NSA announced that
SKIPJACK had been declassified.
$ slot
(O) /MISSI/ One of the FORTEZZA PC card storage areas that are
each able to hold an X.509 certificate plus other data, such as
the private key that is associated with a public-key certificate.
$ smart card
(I) A credit-card sized device containing one or more integrated
circuit chips, which perform the functions of a computer's central
processor, memory, and input/output interface. (See: PC card.)
Usage: Sometimes this term is used rather strictly to mean a card
that closely conforms to the dimensions and appearance of the kind
of plastic credit card issued by banks and merchants. At other
times, the term is used loosely to include cards that are larger
than credit cards, especially cards that are thicker, such as PC
cards.
Tutorial: A "smart token" is a device that conforms to the
definition of smart card except that rather than having standard
credit card dimensions, the token is packaged in some other form,
such as a dog tag or door key shape.
$ smart token
See: (secondary definition under) smart card.
$ SMI
(I) See: security management infrastructure.
$ SMTP
(I) See: Simple Mail Transfer Protocol.
$ smurf attack
(D) A denial-of-service attack that uses IP broadcast addressing
to send ICMP ping packets with the intent of flooding a system.
(See: ICMP flood.)
Deprecated Term: ISDs SHOULD NOT use this term. It is not listed
in most dictionaries, and it is likely that other cultures have
different metaphors for this concept. (The Smurfs are a fictional
race of many small blue creatures that were created by a
cartoonist. Perhaps the inventor of this attack thought that a
swarm of ping packets resembled a group of smurfs.) (See:
(Deprecated Usage under) Green Book.)
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Tutorial: The attacker sends ICMP echo request ("ping") packets
that appear to originate not from the attacker's own IP address,
but from the address of the host or router that is target of the
attack. Each packet is addressed to an IP broadcast address, e.g.,
to all IP addresses in a given network. Thus, each echo request
that is sent by the attacker results in many echo responses being
sent to the target address. This attack can disrupt service at a
particular host, at the hosts that depend on a particular router,
or in an entire network.
$ sneaker net
(D) A process that transfers data between systems only manually,
under human control; i.e., a data transfer process that involves
an air gap.
Deprecated Term: ISDs SHOULD NOT use this term. It is not listed
in most dictionaries, and it is likely that other cultures have
different metaphors for this concept.
$ Snefru
(N) A public-domain, cryptographic hash function (also called "The
Xerox Secure Hash Function") designed by Ralph C. Merkle at Xerox
Corporation. Snefru can produce either a 128-bit or 256-bit output
(i.e., hash result). [Schn] (See: Khafre, Khufu.)
$ sniffing
(D) Synonym for "passive wiretapping". (See: password sniffing.)
Deprecated Term: ISDs SHOULD NOT use this term; it unnecessarily
duplicates the meaning of a term that is better established. (See:
(Deprecated Usage under) Green Book.
$ SNMP
(I) See: Simple Network Management Protocol.
$ social engineering
(D) A euphemism for non-technical or low-technology methods used
to attack information systems.
Deprecated Term: ISDs SHOULD NOT use this term; it is too vague.
Instead, use a term that is specific with regard to the means of
attack, e.g., lies, impersonation, tricks, bribes, blackmail, and
threats.
$ SOCKS
(I) An Internet protocol [R1928] that provides a generalized proxy
server that enables client-server applications -- such as TELNET,
FTP, and HTTP; running over either TCP or UDP -- to use the
services of a firewall.
Tutorial: SOCKS is layered under the IPS application layer and
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above the transport layer. When a client inside a firewall wishes
to establish a connection to an object that is reachable only
through the firewall, it uses TCP to connect to the SOCKS server,
negotiates with the server for the authentication method to be
used, authenticates with the chosen method, and then sends a relay
request. The SOCKS server evaluates the request, typically based
on source and destination addresses, and either establishes the
appropriate connection or denies it.
$ soft TEMPEST
(O) The use of software techniques to reduce the radio frequency
information leakage from computer displays and keyboards. [Kuhn]
(See: TEMPEST.)
$ software
(I) Computer programs (which are stored in and executed by
computer hardware) and associated data (which also is stored in
the hardware) that may be dynamically written or modified during
execution. (See: firmware, hardware.)
$ SORA
(O) See: SSO-PIN ORA.
$ source authentication
(D) Deprecated Term: ISDs SHOULD NOT use this term; it is
ambiguous. If the intent is to authenticate the original creator
or packager of data received, then say "data origin
authentication". If the intent is to authenticate the identity of
the sender of data, then say "peer entity authentication". (See:
data origin authentication, peer entity authentication).
$ source integrity
(I) The degree of confidence that can be placed in information
based on the trustworthiness of its sources. (See: integrity.)
$ SP3
(O) See: Security Protocol 3.
$ SP4
(O) See: Security Protocol 4.
$ spam, SPAM(trademark)
1a. (I) /verb/ To indiscriminately send unsolicited, unwanted,
irrelevant, or inappropriate messages, especially commercial
advertising in mass quantities.
1b. (I) /noun/ Electronic "junk mail". [R2635]
Deprecated Usage: ISDs SHOULD NOT use this term in upper-case
letters, because SPAM(trademark) is a trademark of Hormel Foods
Corporation. Hormel says, "We do not object to use of this slang
term [spam] to describe [unsolicited advertising email], although
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we do object to the use of our product image in association with
that term. Also, if the term is to be used, it should be used in
all lower-case letters to distinguish it from our trademark SPAM,
which should be used with all uppercase letters." (See: metadata.)
Tutorial: In sufficient volume, spam can cause denial of service.
(See: flooding.) According to Hormel, the term was adopted as a
result of a Monty Python skit in which a group of Vikings sang a
chorus of 'SPAM, SPAM, SPAM ...' in an increasing crescendo,
drowning out other conversation. This lyric became a metaphor for
the unsolicited advertising messages that threaten to overwhelm
other discourse on the Internet.
$ SPD
(I) See: Security Policy Database.
$ special access program (SAP)
(O) /U.S. Government/ "[A kind of p]rogram [that is] established
for a specific class of classified information [and] that imposes
safeguarding and access requirements that exceed those normally
required for information at the same classified level." [C4009]
$ SPI
(I) See: Security Parameters Index.
$ SPKI
(I) See: Simple Public Key Infrastructure.
$ split key
(I) A cryptographic key that is divided into two or more separate
data items that individually convey no knowledge of the whole key
that results from combining the items. (See: dual control, split
knowledge.)
$ split knowledge
1. (I) A security technique in which two or more entities
separately hold data items that individually convey no knowledge
of the information that results from combining the items. (See:
dual control, split key.)
2. (O) "A condition under which two or more entities separately
have key components which individually convey no knowledge of the
plaintext key which will be produced when the key components are
combined in the cryptographic module." [FP140]
$ spoofing attack
(I) Synonym for "masquerade attack".
$ spread spectrum
1. (N) A TRANSEC technique that transmits a signal in a bandwidth
much greater than the transmitted information needs. [F1037]
Example: frequency hopping.
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Tutorial: Usually uses a sequential noise-like signal structure to
spread the normally narrowband information signal over a
relatively wide band of frequencies. The receiver correlates the
signals to retrieve the original information signal. This
technique decreases potential interference to other receivers,
while achieving data confidentiality and increasing immunity of
spread spectrum receivers to noise and interference.
$ spyware
(I) Software that an intruder has installed surreptitiously on a
networked computer to gather data from that computer and send it
through the network to the intruder or some other interested
party. (See: malicious logic, Trojan horse.)
Deprecated Usage: The term is used in many ways and could easily
be misunderstood; therefore, ISDs that use this term SHOULD state
a definition for it.
Tutorial: Some examples of the types of data that might be
gathered by spyware are application files, passwords, email
addresses, usage histories, and keystrokes. Some examples of
motivations for gathering the data are blackmail, financial fraud,
identity theft, industrial espionage, market research, and
voyeurism.
$ SSH(trademark)
(N) See: Secure Shell(trademark).
$ SSL
(I) See: Secure Sockets Layer.
$ SSO
(I) See: system security officer.
$ SSO PIN
(O) /MISSI/ One of two personal identification numbers that
control access to the functions and stored data of a FORTEZZA PC
card. Knowledge of the SSO PIN enables the card user to perform
the FORTEZZA functions intended for use by an end user and also
the functions intended for use by a MISSI CA. (See: user PIN.)
$ SSO-PIN ORA (SORA)
(O) /MISSI/ A MISSI organizational RA that operates in a mode in
which the ORA performs all card management functions and,
therefore, requires knowledge of the SSO PIN for FORTEZZA PC cards
issued to end users.
$ Standards for Interoperable LAN/MAN Security (SILS)
1. (N) The IEEE 802.10 standards committee. (See: FP191.)
2. (N) A set of IEEE standards, which has eight parts: (a) Model,
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including security management, (b) Secure Data Exchange protocol,
(c) Key Management, (d) [has been incorporated in (a)], (e) SDE
Over Ethernet 2.0, (f) SDE Sublayer Management, (g) SDE Security
Labels, and (h) SDE PICS Conformance. Parts b, e, f, g, and h are
incorporated in IEEE Standard 802.10-1998.
$ star property
(N) See: *-property.
$ Star Trek attack
(D) An attack that penetrates your system where no attack has ever
gone before.
Deprecated Usage: This is a joke for Trekkies. (See: (Deprecated
Usage under) Green Book.)
$ static
(I) /adjective/ Refers to a cryptographic key or other parameter
that is relatively long-lived. (Compare: ephemeral.)
$ steganography
(I) Methods of hiding the existence of a message or other data.
This is different than cryptography, which hides the meaning in a
message but does not hide the message itself. Example: "Invisible"
ink. (See: cryptology. Compare: digital watermarking.)
$ storage channel
See: covert storage channel.
$ stream cipher
(I) An encryption algorithm that breaks plain text into a stream
of successive elements (usually, bits) and encrypts the n-th
plaintext element with the n-th element of a parallel key stream,
thus converting the plaintext stream into a ciphertext stream.
[Schn] (See: block cipher.)
$ strength
(I) /COMPUSEC/ A rating of effectiveness of a security mechanism,
stated in terms of the minimum effort believed to be needed to
defeat the mechanism. (See: entropy, strong, work factor.)
$ strength of function
(N) /Common Criteria/ "A qualification of a TOE security function
expressing the minimum efforts assumed necessary to defeat its
expected security behavior by directly attacking its underlying
security mechanisms": (See: strength, strong.)
- Basic: "A level of the TOE strength of function where analysis
shows that the function provides adequate protection against
casual breach of TOE security by attackers possessing a low
attack potential."
- Medium: "... against straightforward or intentional breach ...
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by attackers possessing a moderate attack potential.
- High: "... against deliberately planned or organized breach ...
by attackers possessing a high attack potential."
$ strong
1. (I) /COMPUSEC/ Used to describe a security mechanism that would
be difficult to defeat. (See: strength.)
2. (I) /cryptography/ Used to describe a cryptographic algorithm
that would require a large amount of computational power to defeat
it. (See: work factor.)
$ strong authentication
1. (I) An authentication process that uses a cryptographic
security mechanism -- particularly public-key certificates -- to
verify the identity claimed for an entity. (Compare: simple
authentication.)
2. (O) "Authentication by means of cryptographically derived
credentials." [X509]
$ subject
1a. (I) A process in a computer system that represents a principal
and that executes with the privileges that have been granted to
that principal. (Compare: principal, user.)
1b. (I) /formal model/ A system entity that causes information to
flow among objects or changes the system state; technically, a
process-domain pair. A subject may itself be an object relative to
some other subject; thus, the set of subjects in a system is a
subset of the set of objects. (See: Bell-LaPadula model, object.)
2. (I) /digital certificate/ The entity name that is bound to the
data items in a digital certificate, and particularly a name that
is bound to a key in a public-key certificate. (See: X.509.)
$ subject CA
(D) The CA that is the subject of a cross-certificate issued by
another CA. [X509] (See: cross-certification.)
Deprecated Term: ISDs SHOULD NOT use this term because it is not
widely known and could be misunderstood. Instead, say "the CA that
is the subject of the cross-certificate".
$ subnetwork
(N) An OSI term for a system of packet relays and connecting links
that implement OSIRM layers 2 or 3 to provide a communication
service that interconnects attached end systems. Usually, the
relays are all of the same type (e.g., X.25 packet switches, or
interface units in an IEEE 802.3 LAN). (See: gateway, internet,
router.)
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$ subordinate CA (SCA)
1. (I) A CA whose public-key certificate is issued by another
(superior) CA. (See: certification hierarchy. Compare: cross-
certification.)
2. (O) /MISSI/ The fourth-highest (i.e., bottom) level of a MISSI
certification hierarchy; a MISSI CA whose public-key certificate
is signed by a MISSI CA rather than by a MISSI PCA. A MISSI SCA is
the administrative authority for a subunit of an organization,
established when it is desirable to organizationally distribute or
decentralize the CA service. The term refers both to that
authoritative office or role, and to the person who fills that
office. A MISSI SCA registers end users and issues their
certificates and may also register ORAs, but may not register
other CAs. An SCA periodically issues a CRL.
$ subordinate DN
(I) An X.500 DN is subordinate to another X.500 DN if it begins
with a set of attributes that is the same as the entire second DN
except for the terminal attribute of the second DN (which is
usually the name of a CA). For example, the DN <C=FooLand, O=Gov,
OU=Treasurer, CN=DukePinchpenny> is subordinate to the DN
<C=FooLand, O=Gov, CN=KingFooCA>.
$ subscriber
(I) /PKI/ A user that is registered in a PKI and, therefore, can
be named in the "subject" field of a certificate issued by a CA in
that PKI. (See: registration, user.)
Usage: This term is needed to distinguish registered users from
two other kinds of PKI users:
- Users that access the PKI but are not identified to it. For
example a relying party may access a PKI repository to obtain
the certificate of some other party. (See: access)
- Users that does not access the PKI. For example, a relying
party (see: certificate user) may use a digital certificate
that was obtained from a database that is not part of the PKI
that issued the certificate.
$ substitution
(I) /cryptography/ A method of encryption in which elements of the
plain text retain their original sequence but are replaced by
other elements. (Compare: transposition.)
$ subsystem
(I) A collection of related system components that together
perform a system function or deliver a system service.
$ superencryption
(I) An encryption operation for which the plaintext input to be
transformed is the ciphertext output of a previous encryption
operation. (Compare: hybrid encryption.)
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$ survivability
(I) The ability of a system to remain in operation or existence
despite adverse conditions, including both natural occurrences,
accidental actions, and attacks on the system. (Compare:
availability, reliability.)
$ swIPe
(I) An encryption protocol for IP that provides confidentiality,
integrity, and authentication and can be used for both end-to-end
and intermediate-hop security. [Ioan] (Compare: IPsec.)
Tutorial: The swIPe protocol is an IP predecessor that is
concerned only with encryption mechanisms; policy and key
management are handled outside the protocol.
$ syllabary
(N) /encryption/ A list of individual letters, combinations of
letters, or syllables, with their equivalent code groups, used for
spelling out proper names or other unusual words that are not
present in the basic vocabulary (i.e., are not in the codebook) of
a code used for encryption.
$ symmetric cryptography
(I) A branch of cryptography in which the algorithms use the same
key for both of two counterpart cryptographic operations (e.g.,
encryption and decryption). (See: asymmetric cryptography.
Compare: secret-key cryptography.)
Tutorial: Symmetric cryptography has been used for thousands of
years [Kahn]. A modern example is AES.
Symmetric cryptography has a disadvantage compared to asymmetric
cryptography with regard to key distribution. For example, when
Alice wants to ensure confidentiality for data she sends to Bob,
she encrypts the data with a key, and Bob uses the same key to
decrypt. However, keeping the shared key secret entails both cost
and risk when the key is distributed to both Alice and Bob. (See:
key management system.)
$ symmetric key
(I) A cryptographic key that is used in a symmetric cryptographic
algorithm. (See: symmetric cryptography.)
$ SYN flood
(I) A denial-of-service attack that sends a large number of TCP
SYN (synchronize) packets to a host with the intent of disrupting
the operation of that host. (See: flooding.)
Tutorial: This attack seeks to exploit a vulnerability in the TCP
specification or in a TCP implementation. Normally, two hosts use
a three-way exchange of packets to establish a TCP connection: (a)
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host 1 requests a connection by sending a SYN packet to host 2;
(b) host 2 replies by sending a SYN-ACK (acknowledgement) packet
to host 1; and (c) host 1 completes the connection by sending an
ACK packet to host 2. To attack host 2, host 1 can send a series
of TCP SYNs, each with a different phony source address. ([R2267]
discusses how to use packet filtering to prevent such attacks from
being launched from behind an Internet service provider's
aggregation point.) Host 2 treats each SYN as a request from a
separate host, replies to each with a SYN-ACK, and waits to
receive the matching ACKs. (The attacker can use random or
unreachable sources addresses in the SYN packets, or can use
source addresses that belong to third parties, that then become
secondary victims.)
For each SYN-ACK that is sent, the TCP process in host 2 needs
some memory space to store state information while waiting for the
matching ACK to be returned. If the matching ACK never arrives at
host 2, a timer associated with the pending SYN-ACK will
eventually expire and release the space. But if host 1 (or a
cooperating group of hosts) can rapidly send many SYNs to host 2,
host 2 will need to store state information for many pending SYN-
ACKs and may run out of space. This can prevent host 2 from
responding to legitimate connection requests from other hosts or
even, if there are flaws in host 2's TCP implementation, crash
when the space is exhausted.
$ synchronization
(I) Any technique by which a receiving (decrypting) cryptographic
process attains an internal state that matches the transmitting
(encrypting) process, i.e., has the appropriate keying material to
process the cipher text and is correctly initialized to do so.
$ system
Usage: In this Glossary, the term is mainly used as an
abbreviation for "information system". (See: subsystem.)
$ system architecture
(N) The structure of system components, their relationships, and
the principles and guidelines governing their design and evolution
over time. [DoDAF1] (Compare: security architecture.)
$ system component
1. (I) A collection of system resources that (a) forms a physical
or logical part of the system, (b) has specified functions and
interfaces, and (c) is treated (e.g., by policies or requirement
statements) as existing independently of other parts of the
system. (See: subsystem.)
2. (O) /ITSEC/ An identifiable and self-contained part of a TOE.
Usage: Component is a relative term because components may be
nested; i.e., one component of system may be a part of another
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component of that system.
Tutorial: Components can be characterized as follows:
- A "physical component" has mass and takes up space.
- A "logical component" is an abstraction used to manage and
coordinate aspects of the physical environment, and typically
represents a set of states or capabilities of the system.
$ system entity
(I) An active component of a system -- e.g., an automated process
or set of processes (see: subsystem), or a person or set of
persons (e.g., an organization) -- that incorporates a specific
set of capabilities. (Compare: subject, user.)
$ system high
(I) The highest security level at which a system operates, or is
capable of operating, at a particular time or in a particular
environment. (See: system high security mode.)
$ system high security mode
(I) A mode of operation of an information system, wherein all
users having access to the system possess a security clearance or
authorization, but not necessarily a need-to-know, for all data
handled by the system. (See: (system operation) mode.)
Usage: This mode was defined formally in U.S. DoD policy that
applied to system accreditation [DoD2], but the term is widely
used outside the Defense Department and outside the Government.
$ system integrity
(I) "The quality that a system has when it can perform its
intended function in a unimpaired manner, free from deliberate or
inadvertent unauthorized manipulation." [NCS04] (See: recovery,
system integrity service.)
$ system integrity service
(I) A security service that protects system resources in a
verifiable manner against unauthorized or accidental change, loss,
or destruction. (See: system integrity.)
$ system low
(I) The lowest security level supported by a system at a
particular time or in a particular environment. (See: system
high.)
$ system resource
(I) Data contained in an information system; or a service provided
by a system; or a system capability, such as processing power or
communication bandwidth; or an item of system equipment (i.e.,
hardware, firmware, software, or documentation); or a facility
that houses system operations and equipment. (See: system
component.)
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$ system security officer (SSO)
(I) A person responsible for enforcement or administration of the
security policy that applies to the system.
$ TACACS
(I) See: Terminal Access Controller (TAC) Access Control System.
$ TACACS+
(I) A TCP-based protocol that improves on TACACS and XTACACS by
separating the functions of authentication, authorization, and
accounting and by encrypting all traffic between the network
access server and authentication server. TACACS+ is extensible to
allow any authentication mechanism to be used with TACACS+
clients. (See: TACACS, XTACACS.)
$ tamper
(I) Make an unauthorized modification in a system that alters the
system's functioning in a way that degrades the security services
that the system was intended to provide. (See: QUADRANT. Compare:
(secondary definitions under) "corruption" and "misuse".)
$ tamper-evident
(I) A characteristic of a system component that provides evidence
that an attack has been attempted on that component or system.
Usage: Normally refers to physical evidence. (See: tamper.)
$ tamper-resistant
(I) A characteristic of a system component that provides passive
protection against an attack. (See: tamper.)
Usage: Normally refers to physical means of protection.
$ target of evaluation (TOE)
(N) /Common Criteria/ An information technology product or system
that is the subject of a security evaluation, together with the
product's associated administrator and user documentation.
Tutorial: The security characteristics of the target of evaluation
(TOE) are described in specific terms by a corresponding security
target, or in more general terms by a protection profile. In
Common Criteria philosophy, it is important that a TOE be
evaluated against the specific set of criteria expressed in the
security target (ST). This evaluation consists of rigorous
analysis and testing performed by an accredited, independent
laboratory. The scope of a TOE evaluation is set by the EAL and
other requirements specified in the ST. Part of this process is an
evaluation of the ST itself, to ensure that it is correct,
complete, and internally consistent and can be used as the
baseline for the TOE evaluation.
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$ TCB
(N) See: trusted computing base.
$ TCC field
(I) See: Transmission Control Code field.
$ TCP
(I) See: Transmission Control Protocol.
$ TCP/IP
(I) Synonym for "Internet Protocol Suite", in which the
Transmission Control Protocol (TCP) and the Internet Protocol (IP)
are important parts.
$ TCSEC
(N) See: Trusted Computer System Evaluation Criteria. (Compare:
TSEC.)
$ TDEA
(I) See: Triple Data Encryption Algorithm.
$ teardrop attack
(D) An denial-of-service attack that sends improperly formed IP
packet fragments with the intent of causing the destination system
to fail.
Deprecated Term: The term is often used imprecisely and could
easily be misunderstood; therefore, ISDs that use this term SHOULD
state a definition for it. (See: (Deprecated Usage under) Green
Book.)
$ technical non-repudiation
(I) See: (secondary definition under) non-repudiation.
$ technical security
(I) Security mechanisms and procedures that are implemented in and
executed by hardware, software, or firmware (rather than by
people) to provide automated protection for a system. (See:
security architecture. Compare: administrative security.)
$ Telecommunications Security Nomenclature System (TSEC)
(O) An NSA designation system for telecommunication security
equipment. (Compare: TCSEC.)
Tutorial: A TSEC designator has the following parts:
- Prefix "TSEC/" for items and systems, or suffix "/TSEC" for
assemblies. (Often omitted when the context is clear.)
- First letter, for function: "C" COMSEC equipment system, "G"
general purpose, "K" cryptographic, "H" crypto-ancillary, "M"
manufacturing, "N" noncryptographic, "S" special purpose.
- Second letter, for type or purpose: "G" key generation, "I"
data transmission, "L" literal conversion, "N" signal
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conversion, "O" multipurpose, "P" materials production, "S"
special purpose, "T" testing or checking, "U" television, "W"
teletypewriter, "X" facsimile, "Y" speech.
- Optional third letter, used only in designations of assemblies,
for type or purpose: "A" advancing, "B" base or cabinet, "C"
combining, "D" drawer or panel, "E" strip or chassis, "F" frame
or rack, "G" key generator, "H" keyboard, "I" translator or
reader, "J" speech processing, "K" keying or permuting, "L"
repeater, "M" memory or storage, "O" observation, "P" power
supply or converter, "R" receiver, "S" synchronizing, "T"
transmitter, "U" printer, "V" removable COMSEC component, "W"
logic programmer/programming, "X" special purpose.
- Model number, usually two or 3 digits, assigned sequentially
within each letter combination (e.g., KG-34, KG-84).
- Optional suffix letter, used to designate a version. First
version has no letter, next version has "A" (e.g., KG-84, KG-
84A), etc.
$ TELNET
(I) A TCP-based, application-level, Internet Standard protocol
(RFC 854) for remote login from one host to another.
$ TEMPEST
(N) Short name for technology and methods for protecting against
data compromise due to electromagnetic emanations from electrical
and electronic equipment. [Russ] (See: inspectable space, soft
TEMPEST, TEMPEST zone. Compare: QUADRANT)
(O) /U.S. Government/ "Short name referring to investigation,
study, and control of compromising emanations from IS equipment."
[N4009]
Deprecated Usage: ISDs SHOULD NOT use this term as a synonym for
"electromagnetic emanations security"; instead, use EMSEC. Also,
the term is NOT an acronym for Transient Electromagnetic Pulse
Surveillance Technology.
Tutorial: U.S. Government security policy states (a)
specifications and standards for techniques to reduce the
strength of emanations from systems and reduce the ability of
unauthorized parties to receive and make use of emanations, and
(b) rules for applying those techniques. Other nations presumably
do the same.
$ TEMPEST zone
(O) "Designated area [i.e., a physical volume] within a facility
where equipment that has appropriate TEMPEST characteristics ...
may be operated." [C4009] (See: emanation security, TEMPEST.
Compare: inspectable space.)
Tutorial: The strength of an electromagnetic signal decreases in
proportion to the square of the distance between the source and
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the receiver. Therefore, EMSEC for electromagnetic signals can be
achieved by a combination of (a) reducing the strength of
emanations to a defined level and (b) establishing around that
equipment an appropriately sized physical buffer zone from which
unauthorized entities are excluded. By making the zone large
enough, it is possible to limit the signal strength available to
entities outside the zone to a level lower than can be received
and read with known, state-of-the-art methods. Typically, the need
for and size of a TEMPEST zone established by a security policy
depends not only on the measured level of signal emitted by
equipment, but also on the perceived threat level in the
equipment's environment.
$ Terminal Access Controller (TAC) Access Control System (TACACS)
(I) A UDP-based authentication and access control protocol [R1492]
in which a network access server receives an identifier and
password from a remote terminal and passes them to a separate
authentication server for verification. (See: TACACS+, XTACACS.)
Tutorial: TACACS can provide service not only for network access
servers but also routers and other networked computing devices via
one or more centralized authentication servers. TACACS was
originally developed for ARPANET and has evolved for use in
commercial equipment.
$ TESS
(I) See: The Exponential Encryption System.
$ The Exponential Encryption System (TESS)
(I) A system of separate but cooperating cryptographic mechanisms
and functions for the secure authenticated exchange of
cryptographic keys, the generation of digital signatures, and the
distribution of public keys. TESS uses asymmetric cryptography,
based on discrete exponentiation, and a structure of self-
certified public keys. [R1824]
$ threat
1a. (I) A potential for violation of security, which exists when
there is an entity, circumstance, capability, action, or event
that could cause harm. (See: dangling threat, INFOCON level,
threat action, threat agent, threat consequence. Compare: attack,
vulnerability.)
1b. (N) Any circumstance or event with the potential to adversely
affect a system through unauthorized access, destruction,
disclosure, or modification of data, or denial of service. [C4009]
(See: sensitive information.)
Usage: (a) Frequently misused with the meaning of either "threat
action" or "vulnerability". (b) In some contexts, "threat" is used
more narrowly to refer only to intelligent threats; for example,
see definition 2 below. (c) In some contexts, "threat" is used
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more broadly to cover both definition 1 and other concepts, such
as in definition 3 below.
Tutorial: A threat is a possible danger that might exploit a
vulnerability.
- "Intentional threat": A possibility of an attack by an
intelligent entity (e.g., an individual cracker or a criminal
organization).
- "Accidental threat": A possibility of human error or omission,
unintended equipment malfunction, or natural disaster (e.g.,
fire, flood, earthquake, or windstorm). (See list in [FP031].)
The Common Criteria characterizes a threat in terms of (a) a
threat agent, (b) a presumed method of attack, (c) any
vulnerabilities that are the foundation for the attack, and (d)
the system resource that is attacked.
2. (O) The technical and operational capability of a hostile
entity to detect, exploit, or subvert a friendly system and the
demonstrated, presumed, or inferred intent of that entity to
conduct such activity.
Tutorial: To be likely to launch an attack, an adversary must have
(a) a motive to attack, (b) a method or technical capability to
make the attack, and (c) an opportunity to appropriately access
the targeted system.
3. (O) "An indication of an impending undesirable event." [Park]
Tutorial: Definition 3 was intended to include these meanings:
- "Potential threat": A possible security violation; i.e., the
same as definition 1.
- "Active threat": An expression of intent to violate security.
(Context usually distinguishes this meaning from the previous
one.)
- "Accomplished threat" or "actualized threat": That is, an
attack. Deprecated Usage: ISDs SHOULD NOT use the term "threat"
with this meaning; instead, use "threat action".
$ threat action
(I) A realization of a threat, i.e., an occurrence in which system
security is assaulted as the result of either an accidental event
or an intentional act. (See: attack, threat, threat consequence.)
Tutorial: A complete security architecture deals with both
intentional acts (i.e. attacks) and accidental events [FIPS31].
(See: (various kinds of threat actions defined as subentries
under) threat consequence.)
$ threat agent
(I) A system entity that performs a threat action, or an event
that results in a threat action.
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$ threat analysis
(I) An analysis of the probability of occurrences and consequences
of damaging actions to a system.
$ threat consequence
(I) A security violation that results from a threat action.
Tutorial: The four basic types of threat consequence are
"unauthorized disclosure", "deception", "disruption", and
"usurpation" (see definitions of these four terms for discussion
of the types of threat actions that can these consequences).
$ thumbprint
(I) A pattern of curves formed by the ridges on the tip of a
thumb. (See: biometric authentication, fingerprint.)
Deprecated Usage: ISDs SHOULD NOT use this term as a synonym for
"hash result" because that meaning mixes concepts in a potentially
misleading way.
$ ticket
(I) Synonym for "capability".
Tutorial: A ticket is usually granted by a centralized access
control server (ticket-granting agent) to authorize access to a
system resource for a limited time. Tickets can be implemented
with either symmetric cryptography (see: Kerberos) or asymmetric
cryptography (see: attribute certificate).
$ tiger team
(I) A group of evaluators employed by a system's managers to
perform penetration tests on the system.
Deprecated Term: It is likely that other cultures have different
metaphors for this concept. Therefore, to ensure international
understanding, ISDs SHOULD NOT use this term. (See: (Deprecated
Usage under) Green Book.)
$ time stamp
(I) /noun/ With respect to a data object, a label or marking in
which is recorded the time (time of day or other instant of
elapsed time) at which the label or marking was affixed to the
data object. (See: Time-Stamp Protocol.)
(O) /noun/ "With respect to a recorded network event, a data field
in which is recorded the time (time of day or other instant of
elapsed time) at which the event took place." [A1523]
Tutorial: A time stamp can be used as evidence to prove that a
data object existed (or that an event occurred) at or before a
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particular time. For example, a time stamp might be used to prove
that a digital signature based on a private key was created while
the corresponding public-key certificate was valid, i.e., before
the certificate either expired or was revoked. Establishing this
proof would enable the certificate to be used after its expiration
or revocation, to verify a signature that was created earlier.
This kind of proof is required as part of implementing PKI
services such as non-repudiation service and long-term security
services such as audit.
$ Time-Stamp Protocol
(I) An Internet protocol (RFC 3161) that specifies how a client
requests and receives a time stamp from a server for a data object
held by the client.
Tutorial: The protocol describes the format of (a) a request sent
to a time stamping authority and (b) the response that is returned
containing a time stamp. The authority creates the stamp by
concatenating (a) a hash value of the input data object with (b) a
UTC time value and other parameters (policy OID, serial number,
indication of time accuracy, nonce, DN of the authority, and
various extensions), and then signing that dataset with the
authority's private key as specified in CMS. Such an authority
typically would operate as a trusted third-party service, but
other operational models might be used.
$ timing channel
See: covert timing channel.
$ TLS
(I) See: Transport Layer Security.
$ TLSP
(N) See: Transport Layer Security Protocol.
$ TOE
(N) See: target of evaluation
$ token
1. (I) /cryptography/ See: cryptographic token. (Compare: dongle.)
2. (I) /access control/ An object that is used to control access
and is passed between cooperating entities in a protocol that
synchronizes use of a shared resource. Usually, the entity that
currently holds the token has exclusive access to the resource.
Usage: This term is heavily overloaded in the computing
literature; therefore, ISDs SHOULD NOT use this term with any
definition other than 1 or 2.
3a. (D) /authentication/ A data object or a physical device used
to verify an identity in an authentication process.
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3b. (D) /U.S. Government/ Something that the claimant in an
authentication process (i.e., the entity that claims an identity)
possesses and controls, and uses to prove the claim during the
verification step of the process. [SP63]
Usage: Deprecated usage: ISDs SHOULD NOT use this term with
definitions 3a and 3b; instead, use more specifically descriptive
and informative terms such as "authentication information" or
"cryptographic token", depending on what is meant.
NIST defines four types of claimant tokens for electronic
authentication in an information system [SP63]. ISDs SHOULD NOT
use these four NIST terms; they mix concepts in potentially
confusing ways. These terms can be avoided by using more
specifically descriptive terms as follows:
- NIST "hard token": A hardware device that contains a protected
cryptographic key. (This is a type of "cryptographic token",
and the key is a type of "authentication information".)
- NIST "one-time password device token": A personal hardware
device that generates one-time passwords. (One-time passwords
are typically generated cryptographically. Therefore, this is a
type of "cryptographic token", and the key is a type of
"authentication information".)
- NIST "soft token": A cryptographic key that typically is stored
on disk or some other magnetic media. (The key is a type of
"authentication information"; "authentication key" would be a
better description.)
- NIST "password token": A secret data value that the claimant
memorizes. (This is a "password" that is being used as
"authentication information".)
$ token backup
(I) A token management operation that stores sufficient
information in a database (e.g., in a CAW) to recreate or restore
a security token (e.g., a smart card) if it is lost or damaged.
$ token copy
(I) A token management operation that copies all the personality
information from one security token to another. However, unlike in
a token restore operation, the second token is initialized with
its own, different local security values such as PINs and storage
keys.
$ token management
(I) The process of initializing security tokens (e.g., see: smart
card), loading data into the tokens, and controlling the tokens
during their life cycle. May include performing key management and
certificate management functions; generating and installing PINs;
loading user personality data; performing card backup, card copy,
and card restore operations; and updating firmware.
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$ token restore
(I) A token management operation that loads a security token with
data for the purpose of recreating (duplicating) the contents
previously held by that or another token. (See: recovery.)
$ token storage key
(I) A cryptographic key used to protect data that is stored on a
security token.
$ top CA
(I) A synonym for "root" in a certification hierarchy.
$ top-level specification
(I) "A non-procedural description of system behavior at the most
abstract level; typically a functional specification that omits
all implementation details." [NCS04] (See: (discussion under)
security policy.)
Tutorial: A top-level specification may be descriptive or formal:
- "Descriptive top-level specification": One that is written in a
natural language like English or an informal design notation.
- "Formal top-level specification": One that is written in a
formal mathematical language to enable theorems to be proven
that show that the specification correctly implements a set of
formal requirements or a formal security model. (See:
correctness proof.)
$ traceback
(I) Identification of the source of a data packet. (See: network
weaving.)
$ tracker
(N) An attack technique for achieving unauthorized disclosure from
a statistical database. [Denns] (See: (Tutorial under) inference
control.)
$ traffic analysis
1. (I) Gaining knowledge of information by inference from
observable characteristics of data flow(s), even when the
information is encrypted or otherwise not directly available. Such
characteristics include the identities and locations of the
source(s) and destination(s), and the presence, amount, frequency,
and duration of occurrence. (See: inference, traffic-flow
confidentiality, wiretapping. Compare: signal analysis.)
2. (O) "The inference of information from observation of traffic
flows (presence, absence, amount, direction, and frequency)."
[I7498 Part 2]
$ traffic-flow analysis
(I) Synonym for "traffic analysis".
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$ traffic-flow confidentiality
1. (I) A data confidentiality service to protect against traffic
analysis. (See: communications cover.)
2. (O) "A confidentiality service to protect against traffic
analysis." [I7498 Part 2]
$ traffic padding
(I) "The generation of spurious instances of communication,
spurious data units, and/or spurious data within data units."
[I7498 Part 2]
$ tranquillity property
(N) /formal model/ Property of a system whereby the security level
of an object cannot change while the object is being processed by
the system. (See: Bell-LaPadula model.)
$ transaction
1. (I) A unit of interaction between an external entity and a
system, or between components within a system, that involves a
series of system actions or events.
2. (O) "A discrete event between user and systems that supports a
business or programmatic purpose." [M0404]
Tutorial: To maintain secure state, transactions need to be
processed coherently and reliably. Usually, they need to be
designed to be atomic, consistent, isolated, and durable [Gray]:
- "Atomic": All actions and events that comprise the transaction
are guaranteed to be completed successfully, or else the result
is as if none at all were executed.
- "Consistent": The transaction satisfies correctness constraints
defined for the data that is being processed.
- "Isolated": If two transactions are performed concurrently,
they do not interfere with each other, and it appears as though
the system performs one at a time.
- "Durable": System state and transaction semantics survive
system failures.
$ TRANSEC
(I) See: transmission security.
$ Transmission Control Code field (TCC field)
(I) A data field that provides a means to segregate traffic and
define controlled communities of interest in the security option
(option type = 130) of IP's datagram header format. The TCC values
are alphanumeric trigraphs assigned by the U.S. Government as
specified in RFC 791.
$ Transmission Control Protocol (TCP)
(I) An Internet Standard, transport-layer protocol (RFC 793) that
reliably delivers a sequence of datagrams from one computer to
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another in a computer network. (See: TCP/IP.)
Tutorial: TCP is designed to fit into a layered suite of protocols
that support internetwork applications. TCP assumes it can obtain
a simple but potentially unreliable end-to-end datagram service
(such as IP) from the lower level protocols.
$ transmission security (TRANSEC)
(I) Measures that protect communications from interception and
exploitation by means other than cryptanalysis. Usually understood
to be a part of COMSEC. (Compare: traffic flow confidentiality.)
$ Transport Layer Security (TLS)
(I) TLS Version 1.0 is an Internet protocol [R2246] that is based
on, and very similar to, SSL Version 3.0. (Compare: TLSP.)
Usage: The TLS protocol is misnamed, because it operates well
above the IPS transport layer.
$ Transport Layer Security Protocol (TLSP)
(N) An end-to-end encryption protocol (ISO 10736) that provides
security services at the bottom of OSIRM layer 4, i.e., directly
above layer 3. (Compare: TLS.)
Tutorial: TLSP evolved directly from SP4.
$ transport mode
(I) One of two ways to apply AH or ESP to protect data packets; in
this mode, the IPsec protocol encapsulates (i.e., the protection
applies to) the packets of an IPS transport protocol (e.g., TCP,
UDP), which is normally carried directly above IP in an IPS
protocol stack. (Compare: tunnel mode.)
Tutorial: An IPsec transport-mode security association is always
between two hosts; neither end has the role of a security gateway.
Whenever either end of an IPsec security association is a security
gateway, the association is required to be in tunnel mode.
$ transposition
(I) /cryptography/ A method of encryption in which elements of the
plain text retain their original form but undergo some change in
their relative position. (Compare: substitution.)
$ trap door
(I) Synonym for "back door".
$ Triple Data Encryption Algorithm
(I) An block cipher that transforms each 64-bit plaintext block by
applying the DEA three successive times, using either two or three
different keys for an effective key length of 112 or 168 bits.
[A9052, SP67]
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Example: A variation proposed for IPsec's ESP uses a 168-bit key,
consisting of three independent 56-bit values used by the DEA, and
a 64-bit initialization vector. Each datagram contains an IV to
ensure that each received datagram can be decrypted even when
other datagrams are dropped or a sequence of datagrams is
reordered in transit. [R1851]
$ triple-wrapped
(I) /S-MIME/ Data that has been signed with a digital signature,
and then encrypted, and then signed again. [R2634]
$ Trojan horse
(I) A computer program that appears to have a useful function, but
also has a hidden and potentially malicious function that evades
security mechanisms, sometimes by exploiting legitimate
authorizations of a system entity that invokes the program. (See:
malware, spyware. Compare: logic bomb, virus, worm.)
$ trust
1. (I) /information system/ The extent to which someone who relies
on a system can have confidence that the system meets its
specifications, i.e., that the system does what it claims to do
and does not perform unwanted functions. (See: trust level,
trusted system, trustworthy system. Compare: assurance.)
2. (I) /PKI/ A relationship between a certificate user and a CA in
which the user acts according to the assumption that the CA
creates only valid digital certificates.
Tutorial: "Generally, an entity is said to 'trust' a second entity
when the first entity makes the assumption that the second entity
will behave exactly as the first entity expects. This trust may
apply only for some specific function. The key role of trust in
[X.509] is to describe the relationship between an entity and a
[CA]; an entity shall be certain that it can trust the CA to
create only valid and reliable certificates." [X509]
Components can be grouped into three categories of trust [Gass]:
- "Trusted": The component is responsible for enforcing security
policy on other components; the system's security depends on
flawless operation of the component. (See: trusted process.)
- "Benign": The component is not responsible for enforcing
security policy, but it has sensitive authorizations. It must
be trusted not to intentionally violate security policy, but
security violations are assumed to be accidental and not likely
to affect overall system security.
- "Untrusted": The component is of unknown or suspicious
provenance and must be treated as deliberately malicious. (See:
malicious logic.)
$ trust anchor
(D) /PKI/ Synonym for "trusted certificate", "root", "root
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certificate", or "root key". (See: trust chain.)
Deprecated Term: ISDs SHOULD NOT use this term; it unnecessarily
duplicates the meaning of other terms and mixes concepts in a
potentially misleading way. (See: (Deprecated Term under) trust
chain.)
$ trust chain
(D) Synonym for "certification path". (See: trust anchor, trusted
certificate.)
Deprecated Term: ISDs SHOULD NOT use this term, because it
unnecessarily duplicates the meaning of the internationally
standardized term.
This term also mixes concepts in a potentially misleading way.
Having "trust" involves factors unrelated to verifying signatures
and performing other tests as specified by a standard for path
validation (e.g., RFC 3280). Thus, even if a user is able to
validate a certification path, the user still might distrust one
of the CAs that issued certificates in that path or distrust some
other aspects of the PKI.
$ trust-file PKI
(I) A non-hierarchical PKI in which each certificate user has a
local file (which is used by application software) of public-key
certificates that the user trusts as starting points (i.e., roots)
for certification paths. (Compare: hierarchical PKI, mesh PKI,
trusted certificate, web of trust.)
Example: Popular browsers are distributed with an initial file of
root certificates, which often are self-signed certificates. Users
can add certificates to the file or delete from it. The file may
be directly managed by the user, or the user's organization may
manage it from a centralized server.
$ trust hierarchy
(D) Synonym for "certification hierarchy".
Deprecated Usage: ISDs SHOULD NOT use this term because it mixes
concepts in a potentially misleading way. (See: trust, trust
chain, web of trust.)
$ trust level
(I) A characterization of a standard of security protection to be
met by an information system. (See: Common Criteria, TCSEC.)
Tutorial: A trust level is based not only on (a) the presence of
security mechanisms, but also on the use of (b) systems
engineering discipline to properly structure the system and (c)
implementation analysis to ensure that the system provides an
appropriate degree of trust.
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$ trusted certificate
(I) A certificate upon which a certificate user relies as being
valid without the need for validation testing; especially a
public-key certificate that is used to provide the first public
key in a certification path. (See: certification path, root
certificate, validation.)
Tutorial: A trusted public-key certificate might be (a) the root
certificate in a hierarchical PKI, (b) the certificate of the CA
that issued the user's own certificate in a mesh PKI, or (c) a
certificate accepted by the user in a trust-file PKI.
$ Trusted Computer System Evaluation Criteria (TCSEC)
(N) A standard for evaluating the security provided by operating
systems [CSC001, DoD1]. Known as the "Orange Book" because of the
color of its cover; first document in the Rainbow Series. (See:
Common Criteria, (Deprecated Usage under) Green Book, Orange Book,
trust level, trusted computer system. Compare: TSEC.)
Tutorial: The TCSEC defines classes of hierarchically ordered
assurance levels for rating computer systems. From highest to
lowest, the classes are as follows:
- Division A. Verified protection.
Beyond A1. Beyond current technology. (See: beyond A1.)
Class A1. Verified design. (See: SCOMP.)
- Division B: Mandatory protection.
Class B3. Security domains.
Class B2. Structured protection. (See: Multics.)
Class B1. Labeled security protection.
- Division C: Discretionary protection.
Class C2. Controlled access protection.
Class C1. Discretionary security protection.
- Division D: Minimal protection; i.e., has been evaluated but
does not meet the requirements for a higher evaluation class.
$ trusted computing base (TCB)
(N) "The totality of protection mechanisms within a computer
system, including hardware, firmware, and software, the
combination of which is responsible for enforcing a security
policy." [NCS04] (See: (discussion of "trusted" under) trust.)
$ trusted distribution
(I) /computer security/ "A trusted method for distributing the TCB
hardware, software, and firmware components, both originals and
updates, that provides methods for protecting the TCB from
modification during distribution and for detection of any changes
to the TCB that may occur." [NCS04] (See: code signing,
configuration control.)
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$ trusted key
(I) A public key upon which a user relies; especially a public key
that can be used as the first public key in a certification path.
(See: certification path, root key, validation.)
Tutorial: A trusted public key might be (a) the root key in a
hierarchical PKI, (b) the key of the CA that issued the user's own
certificate in a mesh PKI, or (c) any key accepted by the user in
a trust-file PKI.
$ trusted path
1a. (I) /COMPUSEC/ A mechanism by which a computer system user can
communicate directly and reliably with the TCB and that can only
be activated by the user or the TCB and cannot be imitated by
untrusted software within the computer. [NCS04]
1b. (I) /COMSEC/ A mechanism by which a person or process can
communicate directly with a cryptographic module and that can only
be activated by the person, process, or module, and cannot be
imitated by untrusted software within the module. [FP140]
$ trusted process
1. (I) A system component that has privileges that enable it to
affect the state of system security and that can, therefore,
through incorrect or malicious execution, violate the system's
security policy. (See: privileged process, trusted system.)
$ trusted recovery
(I) A process that, after a system has experienced a failure or an
attack, restores the system to normal operation (or to a secure
state) without causing a security compromise. (See: recovery.)
$ trusted subnetwork
(I) A subnetwork containing hosts and routers that trust each
other not to engage in active or passive attacks. (There also is
an assumption that the underlying communication channels -- e.g.,
telephone lines, or a LAN -- are protected from attack.)
$ trusted system
1. (I) /information system/ A system that operates as expected,
according to design and policy, doing what is required -- despite
environmental disruption, human user and operator errors, and
attacks by hostile parties -- and not doing other things [NRC98].
(See: trust level, trusted process. Compare: trustworthy.)
2. (N) /multilevel secure/ "A [trusted computer system is a]
system that employs sufficient hardware and software assurance
measures to allow its use for simultaneous processing of a range
of sensitive or classified information." [NCS04] (See: multilevel
security mode.)
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$ Trusted Systems Interoperability Group (TSIG)
(N) A forum of computer vendors, system integrators, and users
devoted to promoting interoperability of trusted computer systems.
$ trustworthy system
1. (I) A system that not only is trusted, but also for which the
trust can be guaranteed in some convincing way, such as through
formal analysis or code review. (See: trust. Compare: trusted.)
2. (O) /Digital Signature Guidelines/ "Computer hardware,
software, and procedures that: (a) are reasonably secure from
intrusion and misuse; (b) provide a reasonably reliable level of
availability, reliability, and correct operation; (c) are
reasonably suited to performing their intended functions; and (d)
adhere to generally accepted security principles." [ABA]
$ TSEC
(O) See: Telecommunications Security Nomenclature System.
(Compare: TCSEC.)
$ TSIG
(N) See: Trusted System Interoperability Group.
$ tunnel
1. (I) A communication channel created in a computer network by
encapsulating (i.e., layering) a communication protocol's data
packets in (i.e., above) a second protocol that normally would be
carried above, or at the same layer as, the first one. (See: L2TP,
VPN.)
Tutorial: Tunneling can involve almost any OSIRM or TCP/IP
protocol layers; for example, a TCP connection between two hosts
could conceivably be tunneled through email messages across the
Internet. However, a tunnel usually is a logical point-to-point
link -- i.e., an OSIRM layer 2 connection -- created by
encapsulating the layer 2 protocol in an IPS transport layer
protocol (such as TCP), in an IPS network or internetwork layer
protocol (such as IP), or in another layer 2 protocol. In many
cases, the encapsulation is accomplished with an extra,
intermediate protocol, i.e., a tunneling protocol (such as L2TP)
that is layered between the tunneled layer 2 protocol and the
encapsulating protocol.
Tunneling can be used to move data between computers that use a
protocol not supported by the network connecting them. Tunneling
also can enable a computer network to use the services of a second
network as though the second network were a set of point-to-point
links between the first network's nodes. (See: virtual private
network.)
2. (O) /SET/ The name of a SET private extension that indicates
whether the CA or the payment gateway supports passing encrypted
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messages to the cardholder through the merchant. If so, the
extension lists OIDs of symmetric encryption algorithms that are
supported.
$ tunnel mode
(I) One of two ways to apply the IPsec protocols (AH and ESP) to
protect data packets; in this mode, the IPsec protocol
encapsulates (i.e., the protection applies to) IP packets, rather
than the packets of higher layer protocols. (Compare: transport
mode.)
Tutorial: Each end of a tunnel-mode security association may be
either a host or a security gateway. Whenever either end of an
IPsec security association is a security gateway, the association
is required to be in tunnel mode.
$ two-person control
(I) The close surveillance and control of a system, a process, or
materials (especially with regard to cryptography) at all times by
a minimum of two appropriately authorized persons, each capable of
detecting incorrect and unauthorized procedures with respect to
the tasks to be performed and each familiar with established
security requirements. (See: dual control, no-lone zone.)
$ type 0 product
(O) /cryptography, U.S. Government/ Classified cryptographic
equipment endorsed by NSA specifically for use (when appropriately
keyed) in electronically distributing bulk keying material.
$ type 1 product
(O) /cryptography, U.S. Government/ "Classified or controlled
cryptographic item endorsed by the NSA for securing classified and
sensitive U.S. Government information, when appropriately keyed.
The term refers only to products, and not to information, key,
services, or controls. Type 1 products contain classified NSA
algorithms. They are available to U.S. Government users, their
contractors, and federally sponsored non-U.S. Government
activities subject to export restrictions in accordance with
International Traffic in Arms Regulation." [C4009] (See: ITAR.)
$ type 2 product
(O) /cryptography, U.S. Government/ "Unclassified cryptographic
equipment, assembly, or component, endorsed by the NSA, for use in
national security systems as defined in Title 40 U.S.C. Section
1452." [C4009] (See: national security system. Compare: EUCI.)
$ type 3 algorithm
(O) /cryptography, U.S. Government/ "Cryptographic algorithm
registered by [NIST] and published as a [FIPS] for use in
protecting unclassified sensitive information or commercial
information." [C4009]
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$ type 4 algorithm
(O) /cryptography, U.S. Government/ "Unclassified cryptographic
algorithm that has been registered by [NIST] but not published as
a [FIPS]." [C4009]
$ UDP
(I) See: User Datagram Protocol.
$ UDP flood
(I) A denial-of-service attack that connects one system's UDP test
function that generates a series of characters for each packet it
receives, to another system's UPD test function that echoes any
character it receives, resulting in a nonstop flood of data
between the two systems.
$ unauthorized disclosure
(I) A circumstance or event whereby an entity gains access to
information for which the entity is not authorized.
Tutorial: This type of threat consequence can be caused by the
following types of threat actions: exposure, interception,
inference, intrusion. Some methods of protecting against this
consequence include access control, flow control, and inference
control. (See: data confidentiality.)
$ unauthorized user
(I) /access control/ A system entity that accesses a system
resource for which the entity has not received an authorization.
(See: user. Compare: authorized user, insider, outsider.)
Usage: The term is used in many ways and could easily be
misunderstood; therefore, ISDs that use this term SHOULD state a
definition for it.
$ uncertainty
(I) An information-theoretic measure (usually stated as a number
of bits) of the minimum amount of plaintext information that needs
to be recovered from cipher text in order to learn the entire
plain text that was encrypted. [SP63] (See: entropy.)
$ unclassified
(I) Not classified.
$ unencrypted
(I) Not encrypted.
$ unforgeable
(I) /cryptography/ The property of a cryptographic data structure
(i.e., a data structure that is defined using one or more
cryptographic functions; e.g., see digital certificate) that makes
it computationally infeasible to construct (i.e., compute) an
unauthorized but correct value of the structure without having
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knowledge of one of more keys.
Tutorial: This definition is narrower than general English usage,
where "unforgeable" means unable to be fraudulently created or
duplicated. In that broader sense, anyone can forge a digital
certificate containing any set of data items whatsoever by
generating the to-be-signed certificate and signing it with any
private key whatsoever. But for PKI purposes, the forged data
structure is invalid if it is not signed with the true private key
of the claimed issuer; thus, the forgery will be detected when a
certificate user uses the true public key of the claimed issuer to
verify the signature.
$ uniform resource identifier (URI)
(I) A type of formatted identifier (RFC 1630) that encapsulates
the name of an Internet object, and labels it with an
identification of the name space, thus producing a member of the
universal set of names in registered name spaces and of addresses
referring to registered protocols or name spaces.
Tutorial: URIs are used in HTML to identify the target of
hyperlinks. In common practice, URIs include URLs and relative
URLs (RFC 1808).
$ uniform resource locator (URL)
(I) A type of formatted identifier (RFC 1738) that describes the
access method and location of an information resource object on
the Internet.
Tutorial: A URL is a URI that provides explicit instructions on
how to access the named object. For example,
"ftp://bbnarchive.bbn.com/foo/bar/picture/cambridge.zip" is a URL.
The part before the colon specifies the access scheme or protocol,
and the part after the colon is interpreted according to that
access method. Usually, two slashes after the colon indicate the
host name of a server (written as a domain name). In an FTP or
HTTP URL, the host name is followed by the path name of a file on
the server. The last (optional) part of a URL may be either a
fragment identifier that indicates a position in the file, or a
query string.
$ uniform resource name (URN)
(I) A URI that has an institutional commitment to persistence and
availability.
$ untrusted process
1. (I) A system component that is not able to affect the state of
system security through incorrect or malicious operation. Example:
A component that has its operations confined by a security kernel.
(See: trusted process.)
2. (I) A system component that (a) has not been evaluated or
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examined for adherence to a specified security policy and,
therefore, (b) must be assumed to contain logic that might attempt
to circumvent system security.
$ UORA
(O) See: user-PIN ORA.
$ update
See: certificate update and key update.
$ upgrade
(I) /data security/ Increase the classification level of data
without changing the information content of the data. (Compare:
downgrade. See: regrade.)
$ URI
(I) See: uniform resource identifier.
$ URL
(I) See: uniform resource locator.
$ URN
(I) See: uniform resource name.
$ user
(I) An active system entity that uses a product or service
provided by the system, or that accesses system resources to
produce a product or service of the system. (See: access, [R2504].
Compare: authorized user, manager, operator, principal, subject,
subscriber, unauthorized user.)
Usage: The term is used in many ways and could easily be
misunderstood; therefore, ISDs that use this term SHOULD state a
definition for it.
- This term usually refers to an entity that has been authorized
to access the system, but the term sometimes is used without
regard for whether access is authorized.
- This term usually refers to a living human being acting either
personally or in an organizational role, but the term may refer
to an automated process in the form of either hardware or
software or both, or to a set of persons, or to a set of
processes
- ISDs SHOULD exclude the case of a mixed set containing both
persons and processes. The exclusion is intended to prevent
situations that might require a security policy to be
interpreted in two different and conflicting ways.
$ user authentication service
(I) A security service that verifies that the identity claimed by
an entity that attempts to access the system. (See:
authentication, user.)
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$ User Datagram Protocol (UDP)
(I) An Internet Standard, transport-layer protocol (RFC 768) that
delivers a sequence of datagrams from one computer to another in a
computer network. (See: UPD flood.)
Tutorial: UDP assumes that IP is the underlying protocol. UDP
enables application programs to send transaction-oriented data to
other programs with minimal protocol mechanism. UDP does not
provide reliable delivery, flow control, sequencing, or other end-
to-end service guarantees that TCP does.
$ user identity
(I) See: identity.
$ user identifier
(I) See: identifier.
$ user PIN
(O) /MISSI/ One of two PINs that control access to the functions
and stored data of a FORTEZZA PC card. Knowledge of the user PIN
enables the card user to perform the FORTEZZA functions that are
intended for use by an end user. (Compare: SSO PIN.)
$ user-PIN ORA (UORA)
(O) /MISSI/ A MISSI organizational RA that operates in a mode in
which the ORA performs only the subset of card management
functions that are possible with knowledge of the user PIN for a
FORTEZZA PC card. (See: no-PIN ORA, SSO-PIN ORA.)
$ usurpation
(I) A circumstance or event that results in control of system
services or functions by an unauthorized entity. This type of
threat consequence can be caused by the following types of threat
actions: misappropriation, misuse. (See: access control.)
$ UTCTime
(N) The ASN.1 data type "UTCTime" contains a calendar date
(YYMMDD) and a time to a precision of either one minute (HHMM) or
one second (HHMMSS), where the time is either (a) Coordinated
Universal Time or (b) the local time followed by an offset that
enables Coordinated Universal Time to be calculated. Note: UTCTime
has the Year 2000 problem. (See: Coordinated Universal Time,
GeneralizedTime.)
$ v1 certificate
(I) An abbreviation that ambiguously refers to either an "X.509
public-key certificate in version 1 format" or an "X.509 attribute
certificate in version 1 format".
Deprecated Usage: ISDs MAY use this term as an abbreviation for
"version 1 X.509 public-key certificate", but only after using the
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full term at the first instance. Otherwise, the term is ambiguous,
because X.509 specifies both v1 public-key certificates and v1
attribute certificates. (See: X.509 attribute certificate, X.509
public-key certificate.)
$ v1 CRL
(I) An abbreviation for "X.509 CRL in version 1 format".
Usage: ISDs MAY use this abbreviation, but SHOULD use the full
term at its first occurrence and define the abbreviation there.
$ v2 certificate
(I) An abbreviation for "X.509 public-key certificate in version 2
format".
Usage: ISDs MAY use this abbreviation, but SHOULD use the full
term at its first occurrence and define the abbreviation there.
$ v2 CRL
(I) An abbreviation for "X.509 CRL in version 2 format".
Usage: ISDs MAY use this abbreviation, but SHOULD use the full
term at its first occurrence and define the abbreviation there.
$ v3 certificate
(I) An abbreviation for "X.509 public-key certificate in version 3
format".
Usage: ISDs MAY use this abbreviation, but SHOULD use the full
term at its first occurrence and define the abbreviation there.
$ valid certificate
1. (I) A digital certificate that can be validated successfully.
(See: validate, verify.)
2. (I) A digital certificate for which the binding of the data
items can be trusted.
$ valid signature
(D) Synonym for "authentic signature".
Deprecated Term: ISDs SHOULD NOT use this term; instead, say
"authentic signature". This Glossary recommends saying "validate
the certificate" and "verify the signature"; therefore, it would
be inconsistent to say that a signature is "valid". (See:
validate, verify.)
$ validate
1. (I) Establish the soundness or correctness of a construct.
Example: certificate validation. (See: validate vs. verify.)
2. (I) To officially approve something, sometimes in relation to a
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standard. Example: NIST validates cryptographic modules for
conformance with FIPS PUB 140 [FP140].
$ validate vs. verify
Usage: To ensure consistency and align with ordinary English
usage, ISDs SHOULD comply with the following two rules:
- Rule 1: Use "validate" when referring to a process intended to
establish the soundness or correctness of a construct (e.g.,
see: certificate validation). (See: validate.)
- Rule 2: Use "verify" when referring to a process intended to
test or prove the truth or accuracy of a fact or value (e.g.,
see: authenticate). (See: verify.)
Tutorial: The Internet security community sometimes uses these two
terms inconsistently, especially in a PKI context. Most often,
however, we say "verify the signature" but say "validate the
certificate". That is, we "verify" atomic truths but "validate"
data structures, relationships, and systems that are composed of
or depend on verified items. This usage has a basis in Latin:
The word "valid" derives from a Latin word that means "strong".
Thus, to validate means to check that a construct is sound. For
example, a certificate user validates a public-key certificate to
establish trust in the binding that the certificate asserts
between an identity and a key. This can include checking various
aspects of the certificate's construction, such as verifying the
digital signature on the certificate by performing calculations,
verifying that the current time is within the certificate's
validity period, and validating a certification path involving
additional certificates.
The word "verify" derives from a Latin word that means "true".
Thus, to verify means to check the truth of an assertion by
examining evidence or performing tests. For example, to verify an
identity, an authentication process examines identification
information that is presented or generated. To validate a
certificate, a certificate user verifies the digital signature on
the certificate by performing calculations, verifies that the
current time is within the certificate's validity period, and may
need to validate a certification path involving additional
certificates.
$ validation
(I) See: validate vs. verify.
$ validity period
(I) A data item in a digital certificate that specifies the time
period for which the binding between data items (especially
between the subject name and the public key value in a public-key
certificate) is valid, except if the certificate appears on a CRL
or the key appears on a CKL.
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$ value-added network (VAN)
(I) A computer network or subnetwork (usually a commercial
enterprise) that transmits, receives, and stores EDI transactions
on behalf of its users.
Tutorial: A VAN may also provide additional services, ranging from
EDI format translation, to EDI-to-FAX conversion, to integrated
business systems.
$ VAN
(I) See: value-added network.
$ verification
1. (I) /authentication/ Presenting information to establish the
truth of a claimed identity. (See: validate vs. verify.)
2. (N) /computer security/ The process of comparing two levels of
system specification for proper correspondence, such as comparing
a security model with a top-level specification, a top-level
specification with source code, or source code with object code.
[NCS04]
$ verified design
(O) See: TCSEC Class A1.
$ verify
(I) To test or prove the truth or accuracy of a fact or value. For
example, see "authenticate". (See: validate vs. verify.)
$ vet
(I) /verb/ To examine or evaluate thoroughly. (Compare:
authenticate, identity proofing, validate, verify.)
$ violation
See: security violation.
$ virtual private network (VPN)
(I) A restricted-use, logical (i.e., artificial or simulated)
computer network that is constructed from the system resources of
a relatively public, physical (i.e., real) network (e.g., the
Internet), often by using encryption (located at hosts or
gateways), and often by tunneling links of the virtual network
across the real network.
Tutorial: A VPN is generally less expensive to build and operate
than a dedicated real network, because the virtual network shares
the cost of system resources with other users of the underlying
real network. For example, if a corporation has LANs at several
different sites, each connected to the Internet by a firewall, the
corporation could create a VPN by (a) using encrypted tunnels to
connect from firewall to firewall across the Internet and (b) not
allowing any other traffic through the firewalls.
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$ virus
(I) A self-replicating (and usually hidden) section of computer
software (usually malicious logic) that propagates by infecting --
i.e., inserting a copy of itself into and becoming part of --
another program. A virus cannot run by itself; it requires that
its host program be run to make the virus active.
$ VisaCash
(O) A smartcard-based electronic money system that incorporates
cryptography and can be used to make payments via the Internet.
(See: IOTP.)
$ volatile media
(I) Storage media that require an external power supply to
maintain stored information. (Compare: non-volatile media,
permanent storage.)
$ VPN
(I) See: virtual private network.
$ vulnerability
(I) A flaw or weakness in a system's design, implementation, or
operation and management that could be exploited to violate the
system's security policy. (See: harden.)
Tutorial: A system can have three types of vulnerabilities: (a)
vulnerabilities in design or specification; (b) vulnerabilities in
implementation; and (c) vulnerabilities in operation and
management. Most systems have one or more vulnerabilities, but
this does not mean that the systems are too flawed to use. Not
every threat results in an attack, and not every attack succeeds.
Success depends on the degree of vulnerability, the strength of
attacks, and the effectiveness of any countermeasures in use. If
the attacks needed to exploit a vulnerability are very difficult
to carry out, then the vulnerability may be tolerable. If the
perceived benefit to an attacker is small, then even an easily
exploited vulnerability may be tolerable. However, if the attacks
are well understood and easily made, and if the vulnerable system
is employed by a wide range of users, then it is likely that there
will be enough motivation for someone to launch an attack.
$ W3
(D) Synonym for WWW.
Deprecated Abbreviation: This abbreviation could be confused with
W3C; use "WWW" instead.
$ W3C
See: World Wide Web Consortium.
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$ war dialer
(I) A computer program that automatically dials a series of
telephone numbers to find lines connected to computer systems, and
catalogs those numbers so that a cracker can try to break the
systems.
Deprecated Usage: This term could confuse international readers;
therefore, ISDs that use it SHOULD state a definition for it.
$ Wassenaar Arrangement
(N) The Wassenaar Arrangement on Export Controls for Conventional
Arms and Dual-Use Goods and Technologies is a global, multilateral
agreement approved by 33 countries in July 1996 to contribute to
regional and international security and stability, by promoting
information exchange concerning, and greater responsibility in,
transfers of arms and dual-use items, thus preventing
destabilizing accumulations. (See: International Traffic in Arms
Regulations.)
Tutorial: The Arrangement began operations in September 1996 with
headquarters in Vienna. The participating countries were
Argentina, Australia, Austria, Belgium, Bulgaria, Canada, Czech
Republic, Denmark, Finland, France, Germany, Greece, Hungary,
Ireland, Italy, Japan, Luxembourg, Netherlands, New Zealand,
Norway, Poland, Portugal, Republic of Korea, Romania, Russian
Federation, Slovak Republic, Spain, Sweden, Switzerland, Turkey,
Ukraine, United Kingdom, and United States.
Participating countries seek through their national policies to
ensure that transfers do not contribute to the development or
enhancement of military capabilities that undermine the goals of
the arrangement, and are not diverted to support such
capabilities. The countries maintain effective export controls for
items on the agreed lists, which are reviewed periodically to
account for technological developments and experience gained.
Through transparency and exchange of views and information,
suppliers of arms and dual-use items can develop common
understandings of the risks associated with their transfer and
assess the scope for coordinating national control policies to
combat these risks. Members provide semi-annual notification of
arms transfers, covering seven categories derived from the UN
Register of Conventional Arms. Members also report transfers or
denials of transfers of certain controlled dual-use items.
However, the decision to transfer or deny transfer of any item is
the sole responsibility of each participating country. All
measures undertaken with respect to the arrangement are in
accordance with national legislation and policies and are
implemented on the basis of national discretion.
$ watermarking
See: digital watermarking.
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$ weak key
(I) In the context of a particular cryptographic algorithm, a key
value that provides poor security.
Example: The DEA has four "weak keys" [Schn] for which encryption
produces the same result as decryption. It also has ten pairs of
"semi-weak keys" [Schn] (also known as "dual keys" [FP074]) for
which encryption with one key in the pair produces the same result
as decryption with the other key.
$ web, Web
1. (C) /not capitalized/ ISD SHOULD NOT capitalize "web" when
using the term (usually as an adjective) to refer generically to
technology -- such as web browsers, web servers, HTTP, and HTML --
that is used in the Web or similar networks.
2. (I) /capitalized/ ISDs SHOULD capitalize "Web" when using the
term (as either a noun or an adjective) to refer specifically to
the World Wide Web. (Similarly, see: internet.)
Usage: IETF documents SHOULD spell out "World Wide Web" fully at
the first instance of usage and MUST use "Web" and "web"
especially carefully where confusion with the PGP web of trust is
possible.
$ web of trust
(D) /PGP/ A trust-file PKI technique used for building a file of
trusted public keys by making personal judgments about being able
to trust certain people to be holding properly certified keys of
other people. (See: certification hierarchy, mesh PKI.)
Deprecated Term: ISDs SHOULD NOT use this term; it mixes concepts
in a potentially misleading way. This PKI technique does not
depend on World Wide Web technology.
$ web server
(I) A software process that runs on a host computer connected to a
network and responds to HTTP requests made by client web browsers.
$ WEP
(N) See: Wired Equivalency Protocol.
$ Wired Equivalent Privacy (WEP)
(N) A cryptographic protocol defined in the IEEE 802.11 standard
encapsulate the packets on wireless LANs. (Frequently referred to
as "Wired Equivalency Protocol".)
Tutorial: The WEP design, which uses RC4 to encrypt the plaintext
and a CRC, has been shown to be flawed in multiple ways; and it
also has often been flawed in implementation and management.
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$ wiretapping
(I) An attack that intercepts and accesses information contained
in a data flow in a communication system. (See: active
wiretapping, end-to-end encryption, passive wiretapping.)
Usage: Although the term originally referred to making a
mechanical connection to an electrical conductor that links two
nodes, it is now used to refer to accessing information from any
sort of medium used for a link or even from a node, such as a
gateway or subnetwork switch.
Tutorial: Wiretapping can be characterized according to intent:
- "Active wiretapping" attempts to alter the data or otherwise
affect the flow.
- "Passive wiretapping" only attempts to observe the data flow
and gain knowledge of information contained in it.
$ work factor
1. (I) /COMPUSEC/ The estimated amount of effort or time that can
be expected to be expended by a potential intruder to penetrate a
system, or defeat a particular countermeasure, when using
specified amounts of expertise and resources. (See: strength.)
2. (I) /cryptography/ The estimated amount of computing power and
time needed to break a cryptographic system.
$ World Wide Web ("the Web", WWW)
(N) The global, hypermedia-based collection of information and
services that is available on Internet servers and is accessed by
browsers using Hypertext Transfer Protocol and other information
retrieval mechanisms. (See: web vs. Web, [R2084].)
$ World Wide Web Consortium (W3C)
(N) Created in October 1994 to develop and standardize protocols
to promote the evolution and interoperability of the Web, and now
consisting of over 300 member organizations (commercial firms,
government agencies, schools, and other organizations).
Tutorial: W3C Recommendations are developed through a process
similar to that of the standards published by other organizations,
such as the IETF. The W3 Recommendation Track (i.e., standards
track) has four levels of increasing maturity: Working, Candidate
Recommendation, Proposed Recommendation, and W3C Recommendation
W3C Recommendations are similar to the standards published by
other organizations. (Compare: Internet Standard, ISO.)
$ worm
(I) A computer program that can run independently, can propagate a
complete working version of itself onto other hosts on a network,
and may consume system resources destructively. (See: Morris Worm,
virus.)
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$ wrap
(D) To use cryptography to provide data confidentiality service
for keying material. (See: encrypt. Compare: seal.)
Deprecated Term: ISDs SHOULD NOT use this term as defined here;
the definition duplicates the meaning of other, standard terms.
Instead, use "encrypt" or another term that is specific with
regard to the mechanism being used.
$ write
(I) /COMPUSEC/ A fundamental operation in an information system
that results in a flow of information only from a subject to an
object. (See: access mode.)
$ WWW
(I) See: World Wide Web.
$ X.400
(N) An ITU-T Recommendation [X400] that is one part of a joint
ITU-T/ISO multi-part standard (X.400-X.421) that defines the
Message Handling Systems. (The ISO equivalent is IS 10021, parts
1-7.) (See: Message Handling Systems.)
$ X.500
(N) An ITU-T Recommendation [X500] that is one part of a joint
ITU-T/ISO multi-part standard (X.500-X.525) that defines the X.500
Directory, a conceptual collection of systems that provide
distributed directory capabilities for OSI entities, processes,
applications, and services. (The ISO equivalent is IS 9594-1 and
related standards, IS 9594-x.) (See: directory vs. Directory,
X.509.)
Tutorial: The X.500 Directory is structured as a tree (the
Directory Information Tree), and information is stored in
directory entries. Each entry is a collection of information about
one object, and each object has a DN. A directory entry is
composed of attributes, each with a type and one or more values.
For example, if a PKI uses the Directory to distribute
certificates, then the X.509 public-key certificate of an end user
is normally stored as a value of an attribute of type
"userCertificate" in the Directory entry that has the DN that is
the subject of the certificate.
$ X.509
(N) An ITU-T Recommendation [X509] that defines a framework to
provide and support data origin authentication and peer entity
authentication, including formats for X.509 public-key
certificates, X.509 attribute certificates, and X.509 CRLs. (The
ISO equivalent is IS 9498-4.) (See: X.500.)
Tutorial: X.509 describes two "levels" of authentication: "simple
authentication" and "strong authentication". It recommends, "While
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simple authentication offers some limited protection against
unauthorized access, only strong authentication should be used as
the basis for providing secure services."
$ X.509 attribute certificate
(N) An attribute certificate in the version 1 (v1) format defined
by X.509. (The v1 designation for an X.509 attribute certificate
is disjoint from the v1 designation for an X.509 public-key
certificate, and from the v1 designation for an X.509 CRL.)
Tutorial: An X.509 attribute certificate has a "subject" field,
but the attribute certificate is a separate data structure from
that subject's public-key certificate. A subject may have multiple
attribute certificates associated with each of its public-key
certificates, and an attribute certificate may be issued by a
different CA than the one that issued the associated public-key
certificate.
An X.509 attribute certificate contains a sequence of data items
and has a digital signature that is computed from that sequence.
In addition to the signature, an attribute certificate contains
items 1 through 9 listed below:
1. version Identifies v1.
2. subject Is one of the following:
2a. baseCertificateID Issuer and serial number of an
X.509 public-key certificate.
2b. subjectName DN of the subject.
3. issuer DN of the issuer (the CA who signed).
4. signature OID of algorithm that signed the cert.
5. serialNumber Certificate serial number;
an integer assigned by the issuer.
6. attCertValidityPeriod Validity period; a pair of UTCTime
values: "not before" and "not after".
7. attributes Sequence of attributes describing the
subject.
8. issuerUniqueId Optional, when a DN is not sufficient.
9. extensions Optional.
$ X.509 authority revocation list
(N) An ARL in one of the formats defined by X.509 -- version 1
(v1) or version 2 (v2). A specialized kind of certificate
revocation list.
$ X.509 certificate
(N) Synonym for "X.509 public-key certificate".
Usage: ISDs MAY use this term as an abbreviation for "X.509
public-key certificate", but only after using the full term at the
first instance. Otherwise, the term is ambiguous, because X.509
specifies both public-key certificates and attribute certificates.
(See: X.509 attribute certificate, X.509 public-key certificate.)
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Deprecated Usage: ISDs SHOULD NOT use this term as an abbreviation
for "X.509 attribute certificate", because the term is likely to
be misunderstood to mean "X.509 public-key certificate".
$ X.509 certificate revocation list (CRL)
(N) A CRL in one of the formats defined by X.509 -- version 1 (v1)
or version 2 (v2). (The v1 and v2 designations for an X.509 CRL
are disjoint from the v1 and v2 designations for an X.509 public-
key certificate, and from the v1 designation for an X.509
attribute certificate.) (See: certificate revocation.)
Usage: ISDs SHOULD NOT refer to an X.509 CRL as a digital
certificate; however, note that an X.509 CRL does meet this
Glossary's definition of "digital certificate". Like a digital
certificate, an X.509 CRL makes an assertion and is signed by a
CA. But instead of binding a key or other attributes to a subject,
an X.509 CRL asserts that certain previously-issued X.509
certificates have been revoked.
Tutorial: An X.509 CRL contains a sequence of data items and has a
digital signature computed on that sequence. In addition to the
signature, both v1 and v2 contain items 2 through 6b listed below.
Version 2 contains item 1 and may optionally contain 6c and 7.
1. version Optional. If present, identifies v2.
2. signature OID of the algorithm that signed CRL.
3. issuer DN of the issuer (the CA who signed).
4. thisUpdate A UTCTime value.
5. nextUpdate A UTCTime value.
6. revokedCertificates 3-tuples of 6a, 6b, and (optional) 6c:
6a. userCertificate A certificate's serial number.
6b. revocationDate UTCTime value for the revocation date.
6c. crlEntryExtensions Optional.
7. crlExtensions Optional.
$ X.509 public-key certificate
(N) A public-key certificate in one of the formats defined by
X.509 -- version 1 (v1), version 2 (v2), or version 3 (v3). (The
v1 and v2 designations for an X.509 public-key certificate are
disjoint from the v1 and v2 designations for an X.509 CRL, and
from the v1 designation for an X.509 attribute certificate.)
Tutorial: An X.509 public-key certificate contains a sequence of
data items and has a digital signature computed on that sequence.
In addition to the signature, all three versions contain items 1
through 7 listed below. Only v2 and v3 certificates may also
contain items 8 and 9, and only v3 may contain item 10.
1. version Identifies v1, v2, or v3.
2. serialNumber Certificate serial number;
an integer assigned by the issuer.
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3. signature OID of algorithm that was used to
sign the certificate.
4. issuer DN of the issuer (the CA who signed).
5. validity Validity period; a pair of UTCTime
values: "not before" and "not after".
6. subject DN of entity who owns the public key.
7. subjectPublicKeyInfo Public key value and algorithm OID.
8. issuerUniqueIdentifier Defined for v2, v3; optional.
9. subjectUniqueIdentifier Defined for v2, v2; optional.
10. extensions Defined only for v3; optional.
$ X9
See: (Accredited Standards Committee X9 under) ANSI.
$ XML
(N) See: Extensible Markup Language.
$ XML-Signature.
(N) A W3C Recommendation (i.e. approved standard) that specifies
XML syntax and processing rules for creating and representing
digital signatures (based on asymmetric cryptography) that can be
applied to any digital content (i.e., any data object) including
other XML material.
$ XTACACS
(I) Cisco Corporation's implementation of the Terminal Access
Controller (TAC) Access Control System. This implementation
enhances and extends the original TACACS. (See: TACACS, TACACS+.)
$ Yellow Book
(D) Synonym for "Computer Security Requirements: Guidance for
Applying the [U.S.] Department of Defense Trusted Computer System
Evaluation Criteria in Specific Environments" [CSC3] (See: (first
law under) Courtney's laws).
Deprecated Term: ISDs SHOULD NOT use this term as a synonym for
that or any other document. Instead, use the full proper name of
the document or, in subsequent references, a conventional
abbreviation. (See: (Deprecated Usage under) Green Book, Rainbow
Series.)
$ zero-knowledge proof
(I) /cryptography/ A proof-of-possession protocol whereby a system
entity can prove possession of some information to another entity,
without revealing any of that information. (See: proof-of-
possession protocol.)
$ zeroize
1. (I) Synonym for "purge". Usage: Particularly with regard to
erasing keys that are stored in a cryptographic module.
2. (O) Erase electronically stored data by altering the contents
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of the data storage so as to prevent the recovery of the data.
[FP140]
$ zombie
(I) An Internet host computer that has been surreptitiously
penetrated by an intruder that installed malicious daemon software
to cause the host to operate as an accomplice in attacking other
hosts, particularly in distributed attacks that attempt denial of
service through flooding.
Deprecated Term: It is likely that other cultures have different
metaphors for this concept. Therefore, to ensure international
understanding, ISDs SHOULD NOT use this term. (See: (Deprecated
Usage under) Green Book.)
$ zone of control
(O) /EMSEC/ Synonym for "inspectable space". [C4009] (See:
TEMPEST.)
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5. References
This Glossary focuses on the Internet Standards Process. Therefore,
this set of references emphasizes international, governmental, and
industry standards documents.
[A1523] American National Standards Institute, "American National
Standard Telecomm Glossary", ANSI T1.523-2001.
[A3092] ---, "American National Standard Data Encryption Algorithm",
ANSI X3.92-1981, 30 Dec 1980.
[A9009] ---, "Financial Institution Message Authentication
(Wholesale)", ANSI X9.9-1986, 15 Aug 1986.
[A9017] ---, "Financial Institution Key Management (Wholesale)",
X9.17, 4 Apr 1985. [Defines procedures for the manual and
automated management of keying material and uses DES to
provide key management for a variety of operational
environments.]
[A9042] ---, "Public key Cryptography for the Financial Service
Industry: Agreement of Symmetric Keys Using Diffie-Hellman
and MQV Algorithms", X9.42, 29 Jan 1999.
[A9052] ---, "Triple Data Encryption Algorithm Modes of Operation",
X9.52-1998, ANSI approval 9 Nov 1998.
[A9062] ---, "Public Key Cryptography for the Financial Services
Industry: The Elliptic Curve Digital Signature Algorithm
(ECDSA)", X9.62-1998, ANSI approval 7 Jan 1999.
[A9063] ---, "---: Key Agreement and Key Transport Using Elliptic
Curve Cryptography", X9.63-2001.
[ABA] American Bar Association, "Digital Signature Guidelines:
Legal Infrastructure for Certification Authorities and
Secure Electronic Commerce", Chicago, IL, 1 Aug 1996.
[ACM] Association for Computing Machinery, "Communications of the
ACM", Jul 1998 issue with: M. Yeung, "Digital Watermarking";
N. Memom and P. Wong, "Protecting Digital Media Content";
and S. Craver, B.-L. Yeo, and M. Yeung, "Technical Trials
and Legal Tribulations".
[Ande] J. Anderson, "Computer Security Technology Planning Study",
ESD-TR-73-51, Vols. I and II, USAF Electronics Systems Div.,
Bedford, MA, Oct 1972. (Available as AD-758206 and -772806,
National Technical Information Service, Springfield, VA.)
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[ANSI] American National Standards Institute, "Role Based Access
Control", Secretariat, Information Technology Industry
Council, BSR INCITS 359, DRAFT, 10 Nov 2003.
[Army] U.S. Army Corps of Engineers, "Electromagnetic Pulse (EMP)
and Tempest Protection for Facilities", EP 1110-3-2, 31 Dec
1990.
[B1822] Bolt Baranek and Newman Inc., "Appendix H: Interfacing a
Host to a Private Line Interface" in "Specifications for the
Interconnection of a Host and an IMP", BBN Report No. 1822,
revised, Dec 1983.
[B4799] ---, "A History of the Arpanet: The First Decade", BBN
Report No. 4799, Apr 1981.
[BS7799] British Standards Institution, "Information Security
Management, Part 1: Code of Practice for Information
Security Management", BS 7799-1:1999, effective 15 May 1999.
---, ---, "Part 2: Specification for Information Security
Management Systems", BS 7799-2:1999, effective 15 May 1999.
[Bell] D. Bell and L. LaPadula, "Secure Computer Systems:
Mathematical Foundations and Model", M74-244, The MITRE
Corporation, Bedford, MA, May 1973. (Available as AD-771543,
National Technical Information Service, Springfield, VA.)
[Biba] K. Biba, "Integrity Considerations for Secure Computer
Systems", ESD-TR-76-372, USAF Electronic Systems Division,
Bedford, MA, Apr 1977.
[BN89] D. Brewer and M. Nash, "The Chinese wall security policy",
in "Proceedings of IEEE Symposium on Security and Privacy",
May 1989, pp. 205-214.
[C4009] Committee National Security System, "National Information
Assurance (IA) Glossary", CNSS Instruction No. 4009, revised
May 2003.
[CCIB] Common Criteria Implementation Board, "Common Criteria for
Information Technology Security Evaluation, Part 1:
Introduction and General Model", ver. 2.0, CCIB-98-026, May
1998.
[Chau] D. Chaum, "Untraceable Electronic Mail, Return Addresses,
and Digital Pseudonyms", in "Communications of the ACM",
vol. 24, no. 2, Feb 1981, pp. 84-88.
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[Cheh] M. Cheheyl, M. Gasser, G. Huff, and J. Millen, "Verifying
Security", in "ACM Computing Surveys", vol. 13, no. 3, Sep
1981, pp. 279-339.
[Chris] M. Chrissis et al, 1993. "SW-CMM [Capability Maturity Model
for Software Version", Release 3.0, Software Engineering
Institute, Carnegie Mellon University, Aug 1996.
[CIPSO] Trusted Systems Interoperability Working Group, "Common IP
Security Option", ver. 2.3, 9 Mar 1993.
[Clark] D. Clark and D. Wilson, "A Comparison of Commercial and
Military computer Security Policies", in "Proceedings of the
IEEE Symposium on Security and Privacy", Apr 1987, pp. 184-
194.
[CSC1] U.S. DoD Computer Security Center, "Department of Defense
Trusted Computer System Evaluation Criteria", CSC-STD-001-
83, 15 Aug 1983. (Superseded by [DoD1].)
[CSC2] ---, "Department of Defense Password Management Guideline",
CSC-STD-002-85, 12 Apr 1985.
[CSC3] ---, "Computer Security Requirements: Guidance for Applying
the Department of Defense Trusted Computer System Evaluation
Criteria in Specific Environments", CSC-STD-003-85, 25 Jun
1985.
[CSOR] U.S. Department of Commerce, "General Procedures for
Registering Computer Security Objects", National Institute
of Standards Interagency Report 5308, Dec 1993.
[Daem] J. Daemen and V. Rijmen, "Rijndael, the advanced encryption
standard" in "Dr. Dobb's Journal", vol. 26, no. 3, Mar 2001,
pp.137-139.
[DC6/9] Director of Central Intelligence, "Physical Security
Standards for Sensitive Compartemented [sic] Information
Facilities ", DCI Directive 6/9, 18 Nov 2002.
[Denn] D. Denning, "A Lattice Model of Secure Information Flow", in
"Communications of the ACM", vol. 19, no. 5, May 1976, pp.
236-243.
[Denns] D. Denning and P. Denning, "Data Security" in "ACM Computing
Surveys", vol. 11, no. 3, Sep 1979, pp. 227-249.
[DH76] W. Diffie and M. Hellman, "New Directions in Cryptography"
in "IEEE Transactions on Information Theory", vol. IT-22,
no. 6, Nov 1976, pp. 644-654.
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[DoD1] U.S. DoD, "Department of Defense Trusted Computer System
Evaluation Criteria", DoD 5200.28-STD, 26 Dec 1985.
(Supersedes [CSC1].) (Superseded by DoD Directive 8500.1.)
[DoD2] ---, Directive 5200.28, "Security Requirements for Automated
Information Systems (AISs)", 21 Mar 1988. (Superseded by DoD
Directive 8500.1.)
[DoD3] ---, "X.509 Certificate Policy for the United States
Department of Defense", version 7, 18 Dec 2002.
[DoD4] ---, "NSA Key Recovery Assessment Criteria", 8 Jun 1998.
[DoD5] ---, Directive 5200.1, "DoD Information Security Program",
13 Dec 1996.
[DoD6] ---, "DoD Architecture Framework", Version 1, 30 Aug 2003.
[ElGa] T. El Gamal, "A Public-Key Cryptosystem and a Signature
Scheme Based on Discrete Logarithms" in "IEEE Transactions
on Information Theory", vol. IT-31, no. 4, 1985, pp. 469-
472.
[EMV1] Europay International S.A., MasterCard International
Incorporated, and Visa International Service Association,
"EMV '96 Integrated Circuit Card Specification for Payment
Systems", ver. 3.1.1, 31 May 1998.
[EMV2] ---, "EMV '96 Integrated Circuit Card Terminal Specification
for Payment Systems", ver. 3.1.1, 31 May 1998.
[EMV3] ---, EMV '96 Integrated Circuit Card Application
Specification for Payment Systems", ver. 3.1.1, 31 May 1998.
[F1037] U.S. General Services Administration, "Glossary of
Telecommunications Terms", FED STD 1037C, 7 Aug 1996.
[For94] W. Ford, "Computer Communications Security: Principles,
Standard Protocols and Techniques", ISBN 0-13-799453-2,
1994.
[For97] W. Ford and M. Baum, "Secure Electronic Commerce: Building
the Infrastructure for Digital Signatures and Encryption",
ISBN 0-13-476342-4, 1994.
[FP031] U.S. Department of Commerce, "Guidelines for Automatic Data
Processing Physical Security and Risk Management", Federal
Information Processing Standards Publication (FIPS PUB) 31,
Jun 1974.
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[FP039] ---, "Glossary for Computer Systems Security", FIPS PUB 39,
15 Feb 1976.
[FP041] ---, "Computer Security Guidelines for Implementing the
Privacy Act of 1974", FIPS PUB 41, 30 May 1975.
[FP046] ---, "Data Encryption Standard (DES)", FIPS PUB 46-3, 25 Oct
1999.
[FP074] ---, "Data Encryption Standard (DES)", FIPS PUB 46-3, 25 Oct
1999.
[FP081] ---, "DES Modes of Operation", FIPS PUB 81, 2 Dec 1980.
[FP087] ---, "Guidelines for ADP Contingency Planning", FIPS PUB 87,
27 Mar 1981.
[FP102] ---, "Guideline for Computer Security Certification and
Accreditation", FIPS PUB 102, 27 Sep 1983.
[FP113] ---, "Computer Data Authentication", FIPS PUB 113, 30 May
1985.
[FP140] ---, "Security Requirements for Cryptographic Modules", FIPS
PUB 140-2, 25 May 2001 (Change Notices 3 Dec 2002).
[FP151] ---, "Portable Operating System Interface (POSIX)--System
Application Program Interface [C Language]", FIPS PUB 151-2,
12 May 1993
[FP180] ---, "Secure Hash Standard", FIPS PUB 180-2, Aug 2000.
[FP185] ---, "Escrowed Encryption Standard", FIPS PUB 185, 9 Feb
1994.
[FP186] ---, "Digital Signature Standard (DSS)", FIPS PUB 186-2, 27
Jun 2000.
[FP188] ---, "Standard Security Label for Information Transfer",
FIPS PUB 188, 6 Sep 1994.
[FP191] ---, "Guideline for the Analysis of Local Area Network
Security", FIPS PUB 191, 9 Nov 1994.
[FP197] ---, "Advanced Encryption Standard", FIPS PUB 197, 26 Nov
2001.
[FPKI] U.S. Department of Commerce, "Public Key Infrastructure
(PKI) Technical Specifications: Part A--Technical Concept of
Operations", National Institute of Standards, 4 Sep 1998.
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[Gass] M. Gasser, "Building a Secure Computer System", Van Nostrand
Reinhold Company, New York, 1988, ISBN 0-442-23022-2.
[Gray] J. Gray and A. Reuter, "Transaction Processing: Concepts and
Techniques", Morgan Kaufmann Publishers, Inc., 1993.
[Hafn] K. Hafner and M. Lyon, "Where Wizards Stay Up Late: The
Origins of the Internet", Simon & Schuster, New York, 1996.
[Huff] G. Huff, "Trusted Computer Systems -- Glossary", MTR 8201,
The MITRE Corporation, Mar 1981.
[I3166] International Standards Organization, "Codes for the
Representation of Names of countries and Their Subdivisions
--Part 1: Country Codes", ISO 3166-1:1997.
---, --- "Part 2: Country Subdivision Codes", ISO/DIS 3166-
2.
---, --- "Part 3: Codes for Formerly Used Names of
Countries", ISO/DIS 3166-3.
[I7498] ---, "Information Processing Systems--Open Systems
Interconnection Reference Model--[Part 1:] Basic Reference
Model", ISO/IEC 7498-1. (Equivalent to ITU-T Recommendation
X.200.)
---, --- "Part 2: Security Architecture", ISO/IEC 7499-2.
---, --- "Part 4: Management Framework", ISO/IEC 7498-4.
[I7812] ---, "Identification cards--Identification of Issuers--Part
1: Numbering System", ISO/IEC 7812-1:1993
---, --- "Part 2: Application and Registration Procedures",
ISO/IEC 7812-2:1993.
[I9945] "Portable Operating System Interface for Computer
Environments", ISO/IEC 9945-1: 1990.
[IATF] U.S. DoD, "Information Assurance Technical Framework",
Release 3, NSA, Sep 2000. (See: IATF.)
[IDSAN] ---, "Intrusion Detection System Analyzer Protection
Profile", version 1.1, NSA, 10 Dec 2001.
[IDSSC] ---, "Intrusion Detection System Scanner Protection
Profile", version 1.1, NSA, 10 Dec 2001.
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[IDSSE] ---, "Intrusion Detection System Sensor Protection Profile",
version 1.1, NSA, 10 Dec 2001.
[IDSSY] ---, "Intrusion Detection System", version 1.4, NSA, 4 Feb
2002.
[Ioan] J. Ioannidis and M. Blaze, "The Architecture and
Implementation of Network Layer Security in UNIX", in "UNIX
Security IV Symposium", Oct 1993, pp. 29-39.
[ITSEC] "Information Technology Security Evaluation Criteria
(ITSEC): Harmonised Criteria of France, Germany, the
Netherlands, and the United Kingdom", ver. 1.2, U.K.
Department of Trade and Industry, Jun 1991.
[JCSP1] U.S. DoD, "Dictionary of Military and Associated Terms",
Joint Chiefs of Staff, JCS Pub. 1, 1 Apr 1984.
[Kahn] D. Kahn, "The Codebreakers: The Story of Secret Writing",
The Macmillan Company, New York, 1967.
[Knut] D. Knuth, Chapter 3 ("Random Numbers") in Volume 2
("Seminumerical Algorithms") of "The Art of Computer
Programming", Addison-Wesley, Reading, MA, 1969.
[Kuhn] M. Kuhn and R. Anderson, "Soft Tempest: Hidden Data
Transmission Using Electromagnetic Emanations", in David
Aucsmith, ed., "Information Hiding, Second International
Workshop, IH'98", Portland, Oregon, USA, 15-17 Apr 1998,
LNCS 1525, Springer-Verlag, ISBN 3-540-65386-4, pp. 124-142.
[Land] C. Landwehr, "Formal Models for Computer Security", in "ACM
Computing Surveys", vol. 13, no. 3, Sep 1981, pp. 247-278.
[Larm] J. Larmouth, "ASN.1 Complete", Open System Solutions, 1999
(a freeware book).
[M0404] U.S. Office of Management and Budget, "E-Authentication
Guidance for Federal Agencies", Memorandum M-04-04, 16 Dec
2003.
[Mene] A. Menezes et al, "Some Key Agreement Protocols Providing
Implicit Authentication" in "The 2nd Workshop on Selected
Areas in Cryptography", 1995.
[Moor] A. Moore et al, "Attack Modeling for Information Security
and Survivability", Carnegie-Mellon University / Software
Engineering Institute, CMU/SEI-2001-TN-001, Mar 2001.
[Murr] W. Murray, "Courtney's Laws of Security" in "Infosecurity
News", Mar/Apr 1993, p. 65.
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[N4001] National Security Telecommunications and Information System
Security Committee, "Controlled Cryptographic Items",
NSTISSI No. 4001, 25 Mar 1985.
[N4006] ---, "Controlled Cryptographic Items", NSTISSI No. 4006, 2
Dec 1991.
[N7003] ---, "Protective Distribution Systems", NSTISSI No. 7003, 13
Dec 1996.
[NCS01] National Computer Security Center, "A Guide to Understanding
Audit in Trusted Systems", NCSC-TG-001, 1 Jun 1988. (See:
Rainbow Series.)
[NCS03] ---, "Information System Security Policy Guideline", I942-TR-
003, ver. 1, Jul 1994.
[NCS04] ---, "Glossary of Computer Security Terms", NCSC-TG-004,
ver. 1, 21 Oct 1988. (See: Rainbow Series.)
[NCS05] ---, "Trusted Network Interpretation of the Trusted Computer
System Evaluation Criteria", NCSC-TG-005, ver. 1, 31 Jul
1987. (See: Rainbow Series.)
[NCS25] ---, "A Guide to Understanding Data Remanence in Automated
Information Systems", NCSC-TG-025, ver. 2, Sep 1991. (See:
Rainbow Series.)
[NCS25] ---, "A Guide to Understanding Data Remanence in Automated
Information Systems", NCSC-TG-025, ver. 2, Sep 1991. (See:
Rainbow Series.)
[NRC91] National Research Council, "Computers At Risk: Safe
Computing in the Information Age", National Academy Press,
1991.
[NRC98] F. Schneider, ed., "Trust in Cyberspace", National Research
Council, National Academy of Sciences, 1998.
[Park] D. Parker, "Computer Security Management", ISBN 0-8359-0905-
0, 1981
[Perr] T. Perrine et al, "An Overview of the Kernelized Secure
Operating System (KSOS)" in "Proceedings of the 7th DoD/NBS
Computer Security Conference", 24-26 Sep 1984.
[PGP] S. Garfinkel, "PGP: Pretty Good Privacy", O'Reilly &
Associates, Inc., Sebastopol, CA, 1995.
[PKCS] B. Kaliski, Jr., "An Overview of the PKCS Standards", RSA
Data Security, Inc., 3 Jun 1991.
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[PKC05] RSA Laboratories, "PKCS #5: Password-Based Encryption
Standard ", ver. 1.5, RSA Laboratories Technical Note, 1 Nov
1993.
[PKC07] ---, "PKCS #7: Cryptographic Message Syntax Standard", ver.
1.5, RSA Laboratories Technical Note, 1 Nov 1993.
[PKC10] ---, "PKCS #10: Certification Request Syntax Standard", ver.
1.0, RSA Laboratories Technical Note, 1 Nov 1993.
[PKC11] ---, "PKCS #11: Cryptographic Token Interface Standard",
ver. 1.0, 28 Apr 1995.
[R1108] S. Kent, "U.S. Department of Defense Security Options for
the Internet Protocol", RFC 1108, Nov 1991.
[R1135] J. Reynolds, "The Helminthiasis of the Internet", RFC 1135,
Dec 1989
[R1157] J. Case et al, "A Simple Network Management Protocol (SNMP)"
[version 1], STD 15, RFC 1157, May 1990.
[R1208] O. Jacobsen et al, "A Glossary of Networking Terms", RFC
1208, Mar 1991.
[R1281] R. Pethia et al, "Guidelines for Secure Operation of the
Internet", RFC 1281, Nov 1991.
[R1319] B. Kaliski, "The MD2 Message-Digest Algorithm", RFC 1319,
Apr 1992.
[R1320] R. Rivest, "The MD4 Message-Digest Algorithm", RFC 1320, Apr
1992.
[R1321] ---, "The MD5 Message-Digest Algorithm", RFC 1321, Apr 1992.
[R1334] B. Lloyd et al, "PPP Authentication Protocols", RFC 1334,
Oct 1992.
[R1413] M. St. Johns, "Identification Protocol", RFC 1413, Feb 1993.
[R1421] J. Linn, "Privacy Enhancement for Internet Electronic Mail,
Part I: Message Encryption and Authentication Procedures",
RFC 1421, Feb 1993.
[R1422] S. Kent, "Privacy Enhancement for Internet Electronic Mail,
Part II: Certificate-Based Key Management", RFC 1422, Feb
1993.
[R1455] D. Eastlake, III, "Physical Link Security Type of Service",
RFC 1455, May 1993.
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[R1457] R. Housley, "Security Label Framework for the Internet", RFC
1457, May 1993.
[R1492] C. Finseth, "An Access Control Protocol, Sometimes Called
TACACS", RFC 1492, Jul 1993.
[R1507] C. Kaufman, "DASS: Distributed Authentication Security
Service", RFC 1507, Sep 1993.
[R1510] J. Kohl et al, "The Kerberos Network Authentication Service
(V5)", RFC 1510, Sep 1993
[R1731] J. Myers, "IMAP4 Authentication Mechanisms", RFC 1731, Dec
1994.
[R1734] ---, "POP3 AUTHentication Command", RFC 1734, Dec, 1994.
[R1750] D. Eastlake, 3rd, et al, "Randomness Recommendations for
Security", Dec 1994.
[R1824] H. Danisch, "The Exponential Security System TESS: An
Identity-Based Cryptographic Protocol for Authenticated Key-
Exchange (E.I.S.S.-Report 1995/4)", RFC 1824, Aug 1995.
[R1828] P. Metzger et al, "IP Authentication using Keyed MD5", RFC
1828, Aug 1995.
[R1829] P. Karn et al, "The ESP DES-CBC Transform", RFC 1829, Aug
1995.
[R1848] S. Crocker et al, "MIME Object Security Services", RFC 1848,
Oct 1995.
[R1851] P. Karn et al, "The ESP Triple DES Transform", RFC 1851, Sep
1995.
[R1885] A. Conta et al, "Internet Control Message Protocol (ICMPv6)
for the Internet Protocol Version 6 (IPv6) Specification",
RFC 1885, Dec 1995.
[R1928] M. Leech et al, "SOCKS Protocol Version 5", RFC 1928, Mar
1996.
[R1938] N. Haller et al, "A One-Time Password System", RFC 1938, May
1996.
[R1983] G. Malkin, ed., "Internet Users' Glossary", FYI 18, RFC
1983, Aug 1996.
[R1994] W. Simpson, "PPP Challenge Handshake Authentication Protocol
(CHAP)", RFC 1994, Aug 1996.
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[R2026] S. Bradner, "The Internet Standards Process--Revision 3",
BCP009, RFC 2026, Mar 1994.
[R2065] D. Eastlake, 3rd, "Domain Name System Security Extensions",
RFC 2065, Jan 1997.
[R2078] J. Linn, "Generic Security Service Application Program
Interface, Version 2", RFC 2078, Jan 1997.
[R2084] G. Bossert et al, "Considerations for Web Transaction
Security", RFC 2084, Jan 1997.
[R2104] H. Krawczyk et al, "HMAC: Keyed-Hashing for Message
Authentication", RFC 2104, Feb 1997.
[R2137] D. Eastlake, 3rd, "Secure Domain Name System Dynamic
Update", RFC 2137, Apr 1997.
[R2138] C. Rigney et al, "Remote Authentication Dial In User Service
(RADIUS)", RFC 2138, Apr 1997.
[R2179] A. Gwinn, "Network Security For Trade Shows", RFC 2179, Jul
1997.
[R2195] J. Klensin et al, "IMAP/POP AUTHorize Extension for Simple
Challenge/Response", RFC 2195, Sep 1997.
[R2196] B. Fraser, "Site Security Handbook", FYI 8, RFC 2196, Sep
1997.
[R2202] P. Cheng et al, "Test Cases for HMAC-MD5 and HMAC-
SHA-1", RFC 2202, Sep. 1997.
[R2222] J. Myers, "Simple Authentication and Security Layer (SASL)",
RFC 2222, Oct 1997.
[R2223] J. Postel, "Instructions to RFC Authors", RFC 2223, Oct
1997.
[R2246] T. Dierks et al, "The TLS Protocol, Version 1.0", RFC 2246,
Jan 1999.
[R2267] P. Ferguson et al, "Network Ingress Filtering: Defeating
Denial of Service Attacks Which Employ IP Source Address
Spoofing", RFC 2267, Jan 1998
[R2315] B. Kaliski, "PKCS #7: Cryptographic Message Syntax, Version
1.5", RFC 2315, Mar 1998.
[R2323] A. Ramos, "IETF Identification and Security Guidelines", RFC
2323, 1 Apr 1998. [Intended for humorous entertainment
("please laugh loud and hard"); does not contain serious
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security information.]
[R2350] N. Brownlee et al, "Expectations for Computer Security
Incident Response", RFC 2350, Jun 1998.
[R2356] G. Montenegro et al, "Sun's SKIP Firewall Traversal for
Mobile IP", RFC 2356, Jun 1998.
[R2401] S. Kent et al, "Security Architecture for the Internet
Protocol", RFC 2401, Nov 1998.
[R2402] S. Kent et al, "IP Authentication Header", RFC 2402, Nov
1998.
[R2403] C. Madson et al, "The Use of HMAC-MD5-96 within ESP and AH",
RFC 2403, Nov 1998.
[R2404] C. Madson et al, "The Use of HMAC-SHA-1-96 within ESP and
AH", RFC 2404, Nov 1998.
[R2405] C. Madson et al, "The ESP DES-CBC Cipher Algorithm With
Explicit IV", RFC 2405, Nov 1998.
[R2406] S. Kent et al, "IP Encapsulating Security Payload (ESP)",
RFC 2406, Nov 1998.
[R2407] D. Piper, "The Internet IP Security Domain of Interpretation
for ISAKMP", RFC 2407, Nov 1998.
[R2408] D. Maughan et al, "Internet Security Association and Key
Management Protocol (ISAKMP)", RFC 2408, Nov 1998.
[R2409] D. Harkins and D. Carrel, "The Internet Key Exchange (IKE)",
RFC 2409, Nov 1998.
[R2410] R. Glenn et al, "The NULL Encryption Algorithm and Its Use
With IPsec", RFC 2410, Nov 1998.
[R2412] H. Orman, "The OAKLEY Key Determination Protocol", RFC 2412,
Nov 1998.
[R2451] R. Pereira et al, "The ESP CBC-Mode Cipher Algorithms", RFC
2451, Nov 1998.
[R2459] R. Housley et al, " Internet X.509 Public Key Infrastructure
Certificate and CRL Profile", RFC 2459, Jan 1999.
[R2504] E. Guttman et al, "Users' Security Handbook", RFC 2504, Feb
1999.
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[R2510] C. Adams et al, "Internet X.509 Public Key Infrastructure
Certificate Management Protocols", RFC 2510, Mar 1999.
[R2527] S. Chokhani et al, "Internet X.509 Public Key
Infrastructure, Certificate Policy and Certification
Practices Framework", RFC 2527, Mar 1999.
[R2536] D. Eastlake, "DSA KEYs and SIGs in the Domain Name System
(DNS)", RFC 2536, Mar 1999.
[R2560] M. Myers et al, "X.509 Internet Public Key Infrastructure
Online Certificate Status Protocol", RFC 2560, Jun 1999.
[R2570] J. Case et al, "Introduction to Version 3 of the Internet-
Standard Network Management Framework", RFC 2570, Apr 1999.
[R2574] U. Blumenthal et al, "User-based Security Model (USM) for
Version 3 of the Simple Network Management Protocol
(SNMPv3)", RFC 2574, Apr 1999.
[R2612] C. Adams et al, "The CAST-256 Encryption Algorithm", RFC
2612, Jun 1999.
[R2628] V. Smyslov, "Simple Cryptographic Program Interface", RFC
2628, Jun 1999.
[R2631] E. Rescorla, "Diffie-Hellman Key Agreement Method", RFC
2631, Jun 1999.
[R2634] P. Hoffman, ed., "Enhanced Security Services for S/MIME",
RFC 2634, Jun 1999.
[R2635] S. Hambridge et al, "Don't Spew: A Set of Guidelines for
Mass Unsolicited Mailings and Postings", RFC 2635, Jun 1999.
[R2773] R. Housley et al, "Encryption using KEA and SKIPJACK", RFC
2773, Feb 2000.
[R2898] B. Kaliski, PKCS #5: Password-Based Cryptography
Specification, Version 2.0", RFC 2898, Sep 2000.
[R3198] A. Westerinen et al, "Terminology for Policy-Based
Management", RFC 3198, Nov 2001.
[R3547] M. Baugher et al, "Group Domain of Interpretation", RFC
3547, Jul 2003.
[R3739] S. Santesson et al, "Internet X.509 Public Key
Infrastructure: Qualified Certificates Profile", RFC 3739,
Mar 2004.
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[R3740] T. Hardjono et al, "The Multicast Group Security
Architecture", RFC 3740, Mar 2004.
[R3748] B. Aboda, et al, "Extensible Authentication Protocol (EAP)",
RFC 3748, Jun 2004.
[R3753] J. Manner et al, ed's., "Mobility Related Terminology", RFC
3573, Jun 2004.
[R3820] S. Tuecke et al, "Internet X.509 Public Key Infrastructure
(PKI) Proxy Certificate Profile", RFC 3280, Jun 2004.
[Raym] E. Raymond, ed., "The On-Line Hacker Jargon File", ver.
4.0.0, 24 Jul 1996. (Also available as "The New Hacker's
Dictionary", 2nd edition, MIT Press, Sep 1993, ISBN 0-262-
18154-1. See: http://www.tuxedo.org/jargon/ for the latest
version.)
[Roge] H. Rogers, "An Overview of the Caneware Program", in
"Proceedings of the 10th National Computer Security
Conference", NIST and NCSC, Sep 1987.
[Russ] D. Russell et al, Chapter 10 ("TEMPEST") in "Computer
Security Basics", ISBN 0-937175-71-4, 1991.
[SAML] Organization for the Advancement of Structured Information
Standards (OASIS), "Assertions and Protocol for the OASIS
Security Assertion Markup Language (SAML)", version 1.1, 2
Sep 2003.
[Sand] R. Sandhu et al, "Role-Based Access Control Models", in
"IEEE Computer", vol. 29, no.2, Feb 1996, pp. 38-47.
[Schn] B. Schneier, "Applied Cryptography Second Edition", John
Wiley & Sons, Inc., New York, 1996.
[SDNS3] U.S. DoD, NSA, "Secure Data Network Systems, Security
Protocol 3 (SP3)", document SDN.301, Revision 1.5, 15 May
1989.
[SDNS4] ---, ---, "Security Protocol 4 (SP4)", document SDN.401,
Revision 1.2, 12 Jul 1988.
[SDNS7] ---, ---, "Secure data Network System, Message Security
Protocol (MSP)", document SDN.701, Revision 4.0, 7 Jun 1996,
with Corrections to Message Security Protocol, SDN.701, Rev
4.0", 96-06-07, 30 Aug, 1996.
[SET1] MasterCard and Visa, "SET Secure Electronic Transaction
Specification, Book 1: Business Description", ver. 1.0, 31
May 1997.
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[SET2] ---, "SET Secure Electronic Transaction Specification, Book
2: Programmer's Guide", ver. 1.0, 31 May 1997.
[SKEME] H. Krawczyk, H., "SKEME: A Versatile Secure Key Exchange
Mechanism for Internet", in "Proceedings of the 1996
Symposium on Network and Distributed Systems Security".
[SKIP] "SKIPJACK and KEA Algorithm Specifications", ver. 2.0, 22
May 1998 (available from NIST Computer Security Resource
Center).
[SP12] NIST, "An Introduction to Computer Security: The NIST
Handbook", Special Publication 800-12.
[SP14] M. Swanson et al (NIST), "Generally Accepted Principles and
Practices for Security Information Technology Systems", ---
800-14, Sep 1996.
[SP15] W. Burr et al (NIST), "Minimum Interoperability
Specification for PKI Components (MISPC), Version 1", ---
800-15, Sep 1997.
[SP22] A. Rukhin et al (NIST), "A Statistical Test Suite for Random
and Pseudorandom Number Generators for Cryptographic
Applications", --- 800-15, 15 May 2001.
[SP27] G. Stoneburner et al (NIST), "Engineering Principles for
Information Technology Security (A Baseline for Achieving
Security)", --- 800-27 Rev A, June 2004.
[SP28] W. Jansen (NIST), "Guidelines on Active Content and Mobile
Code", --- 800-28, Oct 2001.
[SP30] G. Stoneburner et al (NIST), "Risk Management Guide for
Information Technology Systems", --- 800-30, Oct 2001.
[SP31] R. Bace et al (NIST), "Intrusion Detection Systems", ---
800-31.
[SP32] D. Kuhn (NIST), "Introduction to Public Key Technology and
the Federal PKI Infrastructure ", --- 800-32, 26 Feb 2001.
[SP33] G. Stoneburner (NIST), "Underlying Technical Models for
Information Technology Security", --- 800-33, Dec 2001.
[SP37] R. Ross et al (NIST), "Guide for the Security Certification
and Accreditation of Federal Information Systems", --- 800-
37, May 2004
[SP41] J. Wack et al (NIST), "Guidelines on Firewalls and Firewall
Policy", --- 800-41, Jan 2002.
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[SP42] J. Wack et al (NIST), "Guideline on Network Security
Testing", --- 800-42, Oct 2003.
[SP56] NIST, "Recommendations on Key Establishment Schemes", Draft
2.0, --- 800-63, Jan 2003.
[SP57] NIST, "Recommendation for Key Management", Part 1 "General
Guideline" and Part 2 "Best Practices for Key Management
Organization", --- 800-57, Jan 2003.
[SP61] T. Grance et al (NIST), "Computer Security Incident Handling
Guide", --- 800-57, Jan 2003.
[SP63] W. Burr et al (NIST), "Electronic Authentication Guideline",
--- 800-63, Jun 2004
[SP67] W. Barker (NIST), "Recommendation for the Triple Data
Encryption Algorithm (TDEA) Block Cipher", --- 800-67, May
2004
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[X400] International Telecommunications Union--Telecommunication
Standardization Sector (formerly "CCITT"), Recommendation
X.400, "Message Handling Services: Message Handling System
and Service Overview".
[X500] ---, Recommendation X.500, "Information Technology--Open
Systems Interconnection--The Directory: Overview of
Concepts, Models, and Services". (Equivalent to ISO 9594-1.)
[X501] ---, Recommendation X.501, "Information Technology--Open
Systems Interconnection--The Directory: Models".
[X509] ---, Recommendation X.509, "Information Technology--Open
Systems Interconnection--The Directory: Authentication
Framework", COM 7-250-E Revision 1, 23 Feb 2001. (Equivalent
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[X519] ---, Recommendation X.519, "Information Technology--Open
Systems Interconnection--The Directory: Protocol
Specifications".
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[X520] ---, Recommendation X.520, "Information Technology--Open
Systems Interconnection--The Directory: Selected Attribute
Types".
[X680] ---, Recommendation X.680, "Information Technology--Abstract
Syntax Notation One (ASN.1)--Specification of Basic
Notation", 15 Nov 1994. (Equivalent to ISO/IEC 8824-1.)
[X690] ---, Recommendation X.690, "Information Technology--ASN.1
Encoding Rules--Specification of Basic Encoding Rules (BER),
Canonical Encoding Rules (CER) and Distinguished Encoding
Rules (DER)", 15 Nov 1994. (Equivalent to ISO/IEC 8825-1.)
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6. Security Considerations
This document mainly defines security terms and recommends how to use
them. It also provides limited tutorial information about security
aspects of Internet protocols, but it not describe in detail the
vulnerabilities of or threats to specific protocols and does not
definitively describe mechanisms that protect specific protocols.
7. Acknowledgments
Funding for the RFC Editor function is currently provided by the
Internet Society.
George Huff had a good idea! [Huff]
8. Author's Address
Please address all comments to:
Robert W. Shirey BBN Technologies
E-mail: rshirey@bbn.com Suite 400, Mail Stop 30/6B1
1300 Seventeenth Street North
Arlington, VA 22209-3801 USA
9. Full Copyright Statement
Copyright (C) The Internet Society (2004). This document is subject
to the rights, licenses and restrictions contained in BCP 78, and
except as set forth therein, the authors retain all their rights.
This document and the information contained herein are provided on an
"AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE IS SPONSORED
BY, THE INTERNET SOCIETY, AND THE INTERNET ENGINEERING TASK FORCE
DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT
LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION HEREIN WILL
NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY
OR FITNESS FOR A PARTICULAR PURPOSE.
Expiration Date: 20 February 2004.
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