Internet Engineering Task Force R. Shirey
INTERNET DRAFT GTE Internetworking
Expiration Date: 3 February 2000 3 August 1999
SECURITY GLOSSARY
<draft-shirey-security-glossary-00.txt>
Status of this Memo
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Abstract
This Glossary contains abbreviations, definitions, and explanations
for security-related terms. We propose that the Security Area
Directorate and the Security Area Advisory Group of the Internet
Engineering Task Force should review, approve, and issue this
Glossary as a consistent, self-supporting set of terminology to
improve the comprehensibility of Internet Standards Process
documents. To be clear and understandable, those documents should use
the same term or definition whenever and wherever the same concept is
mentioned. To improve international understanding, the documents
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should use terms in the plainest, dictionary sense. The documents
should use terms established in standards documents and other well-
founded publications and should avoid substituting private or newly
made-up terms. The documents should avoid terms that are proprietary
or otherwise favor a particular vendor, or that create a bias toward
a particular security technology or mechanism over other, competing
techniques that already exist or might be developed in the future.
Table of Contents
1. Introduction
2. Explanation of Paragraph Markings
3. Definitions
4. References
5. Security Considerations
6. Acknowledgements
7. Author's Address
8. Expiration Date
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1. Introduction
This Glossary seeks to improve the comprehensibility of Internet
documents by providing a consistent, self-supporting set of over
1,000 abbreviations, definitions, and explanations for terms related
to information system security. A few non-security, networking terms
have been included to make the Glossary self-contained, but more
complete glossaries of networking terms are available elsewhere
[R1208, R1983].
We propose that the Security Area Directorate and the Security Area
Advisory Group of the Internet Engineering Task Force should
undertake to review, approve, and issue this Glossary as an
Informational RFC (or perhaps eventually as a Best Practice RFC) for
use in writing Internet Standards Process documents (i.e., RFCs and
Internet-Drafts [R2026]). Toward that end, this Glossary marks each
term as either endorsed or deprecated for use. The key words "MUST",
"MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT",
"RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be
interpreted as described in RFC 2119.
This Glossary supports the goals of the Internet Standards Process:
o Clear, Concise, and Easily Understood Documentation
This Glossary seeks to improve comprehensibility of security-
related content of Internet Standards Process documents. That
requires the wording to be clear and understandable, and requires
the set of security-related terms and definitions to be consistent
and self-supporting. Also, the terminology needs to be uniform and
across all of the documents; the same term or definition needs to
be used whenever and wherever the same concept is mentioned.
Harmonization of existing documents need not be done immediately,
but is desirable to do when new versions of documents are issued
in the normal course of standards development and evolution.
o Technical Excellence
Just as Internet Standard protocols should operate effectively,
Internet Standards should use terminology accurately, precisely,
and unambiguously to enable them to be implemented correctly.
o Prior Implementation and Testing
Just as Internet Standard protocols require experience and
stability before adoption, Internet Standards Process documents
need to use well-established language. Using terms in their
plainest, dictionary sense (when appropriate) help to ensure
international understanding. The documents need to avoid using
private, made-up terms in place of generally-accepted terms from
standards and other publications. The documents need to avoid
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substituting new definitions that conflict with established ones.
The documents need to avoid using "cute" synonyms (e.g., see:
Green Book); no matter how popular a nickname may be in one
community, it is likely to cause confusion in another.
o Openness, Fairness, and Timeliness
Internet Standards Process documents need to avoid terms that are
proprietary or otherwise favor a particular vendor, or that create
a bias toward a particular 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 documents needs to be flexible and adaptable as the state
of Internet security art evolves.
2. Explanation of Paragraph Markings
Section 3 marks terms and definitions as follows:
o Capitalization: Only terms that are proper nouns are capitalized.
o Paragraph Marking: Definitions and explanations are stated in
paragraphs that are marked as follows:
- "I" identifies a recommended Internet definition.
- "N" identifies a recommended non-Internet definition.
- "O" identifies a definition that is not recommended for use but
is something that authors of Internet documents need to know.
- "C" identifies commentary or additional usage guidance,
including identifying deprecated terms.
The rest of Section 2 further explains those four markings.
2.1 Recommended Terms with an Internet Basis ("I")
The paragraph marking "I" (as opposed to "O") identifies a definition
that the Directorate recommends SHOULD be the first choice for use in
Internet documents. Terms and definitions of this type MAY be used in
Internet documents. However, some such definitions are preceded by an
indication of a contextual usage limitation (e.g., see:
certification), and the Directorate's endorsement of the term and
definition does not apply outside that context.
An "I" (as opposed to an "N") also indicates that the definition has
an Internet basis. That is, either the Internet Standards Process
[R2026] is authoritative for the term, or the term is sufficiently
generic that the Directorate can freely state a definition without
contradicting a non-Internet authority (e.g., see: attack).
For a proper noun, a "I" definition is only intended to provide
information in the style of a desktop encyclopedia; the authoritative
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definition is found elsewhere (e.g., see: Internet Protocol).
2.2 Recommended Terms with a Non-Internet Basis ("N")
The paragraph marking "N" (as opposed to "O") identifies a definition
that the Directorate recommends SHOULD be the first choice for the
term, if it is used at all in Internet documents. Terms and
definitions of this type MAY be used in Internet documents (e.g.,
see: X.509 public-key certificate).
However, an "N" (as opposed to an "I") indicates that the definition
has a non-Internet basis or origin; that is, the Internet Standards
Process is not authoritative for the definition. Many such
definitions are preceded by an indication of a contextual usage
limitation, and the Directorate's endorsement does not apply outside
that context. Also, some contexts are rarely if ever expected to
occur in a Internet document (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.
Many terms with "N" definitions are proper nouns (e.g., see: Computer
Security Objects Register). For these terms, the "N" definitions are
intended only to provide a basic information; the authoritative
definition is found elsewhere.
2.3 Other Definitions
For some terms, the "I" or "N" paragraph is followed by one or more
"O" paragraphs. The "O" indicates that the definition has a non-
Internet basis or origin and also indicates that the Directorate
recommends that the term SHOULD NOT be used in Internet documents,
except possibly in cases where the term is specifically identified by
as non-Internet. For example, some Internet Standards Process
document might was to mention BCA (see: brand certification
authority) as an example to illustrate some concept; in that case,
the document should specifically refer to it as "SET(trademark) BCA"
and give the SET definition.
For many terms that have a definition published by a non-Internet
authority--government (see: object reuse), industry (see: Secure Data
Exchange), national (see: key authentication), or international (see:
data confidentiality)--this Glossary provides an "N" definition,
recommended for use in Internet documents. But in other cases, the
available non-Internet definition is inadequate or other
inappropriate for Internet Standards use. It may be narrow or
outdated, or it need clarification by substituting more careful
wording or more explanatory wording, based on other terms that
defined here. In those cases, this Glossary provides an "I"
definition that supersedes the non-Internet definition.
In cases where this Glossary provides a "I" definition to supersede a
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non-Internet definition that is some kind of standard, the substitute
is intended to subsume the meaning of the non-Internet definition and
not conflict with it. For example, the "O" definition of "security
service" deals narrowly with only communication services provided by
layers in the OSI model and is inadequate for the full range of
Internet Standards Process usage; the "I" definition can be used in
more situations and for more kinds of service. However, the "O"
definition is listed to make authors of Internet documents aware of
situations in which the term is used narrowly.
This Glossary attempts to substitute understandable English that does
not contradict any non-Internet authority. Still, terminology differs
between the standards of the American Bar Association, OSI, SET, the
U.S. Department of Defense, and other authorities, and this Glossary
probably is not exactly aligned with all of them.
2.4 Commentary and Additional Guidance
The paragraph marking "(C)" identifies text that is advisory or
tutorial. This text MAY be reused in other Internet documents. This
text is not intended to be authoritative, but is provided to clarify
the definitions and to enhance this Glossary so that Internet
security novices can use it as a tutorial.
2.5 Deprecated Terms
If the Directorate recommends that a term SHOULD NOT be used at all,
then that term has only a "C" paragraph that states that "Internet
Standards Process documents SHOULD NOT use" the term. A rationale is
given for each such negative recommendation (e.g., see: Green Book).
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3. Definitions
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 [X680].
(C) OSI standards use ASN.1 to specify data formats for protocols.
OSI defines functionality in layers, and information objects at
higher layers are abstractly defined to be implemented with
objects at lower layers. A higher layer may define transfers of
abstract objects between computers, and a lower layer may define
transfers concretely as strings of bits. Syntax is needed to
define abstract objects, and encoding rules (see: Basic Encoding
Rules) are needed to transform between abstract objects and bit
strings.
(C) 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
See: access control center.
access
(I) The ability and means to communicate with or otherwise
interact with a system in order to use system resources to either
handle information or gain knowledge of the information the system
contains.
(O) "A specific type of interaction between a subject and an
object that results in the flow of information from one to the
other." [NCS04]
(C) In this glossary, "access" is intended to cover any ability to
communicate with a system, including one-way communication in
either direction. In actual practice, however, entities outside a
security perimeter that 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.
access control
(I) Protection of system resources against unauthorized access; a
process by which use of system resources is regulated according to
a security policy and is permitted by only authorized entities
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(users, programs, processes, or other systems) according to that
policy. (Also see: access, access control service.)
(O) "The prevention of unauthorized use of a resource, including
the prevention of use of a resource in an unauthorized manner."
[I7498 Part 2]
access control center (ACC)
(I) A computer containing a database with entries that define a
security policy for an access control service.
(C) An ACC is sometimes used in conjunction with a key center to
implement access control in a key distribution system for
symmetric cryptography.
access control list (ACL)
(I) A mechanism that implements access control for a system
resource by enumerating the identities of the system entities that
are permitted to access the resource. (Compare with: capability.)
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; in short, protection of system resources against
unauthorized access. (Also see: access control, discretionary
access control, identity-based security policy, mandatory access
control, rule-based security policy.)
(C) This service includes protecting against use of a resource in
an unauthorized manner by an entity that is authorized to use the
resource in some other manner.
access mode
(I) A distinct type of data processing operation--such as read,
write, append, or execute--that potentially can be performed on an
object in a computer system.
accountability
(I) The property of a system (including all of its system
resources) that ensures that the actions of a system entity may be
traced uniquely to that entity, which can be held responsible for
its actions. (Also see: audit service.)
(C) Accountability permits detection and subsequent investigation
of security breaches.
accreditation
(I) An administrative declaration by a designated authority that
an information system is approved to operate in a particular
security configuration with a prescribed set of safeguards. (Also
see: certification.)
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(C) Accreditation is based on certification of the system's
security mechanisms. These terms are used more in the U.S.
Department of Defense and other government agencies than in
commercial organizations. However, the concepts apply any place
where managers must deal with and accept responsibility for
security risks, and the American Bar Association is developing
accreditation criteria specifically for CAs.
ACL
See: access control list.
acquirer
(N) SET usage: "The financial institution that establishes an
account with a merchant and processes payment card authorizations
and payments." [SET1]
(O) "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, and ANSI
X9.8 and X9.24]
active attack
See: (secondary definition in) attack.
active wiretapping
See: (secondary definition in) wiretapping.
add-on security
(I) "The retrofitting of protection mechanisms, implemented by
hardware or software, after the [automatic data processing] system
has become operational." [FP039]
administrative security
(I) Management procedures and constraints to prevent unauthorized
access to a system. (Also see: security architecture.)
(O) "The management constraints, operational procedures,
accountability procedures, and supplemental controls established
to provide an acceptable level of protection for sensitive data."
[FP039]
(C) Examples include clear delineation and separation of duties,
and configuration control.
Advanced Encryption Standard (AES)
(N) A future FIPS publication being developed by NIST to succeed
DES. Intended to specify an unclassified, publicly-disclosed,
symmetric encryption algorithm, available royalty-free worldwide.
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adversary
(I) An entity that attacks, or is a threat to, a system.
aggregation
(I) A circumstance in which a collection of information items must
be classified at a higher security level than any of the
individual items that comprise it.
AH
See: Authentication Header
alias
(I) A name that an entity uses in place of its real name, usually
for the purpose of either anonymity or deception.
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. (Also see: cryptographic algorithm.)
American National Standards Institute (ANSI)
(N) A private, not-for-profit association of users, manufacturers,
and other organizations, that administers U.S. private sector
voluntary standards.
(C) ANSI is the sole U.S. representative to the two major non-
treaty international standards organizations, ISO and, via the
U.S. National Committee (USNC), the International Electrotechnical
Commission (IEC).
anonymous
(I) The condition of having a name that is unknown or concealed.
(C) An application may require security services that maintain
anonymity of users or other system entities, perhaps to preserve
their privacy or shield 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 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.
archive, archive management
(I) (1.) 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 with: backup.) (2.) Verb: to store
data in such a way. (Compare with: back up.)
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(C) 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 must 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 Network, a pioneer packet-
switched network that was built in the early 1970s under contract
to the U.S. Government led to the development of today's Internet,
and was decommissioned in June 1990.
ASN.1
See: Abstract Syntax Notation One.
association
(I) A cooperative relationship between system entities, usually
for the purpose of transferring information between them. (Also
see: security association.)
assurance
(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; procedures that ensure a
system is developed and operated as intended by its security
policy.
assurance level
(I) Evaluation usage: A specific level on a hierarchical scale
representing successively increased confidence that a target of
evaluation adequately fulfills the requirements (e.g., see:
TCSEC).
asymmetric cryptography
(I) A modern branch of cryptography in which the algorithms employ
a key pair (a public key and a private key) and use a different
key of the pair for different steps of the algorithm. (Popularly
known as "public-key cryptography".)
(C) Asymmetric algorithms have key management advantages over
equivalently strong symmetric ones. First, one key of the pair
does not need to be known by anyone but its owner; so it can more
easily be kept secret. Second, although the other key of the pair
must be shared by all entities that use the algorithm, that key
does not need to be kept secret from other entities; so the key
distribution part of key management can be done more easily.
(C) For encryption: In an asymmetric encryption algorithm (e.g.,
see: RSA), when Alice wants to ensure confidentiality for data she
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sends to Bob, she encrypts the information with a public key
provided by Bob. Only Bob has the matching private key that is
needed to decrypt the data.
(C) For signature: 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 (create a digital signature from) the data. To
verify the signature, Bob uses the matching public key that Alice
has provided.
(C) For key agreement: In an asymmetric key agreement algorithm
(e.g., see: Diffie-Hellman), Alice and Bob each send their own
public key to the other person. Then each uses their own private
key and the other's public key to compute the new key value.
attack
(I) An assault on system security that derives from an intelligent
threat, i.e., an intelligent act that is a deliberate attempt
(especially in the sense of a method or approach) to evade
security services and violate the security policy of a system.
(Also see: penetration, violation, vulnerability.)
(C) An "active attack" attempts to alter system resources or
affect their operation. A "passive attack" attempts to learn or
make use of information (e.g., see: wiretapping) does not affect
system resources.
(C) An "insider attack" (or inside attack) is an attack initiated
by an entity inside the security perimeter, i.e., by an entity
that is authorized to access system resources but uses them in a
way not approved by those who granted the authorization. An
"outsider attack" (or outside attack) is initiated from outside
the perimeter, by an unauthorized or illegitimate user of the
system. In the Internet, potential outside attackers range from
amateur pranksters to organized criminals, international
terrorists, and hostile governments.
attribute authority
(I) A CA that issues attribute certificates.
attribute certificate
(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. [X509]
(O) "A set of attributes of a user together with some other
information, rendered unforgeable by the digital signature created
using the private key of the CA which issued it." [X509]
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(C) 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.
(C) 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 issues the
associated public-key certificate.)
audit service
(I) A security service that records information needed to
establish accountability for system events and the actions of
system entities that cause them. (Also see: security audit.)
audit trail
See: security audit trail.
authentic signature
(I) A signature (particularly 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. (Also see: authentication.)
(C) This definition is narrower than in general English usage,
where this term usually means "to prove genuine"; for example, an
art expert authenticates a Michelangelo painting. Although we
might be tempted to speak similarly of authenticating a digital
signature or digital certificate, Internet Standards Process
documents SHOULD NOT use this term in that way in the context of
asymmetric cryptography. Instead, we "sign" and then "verify"
digital signatures, and we "issue" and then "validate" digital
certificates. (See: validate vs. verify.)
authentication
(I) The process of verifying an identity claimed by or for a
system entity. (Also see: authentication exchange, authentication
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information, data origin authentication, peer entity
authentication.)
(C) An authentication process consists of two steps:
- Identification step: Presenting an identifier to the security
system. (Identifiers must 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 corroborates the binding between the entity
and the identifier. (Also see: verification.)
(C) See: ("relationship between data integrity service and
authentication services" in) data integrity service.
authentication code
(C) Internet Standards Process documents SHOULD NOT use this term
because it is sometimes misleading defined as a synonym for
cryptographic checksum. The word "authentication" is misleading
because the mechanism involved usually serves a data integrity
function rather than an authentication function. (Also see:
message authentication code.)
Authentication Header (AH)
(I) An Internet IPsec protocol [R2402] designed to provide
connectionless data integrity service and data origin
authentication service for IP datagrams, and (optionally) to
provide protection against replay attacks.
(C) 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. The values of such fields
cannot be protected by AH. Thus, protection of the IP header by AH
is only partial.
(C) AH may be used alone, or in combination with the IPsec ESP
protocol, 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 the same security services as AH, and ESP
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.
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authentication exchange
(I) A mechanism to verify the identity of an entity by means of
information exchange.
(O) "A mechanism intended to ensure the identity of an entity by
means of information exchange." [I7498 Part 2]
authentication information
(I) Information used to verify an identity claimed by or for an
entity. (Also see: authentication, credential.)
(C) Authentication information may exist as, or be derived from,
one of the following:
- Something the entity knows. (Also see: password).
- Something the entity possesses. (Also see: token.)
- Something the entity is. (Also see: biometric authentication.)
authentication service
(I) A security service that verifies an identity claimed by or for
an entity. (Also see: authentication.)
(C) 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. (Also see: authenticate, authentication, validate vs.
verify)
authority
See: attribute authority, certification, registration authority
authority revocation list (ARL)
(I) A data structure that enumerates digital certificates that
were issued to certification authorities but have been invalidated
by their issuer prior to when they were scheduled to expire (see:
certificate expiration). (Also see: X.509 authority revocation
list.)
authorize, authorization
(I) (1.) To "authorize" means to grant a right or permission to a
system entity to access a system resource. (2.) An "authorization"
is a right or a permission that is granted. (Also see: privilege.)
(3.) An "authorization process" is a procedure for granting such
rights.
(O) SET usage: "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
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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]
availability
(I) The property of a system or a system resource being accessible
and usable upon demand by an authorized system entity, according
to performance specifications for the system; i.e., a system is
available if it provides services according to the system design
whenever users request them. (Also see: critical; denial of
service.)
(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.
(C) This service addresses the security concerns engendered 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.
back door
(I) A hardware or software mechanism that provides access to a
system and its resources by other than the usual procedure and,
usually, is not publicly known. (Also see: trap door.)
(C) For example, a way to access a computer other than through the
legitimate login procedure.
back up vs. backup
(I) Noun: "backup": a reserve copy of data that is stored
separately from the original, for use if the original becomes lost
or damaged. (Compare with: archive. Also see: contingency plan.)
(I) Verb: "back up": to store data in such a way. (Compare with:
archive.)
baggage
(O) SET usage: 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]
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bandwidth
(I) Commonly used to mean the capacity of a communication channel
to pass data through the channel in a given amount of time.
(Usually expressed in bits per second.)
bank identification number (BIN)
(I) The digits of a credit card number that identify the issuing
bank. (Also see: primary account number.)
(O) SET usage: 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 (eight-bit values) [X690]. (Also see: Distinguished
Encoding Rules.)
bastion host
(I) A strongly protected computer that is in a network protected
by a firewall (or is part of a firewall) and is the only host (or
one of only a few hosts) in the network that can be directly
accessed from networks on the other side of the firewall.
(C) 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 must 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 have forwarding
built in (like DNS or SMTP); other services (like TELNET and FTP)
require a proxy server on the bastion host.
BCA
See: brand certification authority.
BCI
See: brand CRL identifier.
Bell-LaPadula Model
(N) A formal, mathematical, state-transition model of security
policy for multilevel-secure computer systems, devised by David
Bell and Leonard LaPadula at The MITRE Corporation in 1973.
(C) The model separates computer system elements into a set of
subjects and a set of 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
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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.
(C) In this model, a multilevel-secure system satisfies several
rules, including the following:
- "Confinement property" (also called "*-property"): A subject
has write access to an object only if the clearance of the
subject is dominated by the classification of the object.
- "Simple security property": A subject has read access to an
object only if the clearance of the subject dominates the
classification of the object.
- "Tranquillity property": The classification of an object does
not change while the object is being processed by the system.
BER
See: Basic Encoding Rules.
BIN
See: bank identification number.
bind
(I) To inseparably associate by applying some mechanism, such as
when a CA uses a digital signature to bind together a subject and
a public key in a public-key certificate.
biometric authentication
(I) A method of generating authentication information for a person
by digitizing measurements of a physical characteristic, such as
fingerprint patterns, hand shape, retina pattern, speech sounds,
or handwriting pattern.
bit
(I) The smallest unit of information storage; a contraction of the
term "binary digit"; one of two symbols--"0" (zero) and "1" (one)
--that are used to represent binary numbers.
BLACK
(I) Designation for information system equipment or facilities
that handle (and for data that contains) only ciphertext (or,
depending on the context, only unclassified information), and for
such data itself. This term derives from U.S. Government COMSEC
terminology. (Compare with: RED. Also see: RED/BLACK separation.)
block cipher
(I) An encryption algorithm that breaks plaintext into fixed-size
segments and uses the same key to transform each plaintext segment
into a fixed-size segment of ciphertext. (Also see: mode, stream
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cipher.)
(C) For example, Blowfish, DEA, IDEA, RC2, and SKIPJACK. However,
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.
Blowfish
(N) A symmetric block cipher with variable-length key (32 to 448
bits) designed in 1993 by Bruce Schneier [Schn] as an unpatented,
license-free, royalty-free replacement for DES or IDEA.
brand
(I) A distinctive mark or name that identifies a product or
business entity.
(O) SET usage: The name of a payment card. 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 usage: A CA owned by a payment card brand, such as
MasterCard, Visa, or American Express. [SET2] (Also see:
certification hierarchy, SET.)
brand CRL identifier (BCI)
(O) SET usage: A digitally signed list, issued by the BCA, of the
names of CAs for which CRLs must be processed when verifying
signatures in SET messages. [SET2]
break
(I) Cryptographic usage: 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. (This term applies to encrypted
data or, more generally, to a cryptographic algorithm or
cryptographic system.)
bridge
(I) A computer that is a gateway between two networks (usually two
LANs) at OSI layer 2. (Compare with: router.)
browser
(I) An client computer program that can retrieve and display
information from servers on the World Wide Web.
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(C) For example, Netscape's Navigator and Communicator, and
Microsoft's Explorer.
brute force
(I) A cryptanalysis approach or other kind of attack method
involving an exhaustive procedure that tries all possibilities,
one-by-one.
(C) For example, for ciphertext where the analyst already knows
the decryption algorithm, the brute force approach to finding the
original plaintext is to decrypt the message with every possible
key.
byte
(I) A unit of eight bits; also called an "octet", especially in
OSI standards.
CA
See: certification authority.
CA certificate
(I) "A [digital] certificate for one CA issued by another CA."
[X509]
(C) 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."
call back
(I) An authentication technique for terminals that remotely access
a computer via telephone lines; the host system disconnects the
caller and then calls back on a telephone number that was
previously authorized for that terminal.
capability
(I) A token, usually an unforgeable data value (sometimes called a
"ticket") 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 named or indicated by the token. (Compare with: access
control list.)
(C) This concept can be implemented as a digital certificate.
(Also see: attribute certificate.)
CAPI
See: "cryptographic application programming interface".
CAPSTONE chip
(N) An integrated circuit (the Mykotronx, Inc. MYK-82) with a Type
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II cryptographic processor that implements SKIPJACK, KEA, DSA,
SHA, and basic mathematical functions to support asymmetric
cryptography, and includes the key escrow feature of the CLIPPER
chip. (Also see: FORTEZZA card.)
card
See: cryptographic card, FORTEZZA card, payment card, PC card,
smart card, token.
card backup
See: token backup.
card copy
See: token copy.
card restore
See: token restore.
cardholder
(I) An entity that has been issued a card.
(O) SET usage: "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 usage: 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 usage: A CA responsible for issuing digital certificates
to cardholders and operated on behalf of a payment card brand, an
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 C(arlisle) A(dams) and
S(tafford) T(avares).
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category
(I) A grouping of sensitive information items to which a non-
hierarchical restrictive security label is applied to increase
protection of the data. (Also see: compartment.)
CAW
See: certification authority workstation.
CBC
See: cipher block chaining.
CCA
See: cardholder certification authority.
CCITT
(N) Acronym for French translation of International Telephone and
Telegraph Consultative Committee. Now renamed ITU-T.
CERT
See: computer emergency response team.
certificate
(I) In common English usage, a document that attests to the truth
of something or the ownership of something.
(C) Security usage, see: digital certificate, X.509 certificate.
(C) PKI usage, see: public-key certificate.
certificate authority
(C) This term looks like imprecise use of a term standardized by
X.509 and, therefore, Internet Standards documents SHOULD NOT use
this term as a synonym for "certification authority".
certificate chain
(C) Internet Standards Process documents SHOULD NOT use this term
because it duplicates the meaning of a standardized term. Instead,
use "certification path".
certificate chain validation
(C) Internet Standards Process documents SHOULD NOT use this term
because 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. (Also 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. (Also see: issue.)
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certificate expiration
(I) The event that occurs when a certificate ceases to be valid
because its assigned lifetime has been exceeded. (Also see:
certificate revocation, validity period.)
certificate extension
See: extension.
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.
(Also see: archive management, key management, security
architecture, token management, certificate management.)
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 with:
certification practice statement.)
(C) A certificate policy can help a certificate user 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 goods within a given price range." [R2527]
(C) 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.
(C) SET usage: Every 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. (Also 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.
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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
(I) The act or process by which an existing public-key certificate
has its public key value changed by issuing a new certificate with
a different (usually new) public key. (Also see: certificate
renewal, certificate update, rekey.)
(C) 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".
(O) MISSI usage: To rekey a MISSI X.509 public-key certificate
means that the issuing authority creates a new certificate that is
identical to the old one, except the new one has a new, different
KEA key; or a new, different DSS key; or 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.
certificate renewal
(I) The act or process by which the validity of the data binding
asserted by an existing public-key certificate is extended in time
by issuing a new certificate. (Also see: certificate rekey,
certificate update.)
(C) For an X.509 public-key certificate, this term means that the
validity period is extended 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
(C) Internet Standards Process documents SHOULD NOT use this term
because 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;
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usually stated with a revocation date.
(C) In X.509, a revocation is announced to potential certificate
users by a CRL that mentions the certificate. Revocation and
listing on a CRL is only necessary before certificate expiration.
certificate revocation list (CRL)
(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). (Also see:
X.509 certificate revocation list.)
certificate revocation tree
(I) A mechanism for distributing notice of certificate revocations
(as an alternative to issuing a CRL), using a tree of hash results
that is signed by the tree's issuer.
certificate serial number
(I) An integer value that is unambiguously associated with a
digital certificate issued by a CA and that is unique within the
domain of that CA. [X509]
certificate status responder
(N) FPKI usage: A trusted on-line server that acts for a CA to
provide authenticated certificate status information to
certificate users. [FPKI]
certificate update
(I) The act or process by which data items bound in an existing
public-key certificate, especially authorizations granted to the
subject, are changed by issuing a new certificate. (Also see:
certificate rekey, certificate renewal.)
(C) 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 the old certificate usually
must be revoked. (Otherwise, the process is only a "certificate
rekey" or "certificate renewal".)
certificate user
(I) A system entity that depends on the validity of information
(such as another entity's public key value) provided by a digital
certificate. (Also see: relying party.)
(O) "An entity that needs to know, with certainty, the public key
of another entity." [X509]
(C) The system entity may be a human being or an organization, or
a device or process under the control of a human or an
organization.
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(C) Internet Standards Process documents SHOULD NOT use this term
as a synonym for the "subject" of a certificate.
certificate validation
(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.)
(C) To validate a certificate, a certificate user checks that the
certificate is properly formed and signed and currently in force:
- Signature: Employs the issuer's public key to verify the
digital signature of the CA who issued the certificate in
question. If the key is obtained from the issuer's own public-
key certificate, that certificate also must be validated. 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.
- 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.
- 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 in valid. (CRLs themselves require a
similar validation process.)
certification
(I) Information system usage: Technical evaluation of an
information system's security features and other safeguards
(usually made in support of an accreditation action) to establish
the extent to which the system's design and implementation meet
specified security requirements.
(I) Public key usage: 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 owns the key. (In
addition to binding a key with a name, a public-key certificate
may bind those items with other restrictive or explanatory data
items; e.g., see: X.509 public-key certificate.)
(O) SET usage: "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]
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certification authority (CA)
(I) An entity that issues digital certificates (especially X.509
certificates) and vouches for the binding between the data items
in a certificate.
(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]
(C) Certificate users depend on the validity of information
provided by a certificate. Thus, a CA must 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)
(I) A computer system that enables a CA to issue digital
certificates and supports other certificate management functions
as required.
certification hierarchy
(I) A tree-structured (loop-free) topology of relationships among
CAs and the entities to whom the authorities issue public-key
certificates. (Also see: hierarchical PKI.)
(C) In this structure, one CA is the top CA, the highest level of
the hierarchy. (Also see: root.) All certificate users base path
validations on the top CA's public key. The top CA 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. The CAs at the
bottom of the hierarchy issue certificates only to entities that
are not CAs (see: end entity). Thus, all certification paths begin
at the top CA and descend through one or more levels of other CAs.
(O) MISSI usage: A MISSI certification hierarchy has three or four
levels:
- A CA at the highest level, the top CA, is a "policy approving
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".
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(O) PEM usage: A PEM certification hierarchy has three levels
[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".
(O) SET usage: A SET certification hierarchy has three or four
levels:
- 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
(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. (Also see:
certificate validation, valid certificate.)
(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." [X509, R2527]
(C) 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.
(C) The word "particular", in the X.509 quotation in the previous
paragraph, points out that a certification path that can be
validated by one certificate user might not be able to be
validated by another. (See: certificate validation.) That is
because either the first certificate must be a trusted certificate
(it might be a root certificate) or the signature on the first
certificate must be verified by a trusted key (it might be a root
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key), and that element of trust is relative to the user.
certification policy
(C) Internet Standards Process documents SHOULD NOT use this term.
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] (Compare with:
certificate policy.)
(C) 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 employs 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]
(C) 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 a single CPS may support multiple
certificate policies, which may be used for different application
purposes or by different user communities. 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 (a public key)
(I) To certify a public key means to issue a public-key
certificate that vouches for the truth and accuracy of the binding
between a subject's name or title and a public key. (Also see:
certification.)
(C) A description of the measures employed by a CA to verify the
identity of the subject or the ownership of the public key should
be included in the CA's CPS.
CFB
See: cipher feedback.
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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 the challenge and a secret key. [R1994]
(Also 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 must be computed in response
to an unpredictable challenge value.
channel
(I) An information transfer path within a system. (Also see:
covert channel.)
checksum
(I) A value that (a) is computed by a function that is dependent
on the contents of a data set and (b) is stored or transmitted
together with the data, for the purpose of detecting changes in
the data. (Also see: cyclic redundancy check, data integrity
service, error detection code, hash, protected checksum.)
(C) To gain confidence that a data set has not been changed, an
entity that later uses the data can compute a checksum and compare
it with the checksum that was stored or transmitted with the data.
(C) Computer systems and networks employ 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 must be
well-chosen (see: cryptographic hash), and the checksum result
must be protected (see: digital signature, keyed hash).
chosen-ciphertext attack
(I) A cryptanalysis approach in which the analyst tries to
determine the key from knowledge of plaintext that corresponds to
ciphertext selected (dictated) by the analyst.
chosen-plaintext attack
(I) A cryptanalysis approach in which the analyst tries to
determine the key from knowledge of ciphertext that corresponds to
plaintext selected (dictated) by the analyst.
CIK
See: cryptographic ignition key.
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cipher
(I) A cryptographic algorithm for encryption and decryption.
cipher block chaining (CBC)
(I) An block cipher mode that enhances electronic codebook mode by
chaining together blocks of ciphertext it produces [FP081].
(C) 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)
(I) An block cipher mode that enhances electronic code book mode
by chaining together the blocks of ciphertext it produces and
operating on plaintext segments of variable length less than or
equal to the block length [FP081].
(C) This mode operates by using the previously generated
ciphertext segment as the algorithm's input (i.e., by "feeding
back" the ciphertext) 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.
ciphertext
(I) Data that has been transformed by encryption so that its
semantic information content (i.e., its meaning) is no longer
intelligible or directly available. (Also see: cleartext,
plaintext.)
(O) "Data produced through the use of encipherment. The semantic
content of the resulting data is not available." [I7498 Part 2]
ciphertext-only attack
(I) A cryptanalysis approach in which the analyst tries to
determine the key solely from knowledge of intercepted ciphertext
(although the analyst may also know other clues, such as the
cryptographic algorithm, the language in which the plaintext was
written, the subject matter of the plaintext, and some probable
plaintext words.)
CIPSO
See: Common IP Security Option.
CKL
See: compromised key list.
class 2, 3, 4, or 5
(O) U.S. Department of Defense usage: Levels of assurance based on
risk and value of information to be protected [DOD3].
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- Class 2: For handling low-value information (unclassified, not
mission-critical, or low monetary value) or protection of
system-high information in low- to medium-risk environment.
- Class 3: For handling medium-value information in low- to
medium-risk environment. Typically requires identification of a
system entity as a legal person, rather than merely a member of
an organization.
- Class 4: For handling medium- to high-value information in any
environment. Typically requires identification of an entity as
a legal person, rather than merely a member of an organization,
and a cryptographic hardware token for protection of keying
material.
- Class 5: For handling high-value information in a high-risk
environment.
classification, classification level
(I) A grouping of classified information to which a hierarchical,
restrictive security label is applied to increase protection of
the data; or the level of protection that must be applied to that
information. (See: security level.)
classified
(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. (Also see: unclassified.)
(C) The term is mainly used in government, especially in the
military, although the concept underlying the term also applies
outside government. In the U.S. Department of Defense, for
example, it means information that has been determined pursuant to
Executive Order 12958 ("Classified National Security Information",
13 December 1996) or any predecessor order to require protection
against unauthorized disclosure and is marked to indicate its
classified status when in documentary form.
clearance, clearance level
(I) The security level of information to which a security
clearance authorizes a person to have access.
cleartext
(I) Data in which the semantic information content (i.e., the
meaning) is intelligible or is directly available. (Compare with:
plaintext.)
(O) "Intelligible data, the semantic content of which is
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available." [I7498 Part 2]
(C) Internet Standards Process documents SHOULD NOT use this term
loosely as a synonym for "plaintext", the input to an encryption
operation. That is not an equivalent term, because the plaintext
input to encryption may itself be ciphertext that was output from
another operation. (See: superencryption.)
client
(I) A system entity that requests and makes use of a service
provided by another system entity, which is called a server.
(C) 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.
CLIPPER chip
(N) The Mykotronx, Inc. MYK-82, an integrated microcircuit with a
cryptographic processor that implements the SKIPJACK encryption
algorithm and supports key escrow. (Also see: CAPSTONE, Escrowed
Encryption Standard.)
(C) The key escrow scheme involves a SKIPJACK key common to all
chips, a serial number unique to the chip, and a second SKIPJACK
key that is unique to the chip and unlocks 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) DoD usage: A system environment that meets both of the
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] (Also see: open
security environment.)
color change
(I) In a system that is 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.
Common Criteria for Information Technology Security
(N) Also known as "the Common Criteria". An ISO standard for
evaluating information technology products and systems, such as
operating systems, computer networks, distributed systems, and
applications. It states requirements for security functions and
for assurance measures.
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(C) 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" (FC)
and its precursor, the TCSEC. The U.S. Government intends that
this standard will supersede both the TCSEC and FIPS PUB 140-1.
(Also see: NIAP.)
(C) 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.
(C) 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 [CCIB] is identical to the Final Committee Draft for
International Standard 15408 being balloted within ISO and planned
for publication as an ISO International Standard by Spring 1999.
Common IP Security Option (CIPSO)
(I) An Internet Protocol option that was designed by the Trusted
Systems Interoperability Group (TSIG) to carry hierarchic and non-
hierarchic security labels. (Once called "Commercial IP Security
Option"). [CIPSO]
(C) CIPSO enables security attributes to be associated with an IP
datagram. These attributes are used to make security decisions at
the IP layer in the source and destination hosts and in any
trusted gateways along the way.
common name
(I) 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] (Also see: ("subject" and "issuer" in) X.509
public-key certificate.)
(C) For example, "Dr. Albert Einstein", "The United Nations", or
"12-th Floor Laser Printer".
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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.
(C) Usually understood to include cryptographic algorithms and key
management methods and processes, devices that implement them, and
the life cycle management of those keys and devices.
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. (Also see: category.)
(C) The term is usually understood to include the special handling
procedures to be used for the information.
compromise
See: data compromise, security compromise.
compromised key list (CKL)
(O) MISSI usage: A list that identifies keys for which
unauthorized disclosure or alteration may have occurred. (See:
data compromise.)
COMPUSEC
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.
(C) For example, the CERT Coordination Center at Carnegie-Mellon
University (sometimes called "the" CERT) and the Computer Incident
Advisory Capability.
Computer Incident Advisory Capability (CIAC)
(N) A computer emergency response team in the U.S. Department of
Energy.
computer network
(I) A collection of host computers together with the subnetwork or
internetwork through which they can exchange data.
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(C) 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 security (COMPUSEC)
(I) Measures that implement and assure security services in a
computer system, particularly those that assure access control
service.
(C) Usually understood to include functions, features, and
technical characteristics of computer hardware and software,
especially operating systems.
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 elements referred to in standards that
are either selected or defined by separate user communities.
[CSOR] (Also 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.
(C) 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) gov(101)
csor(3)}.
COMSEC
See: communication security.
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. (Also see: administrative security.)
(C) Configuration control helps protect against unauthorized or
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malicious alteration of a system and thus provides assurance of
system integrity. (Also see: malicious logic.)
confinement property
See: (secondary definition in) 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.
(C) A connection-oriented data integrity service would be able to
detect lost or reordered datagrams within a stream of datagrams.
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]
controlled security mode
(C) Internet Standards Process documents SHOULD NOT use this term.
It was defined in an earlier version of the U.S. Department of
Defense policy that regulates system accreditation, but was
subsumed by "partitioned security mode" in the current version.
[DOD2]
(C) The term refers to a mode of operation of an information
system, wherein at least some users with access to the system have
neither a security clearance nor a 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 as they are in "multilevel security
mode".
(C) This mode was intended to provide an alternative to encourage
ingenuity in meeting the security requirements of Defense policy
in manner less restrictive than the dedicated security mode and
the 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.
cookie
(I) access control usage: A synonym for "capability" or "ticket"
in an access control system.
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(I) IPsec usage: Data exchanged by ISAKMP to prevent certain
denial of service attacks at the establishment of a security
association.
(I) HTTP usage: 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.
(C) 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
includes 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.
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. (Also see: GeneralizedTime, UTCTime.)
copy
See: card copy.
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. (Also see: data
integrity, source integrity).
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
reporting it so that corrective action can be taken.
country code
(I) An identifier that is defined for a nation by ISO. [I3166]
(C) For each nation, ISO Standard 3166 defines a unique two-
character alphabetic code, a unique three-character alphabetic
code, and a 3-digit code. Among the many uses of these codes, the
two-character codes are used as top-level domain names.
covert channel
(I) A intra-system communication channel that permits two
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cooperating entities, without exceeding their access
authorizations, to transfer information in a way that violates the
system's security policy.
(O) "A communications channel that allows two cooperating
processes to transfer information in a manner that violates the
system's security policy." [NCS04]
(C) The cooperating entities can be either two insiders or an
insider and an outsider. Of course, an outsider has no access
authorization at all. Covert channels are system features that are
not designed or intended for information transfer. There are two
kinds:
- "Timing channel": 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.
- "Storage channel": A system feature that enables one system
entity to signal information to another entity by directly or
indirectly writing a storage location that is later directly or
indirectly read by the second entity.
CPS
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 to do so. (Also
see: hacker and intruder.)
CRC
See: cyclic redundancy check.
credential, credentials
(I) Data that is transferred or presented to establish either a
claimed identity or the authorizations of a system entity. (Also
see: authentication information.)
(O) "Data that is transferred to establish the claimed identity of
an entity." [I7498 Part 2]
critical
1. (I) "Critical" system resource: A condition of a service or
other system resource such that denial of access to that resource
would jeopardize a system user's ability to perform a primary
function or would result in other serious consequences. (Also see:
availability, sensitive.)
2. (C) "Critical" extension: Each extension of an X.509
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certificate (or CRL) is marked as being either critical or non-
critical. If an extension is critical and a certificate user (or
CRL user) does not recognize the extension type or does not
implement its semantics, then the user is required to treat the
certificate (or CRL) as invalid. If an extension is non-critical,
a user that does not recognize or implement that extension type is
permitted to ignore the extension and process the rest of the
certificate (or CRL).
CRL
See: certificate revocation list.
CRL distribution point
See: distribution point.
CRL extension
See: extension.
cross-certificate
See: cross-certification.
cross-certification
(I) The act or process by which two CAs each certify a public key
of the other, issuing a public-key certificate to that other CA.
(C) Cross-certificates enable two certificate users to validate
each other's certificate, even when the users are certified under
different certification hierarchies.
cryptanalysis
(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.
(Also see: cryptology.)
(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]
(C) The "O" definition states the traditional goal of
cryptanalysis--convert the ciphertext to plaintext (which usually
is cleartext) 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
the "I" definition reflects that. In all cases, however, a
cryptanalyst tries to uncover or reproduce someone else's
sensitive data, such as cleartext, 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.
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crypto
(C) Except as part of certain long-established terms listed in the
glossary, Internet Standards Process documents SHOULD NOT use this
abbreviated term because it may be misunderstood. Instead, use
"cryptography" or "cryptographic".
cryptographic algorithm
(I) An algorithm that employs the science of cryptography,
including encryption algorithms, cryptographic hash algorithms,
digital signature algorithms, and 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. For
example, see: PKCS #11.
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. (Compare with: cryptographic module.)
cryptographic hash
See: (secondary definition in) hash function.
cryptographic ignition key (CIK)
(I) A physical (usually electronic) token used to store,
transport, and protect cryptographic keys. (Sometimes abbreviated
as "crypto ignition key").
(C) A typical use is to divide a split key between a CIK and a
cryptographic module, so that the two must be combined to
regenerate a key-encrypting key and thus activate the module and
other keys it contains.
cryptographic key
(I) Usually shortened to just "key". An input parameter that
varies the transformation performed by a cryptographic algorithm.
(O) "A sequence of symbols that controls the operations of
encipherment and decipherment" [I7498 Part 2]
(C) If a key value must be kept secret, the sequence of symbols
(usually bits) that comprise it should be random, or at least
pseudo-random, because that makes the key hard for an adversary to
guess. (See: cryptanalysis, brute force attack.)
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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
(I) A set of cryptographic algorithms together with the key
management processes that support the use of the algorithms in
some application context.
(C) This definition covers a wider range of algorithms than the
following definition from X.509:
(O) "A collection of transformations from plaintext into
ciphertext 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
(I) A portable, user-controlled, physical device used to store
cryptographic information and possibly perform cryptographic
functions. (Also see: cryptographic card, token.)
(C) A smart token may implement some set of cryptographic
algorithms and may implement related algorithms and key management
functions, such as a random number generator. A smart
cryptographic token may contain a cryptographic module or may not
be explicitly designed that way.
cryptography
(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. (Also see: cryptology. Compare with:
steganography.)
(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]
Cryptoki
See: (secondary definition in) PKCS #11.
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cryptology
(I) The science that includes both cryptography and cryptanalysis,
and sometimes is said to include steganography.
cryptonet
(I) A group of system entities that share a secret cryptographic
key for a symmetric algorithm.
cryptoperiod
(I) The time span during which a particular key is authorized to
be used in a cryptographic system. (Also see: key management.)
(C) 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.
(C) Although we deprecate its prefix, this term is long-
established in COMPUSEC usage. (See: crypto) In the context of
certificates and public keys, "key lifetime" and "validity period"
are often used instead.
cryptosystem
(C) Internet Standards Process documents SHOULD NOT use this term
as an abbreviation for cryptographic system. (For rationale, see:
crypto.)
cut-and-paste attack
(I) An active attack on the data integrity of ciphertext, effected
by replacing sections of ciphertext with other ciphertext, such
that the result appears to decrypt correctly but actually decrypts
to plaintext that is forged to the satisfaction of the attacker.
cyclic redundancy check (CRC)
(I) Sometimes called "cyclic redundancy code". 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.
DAC
See: Data Authentication Code, discretionary access control.
data
(I) Information in a specific physical representation, usually a
sequence of symbols that have meaning; especially a representation
of information that can be processed or produced by a computer.
Data Authentication Algorithm
(N) A keyed hash function equivalent to DES cipher block chaining
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with IV = 0 [A9009].
(C) Internet Standards Process documents SHOULD NOT use this term
in an uncapitalized form as a general synonym for other kinds of
checksums.
data authentication code vs. Data Authentication Code (DAC)
1. (N) Capitalized: "The Data Authentication Code" refers to a
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]).
2. (C) Not capitalized: Internet Standards Process documents
SHOULD NOT use "data authentication code", because this 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.
(C) Internet Standards Process documents SHOULD NOT use this term
in an uncapitalized form as a general synonym for other kinds of
checksums.
data compromise
(I) A security violation in which information is exposed to
potential unauthorized access, such that unauthorized disclosure,
alteration, or use of the information may have occurred. (See:
compromise.)
data confidentiality
(I) "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]. (Also
see: data confidentiality service.)
(C) Internet Standards Process documents SHOULD NOT use this term
as a synonym for "privacy", which is a different concept.
data confidentiality service
(I) A security service that protects data against unauthorized
disclosure. (Also see: data confidentiality).
(C) Internet Standards Process documents SHOULD NOT use this term
as a synonym for "privacy", which is a different concept.
Data Encryption Algorithm (DEA)
(N) A symmetric (see: symmetric cryptography) block cipher that
uses a 64-bit key, of which 56 bits are independently chosen and 8
are parity bits. It maps a 64-bit block into another 64-bit block.
[FP046]
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(C) This algorithm is usually referred to as "DES". (See: Data
Encryption Standard.) 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.
(Also see: key-encrypting key.)
Data Encryption Standard (DES)
(N) A U.S. Government standard [FP046] that specifies the Data
Encryption Algorithm and states policy for using the algorithm to
protect unclassified, sensitive data. (Also see: AES.)
data integrity
(I) The property that data has not been changed, destroyed, or
lost in an unauthorized or accidental manner.
(O) "The property that information has not been modified or
destroyed in an unauthorized manner." [I7498 Part 2]
(C) Deals with constancy of and confidence in data values, not
with the information that the values represent (see: correctness
integrity) or the trustworthiness of the source of the values
(see: source integrity).
data integrity service
(I) A security service that protects against unauthorized changes
to data, including both intentional change or destruction and
accidental change or loss, by ensuring that changes to data are
detectable. (Also see: data integrity.)
(C) 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.
(C) 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.
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data origin authentication
(I) "The corroboration that the source of data received is as
claimed." [I7498 Part 2] (Also 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.
(Also see: authentication, authentication service.)
(C) 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.
(C) A digital signature mechanism can be used to provide this
service, because an adversary, who does not know the private key
of the signer, cannot forge the correct signature. However, by
using the signer's public key, anyone can verify the origin of
correctly signed data.
(C) This service is usually bundled with connectionless data
integrity service. (See: "relationship between data integrity
service and authentication services" under data integrity service.
data privacy
(C) Internet Standards Process documents SHOULD NOT use this term
because it mix concepts in a potentially misleading way. Instead,
use "data confidentiality" or "privacy", depending on what is
meant.
data security
(I) The protection of data from disclosure, alteration,
destruction, or loss that either is accidental or is intentional
but unauthorized.
(C) Both data confidentiality service and data integrity service
are needed to achieve data security.
DEA
See: Data Encryption Algorithm.
deception
See: (secondary definition in) threat consequence.
decipher
(C) Internet Standards Process documents SHOULD NOT use this term
as a synonym for "decrypt". However, see the usage note under
"encryption".
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decipherment
(C) Internet Standards Process documents SHOULD NOT use this term
as a synonym for "decryption", except in special circumstances.
(See: (usage discussion under) encryption.)
decode
(I) Convert encoded data back to its original form of
representation. (Compare with: decrypt.)
(C) Internet Standards Process documents SHOULD NOT use this term
as a synonym for "decrypt", because that would mix concepts in a
potentially misleading way.
decrypt
(I) Cryptographically restore ciphertext to the plaintext form it
had before encryption.
decryption
See: (secondary definition in) 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 single classification level or category of
information or a range of levels and categories.
(C) This mode is defined formally in U.S. Department of Defense
policy regarding system accreditation [DOD2], but the term is also
used outside the Defense Department and outside the Government.
degauss
(I) Apply a magnetic field to permanently remove, erase, or clear
data from a magnetic storage medium, such as a tape or disk.
[NCS25]
DEK
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.
denial of service
(I) The prevention of authorized access to a system resource or
the delaying of system operations and functions. (Also see:
availability, critical (resource of a system).)
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DES
See: Data Encryption Standard.
dictionary attack
(I) An attack that uses a brute-force approach of successively
trying all the words in some large, exhaustive list.
(C) For example, an attack on an authentication service by trying
all possible passwords; or 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].
(C) 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.
(C) The difficulty of breaking Diffie-Hellman is considered to be
equal to the difficulty of computing discrete logarithms modulo a
large prime. 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.
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 set (a
data object used by a computer) to which is appended a computed
digital signature value that depends on the data set. (Also see:
attribute certificate, public-key certificate.)
(C) Internet Standards Process documents SHOULD NOT use this term
to refer to a signed CRL or CKL. Although the recommended
definition can be interpreted to include those items, the security
community does not use the term with those meanings.
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digital certification
(C) Internet Standards Process documents SHOULD NOT use this term
as a synonym for "certification", 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 set that represents the information
originally written in a document in a different medium (usually
paper) or is an analogue of documents of that type.
digital envelope
(I) A digital envelope for a recipient is a combination of (a)
encrypted content data (of any kind) and (b) the content
encryption key in an encrypted form that has been prepared for the
use of the recipient.
(C) In Internet Standards Process documents, this 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 yet widely-
established.
(C) 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 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)
(C) Internet Standards Process documents SHOULD NOT use this term
as a synonym for "digital certificate" because (a) it is the
service mark of commercial firm, (b) it unnecessarily duplicates
the meaning of other, well-established terms, and (c) a
certificate is not always used as authentication information. In
some contexts, however, it may be useful to explain that the key
conveyed in a public-key certificate can be used to verify an
identity and thus the certificate can be thought of as digital
identification information. (See: identification information.)
digital key
(C) The adjective "digital" need not be used with "key" or
"cryptographic key", unless the context is insufficient to
distinguish the key from another kind of key, such as a metal key
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for a door lock.
digital notary
(I) Analogous to a notary public; provides a trusted date-and-time
stamp for a document that proves the document existed at a point
in time, and may also verify the signatures on a signed document.
(Also see: notarization.)
digital signature
(I) A value computed with a cryptographic algorithm and appended
to a data set in such a way that any recipient of the data can use
the signature to verify the data's origin and integrity. (Also
see: data origin authentication service, data integrity service.)
(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]
(C) Typically, the data set 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 set. The signature value is a
protected checksum, because the properties of a cryptographic hash
ensure that if the data set 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
signatory.
(C) Some digital signature schemes use an asymmetric encryption
algorithms (e.g., see: RSA) to transform the hash result. Thus,
when Alice needs to sign a message to send to Bob, she can encrypt
the hash result using her private key. Bob receives both the
message and the digital signature. Bob decrypts the signature
using Alice's public key and compares 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.
(C) 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
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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 that produces 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:
Digital Signature Standard.)
Digital Signature Standard (DSS)
(N) The U.S. Government standard [FP186] that specifies the
Digital Signature Algorithm (DSA), which involves asymmetric
cryptography.
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.
(C) 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
performing other functions to protect intellectual property
rights. [ACM]
directory, Directory
(I) When not capitalized, directory 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.
When capitalized, Directory refers specifically to the X.500
Directory.
Directory Access Protocol (DAP)
(N) An OSI protocol [X519] for communication between a Directory
User Agent (a client) and a Directory System Agent (a server).
(Also see: Lightweight Directory Access Protocol.)
disaster plan
(I) A synonym for "contingency plan.
disclosure (i.e., unauthorized disclosure)
See: (secondary definition in) threat consequence.
discretionary access control (DAC)
(I) An access control service that enforces a security policy
based on the identity of system entities and their authorizations
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to access system resources. (Also see: access control list,
identity-based security policy, mandatory access control.)
(C) This service is termed "discretionary" because an entity might
have access rights that permit the entity, by its own volition, to
enable another entity to access some resource.
(O) "A means of restricting access to objects 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]
disruption
See: (secondary definition in) threat consequence.
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].
(C) Since there is more than one way to encode ASN.1 in BER, 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)
(I) An identifier that uniquely represents an object in the X.500
Directory Information Tree (DIT) [X501]. (Also see: domain name.)
(C) 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.
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.
(C) 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. A CRL obtained from a
distribution point may cover either all reasons for which a
certificate might be revoked or only some of that reasons, may be
issued by either the authority that signed the certificate or some
other authority, and may contain revocation entries for only a
subset of the full set of certificates issued by one CA or may
contain revocation entries for multiple CAs.
DN
See: distinguished name.
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DNS
See: Domain Name System.
domain
(I) General security usage: The set of system resources that a
system entity (or set of system entities, perhaps defined by a
security architecture or security policy) has the ability to
access. (Also see: security perimeter.)
(I) Internet usage: That part of the Internet domain name space
tree [R1034] that is at or below the name the 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. (Also see: Domain Name System.)
(I) IPsec usage: An IPsec ISAKMP domain of interpretation (DOI)
defines payload formats, exchange types, and conventions for
naming security-relevant information such as security policies or
cryptographic algorithms and modes. (The DOI concept is based on
work by the TSIG CIPSO Working Group.)
(O) MISSI usage: The domain of a MISSI certification authority is
the set of MISSI users whose certificates are signed by the
authority.
(O) OSI usage: An administrative partition of a complex
distributed OSI system.
domain name
(I) The style of identifier--a sequence of case-insensitive ASCII
labels separated by dots ("bbn.com.")--defined for subtrees in the
Internet Domain Name System [R1034] and used in other Internet
identifiers, such as host names ("rosslyn.bbn.com."), mailbox
names ("rshirey@bbn.com."), and URLs
("http://www.rosslyn.bbn.com/foo"). (Also see: domain and
distinguished name.)
(C) The domain name space of the DNS 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). The root's label is the null
string, so a complete domain name ends in a dot. The top-level
domains, those immediately below the root, include COM, EDU, GOV,
INT, MIL, NET, ORG, and two-letter country codes (such as US) from
ISO-3166. [R1591]
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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 (for example, "rosslyn.bbn.com" is "192.1.7.10") and
locating a host that accepts mail for some mailbox address.
[R1034]
(C) The DNS has three major components:
- Domain name space and resource records: Specifications for the
tree-structured domain name space, and data associated with the
names.
- 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.
- Resolvers: Programs that extract information from name servers
in response to client requests; typically, system routines
directly accessible to user programs.
(C) Extensions to the DNS [R2065] 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, and (c) data origin authentication service for
transactions between resolvers and servers.
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.
dongle
(I) A portable, physical, electronic device that is required to be
attached to a computer to enable a particular software program to
run. (Also see: token.)
(C) A dongle is essentially a physical key used for copy
protection of software, because the program will not run unless a
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 to be connected to a serial I/O
port of a personal computer.
downgrade
(I) Reduce the classification level of information in an
authorized manner.
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draft RFC
(C) Internet Standards Process documents SHOULD NOT use this term,
because the Request for Comment series is archival in nature and
does not have a "draft" category. Instead, use "Internet Draft".
DSA
See: Digital Signature Algorithm.
DSS
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. (Also see:
no-lone zone, separation of duties, split knowledge.)
dual signature
(O) SET usage: A single digital signature that protects two
separate messages by including the hash results for both sets in a
single encrypted value. [SET2]
(C) 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 allow verification of data
integrity without complete disclosure of the data.
EAP
See: Extensible Authentication Protocol
eavesdropping
(I) Passive wiretapping done secretly, i.e., without the knowledge
of the originator or the intended recipients of the communication.
ECB
See: electronic codebook.
EDI
See: electronic data interchange.
EDIFACT
See: (secondary definition in) electronic data interchange.
EE
(C) Internet Standards Process documents SHOULD NOT use this
acronym because of possible confusion among "end entity", "end-to-
end encryption", "escrowed encryption standard", and other terms.
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EES
See: Escrowed Encryption Standard.
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)
(I) 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 ciphertext [FP081].
electronic commerce
(I) General usage: 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.
(O) SET usage: "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.
(C) EDI formats have been standardized primarily by ANSI X12 and
by EDIFACT (EDI for Administration, Commerce, and Transportation),
an international, UN-sponsored standard primarily used in Europe
and Asia. These two are aligning to create a single global EDI
standard.
elliptic curve cryptography (ECC)
(I) A type of asymmetric cryptography based on mathematics of
groups defined by the points on a curve.
(C) 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. ECC is based on the mathematics of
groups defined by the points on a curve, where the curve is
defined by a quadratic equation in a finite field. ECC can be used
to define an algorithm for key agreement that is an analog of
Diffie-Hellman and an algorithm for digital signature that is an
analog of DSA.
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emanation
(I) An signal (electromagnetic, acoustical, or other byproduct)
that is emitted by a system (through radiation or conductance) as
a consequence of its operation, and that may contain information.
(Also see: TEMPEST.)
emanations security (EMSEC)
(I) Physical constraints to prevent information compromise through
signals emanated by a system, particular the application of
TEMPEST technology to block electromagnetic radiation.
emergency plan
(I) A synonym for "contingency plan".
EMSEC
See: emanations security.
EMV
(I) An acronym for "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 IPsec protocol [R2406] designed to provide a mix
of security services--especially data confidentiality service--in
the Internet Protocol. (Also see: Authentication Header.)
(C) ESP may be used alone, or in combination with the IPsec AH
protocol, 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 inserted after the IP header and before
either the upper layer protocol header (transport mode) or an
encapsulated 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
(C) Internet Standards Process documents SHOULD NOT use this term
as a synonym for "encrypt". However, see the usage note under
"encryption".
encipherment
(C) Internet Standards Process documents SHOULD NOT use this term
as a synonym for "encryption", except in special circumstances
that are explained in the usage discussion under "encryption".
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encode
(I) Use a system of symbols to represent information, which might
originally have some other representation. (Also see: decode.)
(C) Examples include Morse code, ASCII, and BER. Internet
Standards Process documents SHOULD NOT use this term as a synonym
for "encrypt", because encoding is not usually intended to conceal
meaning.
encrypt
(I) Cryptographically transform data to produce ciphertext. (See:
encryption.)
encryption
(I) The cryptographic transformation of data (called "plaintext")
into a form (called "ciphertext") that conceals the data's
original meaning to prevent it from being known or used. If the
transformation is reversible, then corresponding reversal process
is called "decryption", which is a transformation that restores
encrypted data to its original state. (Also see: cryptography.)
(C) Usage note: For this concept, Internet Standards Process
documents should use the verb "to encrypt" (and related
variations: encryption, decrypt, and decryption). Because of
cultural biases, however, some international usage, particularly
ISO and CCITT standards, avoid "to encrypt" and instead use the
verb "to encipher" (and related variations: encipherment,
decipher, decipherment).
(O) "The cryptographic transformation of data (see: cryptography)
to produce ciphertext." [I7498 Part 2]
(C) Usually, the plaintext input to an encryption operation is
cleartext. But in some cases, the plaintext may be ciphertext that
was output from another encryption operation. (Also see:
superencryption.)
(C) 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 value that varies the transformation and, in some cases, (b)
an initialization value 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 encrypting data, rather than for verifying
digital signatures or performing other cryptographic functions.
C) A v3 X.509 public-key certificate may have a "keyUsage"
extension which indicates the purpose for which the certified
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public key is intended.
end entity
(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 a purpose or purposes other than
signing a digital certificate; i.e., an entity that is not a CA.
(O) "A certificate subject which uses its public [sic] key for
purposes other than signing certificates." [X509]
(C) Internet Standards Process documents SHOULD NOT use the X.509
definition, because it is misleading and incomplete. First, the
X.509 definition should say "private key" rather than "public key"
because certificates are not usefully signed with a public key.
Second, the X.509 definition is weak 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".
(C) 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 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.
(C) Whether a subject can play both CA and non-CA roles, with
either the same or different certificates, is a matter of policy.
(See: certification practice statement.) 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".
end system
(I) An OSI term for a computer that implements all seven layers of
the OSIRM and may attach to a subnetwork. (In the context of the
Internet Protocol Suite, usually called a "host".)
end-to-end encryption
(I) Continuous protection of data that flows between two points in
a network, provided 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 destination. (Also see: link encryption,
wiretapping.)
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(C) 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
(I) In a PKI or other application of asymmetric cryptography, a
synonym for "end entity". But the term "end entity" is preferred.
entity
See: system entity.
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]
ephemeral key
(I) A public key or a private key that is relatively short-lived.
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 encrypted
telecommunications when interception is lawfully authorized.
(C) Both SKIPJACK and the LEAF are to be implemented in equipment
used to encrypt and decrypt unclassified, sensitive
telecommunications data.
ESP
See: Encapsulating Security Payload.
Estelle
(N) A language (ISO 9074-1989) for formal specification of
computer network protocols.
evaluated system
(I) Refers to a system that has been evaluated against security
criteria such as the Trusted Computer System Evaluation Criteria,
or the Common Criteria for Information Technology Security
Evaluation.
expire
See: certificate expiration.
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exposure
See: (threat action definition in) threat consequence.
Extensible Authentication Protocol
(I) A framework that supports multiple, optional authentication
mechanisms for PPP, including cleartext passwords, challenge-
response, and arbitrary dialog sequences. [R2284]
(C) This protocol is intended for use primarily by a host or
router that connects to a PPP network server via switched circuits
or dial-up lines.
extension
(I) A data item defined for optional inclusion in a v3 X.509
public-key certificate or a v2 X.509 CRL.
(C) 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. (Also see: PKIX private extension, SET private
extensions.)
extranet
(I) A computer network that an organization uses to carry
application data traffic between the organization and its business
partners. (Also see: Intranet.)
(C) An extranet can be implemented securely, either on the
Internet or using Internet technology, by constructing it as a
virtual private network.
failure control
(I) A methodology used to provide fail-safe or fail-soft
termination and recovery of functions and processes when failures
are detected or occur in a system. [FP039]
fail safe
(I) A mode of system termination that automatically leaves system
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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
the system.
Federal Information Processing Standards (FIPS)
(N) The Federal Information Processing Standards Publication (FIPS
PUB) series issued by the U.S. National Institute of Standards and
Technology as technical guidelines for U.S. Government
procurements of information processing system equipment and
services. [FIPS 39, FP046, FP081, FP140, FP180, FP186, FP185,
FP188]
(C) 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)
(N) A PKI being planned to establish facilities, specifications,
and policies needed by the U.S. Federal Government to use public-
key certificates for INFOSEC, COMSEC, and electronic commerce
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 obsolete document defining emanation, anti-tamper, security
fault analysis, and manual key management criteria for DES
encryption devices, primary for OSI layer 2. Renamed "FIPS PUB
140" when responsibility for protecting unclassified, sensitive
information was transferred from NSA to NIST, and then replaced by
FIPS PUB 140-1.
File Transfer Protocol (FTP)
(I) A TCP-based, application-level, Internet Standard protocol for
moving data files from one computer to another. [R0959]
filtering router
(I) An internetwork router that selectively prevents the passage
of data packets according to a security policy.
(C) A filtering router may be used as a firewall or part of a
firewall. 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.
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The rules mostly involve values of data packet control fields
(especially IP source and destination addresses and TCP port
numbers).
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
(I) A pattern of curves formed by the ridges on a fingertip. (Also
see: biometric authentication, thumbprint.)
(C) Internet Standards Process documents SHOULD NOT use this term
as a synonym for "hash result" because it mixes concepts in a
potentially misleading way.
(C) Internet Standards Process documents SHOULD NOT use this term
in the following PGP sense, because it mixes concepts in a
potentially misleading way and duplicates the meaning of "hash
result":
(C) PGP usage: A hash result used to authenticate a public key
(key fingerprint) or other data. [PGP]
FIPS
See: Federal Information Processing Standards.
FIPS PUB 140-1
(N) A 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. (To be
superseded by the Common Criteria. Also see: Federal Information
Processing Standards.)
(C) 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.
firewall
(I) An internetwork gateway that restricts data communication
traffic to and from a computer network to protect that network's
system resources against threats from other networks that are
outside the firewall. (Also see: guard.)
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(C) A firewall typically separates a smaller, secure network (such
as a corporate LAN) from a larger network (such as the Internet).
Installed at the point where the networks connect, the firewall
applies security policy rules to control traffic that flows in and
out of the protected network.
(C) 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 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 or programmable read-only memory) such that the
programs and data cannot be dynamically written or modified during
execution of the programs. (Compare with: hardware, software.)
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]
flooding
(I) An attack that attempts to cause a failure in (especially, in
the security of) a computer system or other data processing entity
by providing more input than the entity can process properly.
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 the U.S. National Security Agency
(NSA), used for a family of interoperable security products that
implement a NIST/NSA-approved suite of cryptographic algorithms
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for digital signature, hash, encryption, and key exchange. The
products include a PC card that contains a CAPSTONE chip, serial
port modems, server boards, smart cards, and software
implementations.
forward secrecy
See: public-key forward secrecy.
FPKI
See: Federal Public-Key Infrastructure.
FTP
See: File Transfer Protocol.
gateway
(I) A relay mechanism that attaches to two (or more) computer
networks that have similar functions but dissimilar
implementations and that enables host computers on one network to
communicate with hosts on the other; an intermediate system that
is the interface between two computer networks. (Also see: bridge,
firewall, guard, internetwork, proxy server, router, and
subnetwork.)
(C) Gateways are conceivable at any OSI layer, but actual gateways
operate at OSI layer 3 (see: bridge, router) or OSI layer 7 (see:
proxy server). When the two networks differ in the protocol by
which they offer service to hosts, the gateway may translate one
protocol into another or otherwise facilitate interoperation of
hosts (see: Internet Protocol).
GCA
See: geopolitical certificate authority.
GeneralizedTime
(N) The ASN.1 data type "GeneralizedTime" (specified in 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. (Also see: Coordinated Universal
Time, UTCTime.)
Generic Security Service Application Program Interface (GSS-API)
(I) An Internet Standard protocol [R1508] 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.
(C) "A GSS-API caller accepts tokens provided to it by its local
GSS-API implementation and transfers the tokens to a peer on a
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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]." [R1508]
geopolitical certificate authority (GCA)
(O) SET usage: In a SET certification hierarchy, an optional level
that is certified by a brand certification authority 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.
Green Book
(C) Except as an explanatory appositive, Internet Standards
Process documents SHOULD NOT use this term as a synonym for
"Defense Password Management Guideline" [CSC2]. Instead, use the
full proper name of the document or, in subsequent references, a
conventional abbreviation. (See: Rainbow Series.)
(C) Usage note: To improve international comprehensibility of
Internet Standards and the Internet Standards Process [R2026],
Internet Standards Process documents SHOULD NOT use "cute"
synonyms for document titles. No matter how popular and clearly
understood a nickname may be in one community, it is likely to
cause confusion in others. For example, in addition to the meaning
given above, there are several other information system standards
called "the Green Book. The following are just a few examples:
- Any 1992 standard issued by the ITU-T (then CCITT).
- "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.
GSS-API
See: Generic Security Service Application Program Interface.
guard
(I) A gateway that is interposed between two networks (or
computers, or other information systems) operating at different
security levels (one is usually higher than the other) and is
trusted to mediate all information transfers between the two
levels, to either ensure that no sensitive information from the
first (higher) level can leak to the second (lower) level, or to
protect against destruction of data on the first (higher) level.
(Also see: firewall.)
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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 support the integrity and
confidentiality of application data.
hacker
(I) Someone with a strong interest in computers, who enjoys
learning about them and experimenting with them. (Also see:
cracker.)
(C) The recommended definition is the original meaning of the term
(circa 1960), which then had a neutral or positive connotation.
Today, the term is frequently misused, especially by journalists,
to have the pejorative meaning of cracker.
handle
(I) Perform processing operations on data, such as receive and
transmit, collect and disseminate, create and delete, store and
retrieve, read and write, and compare.
hardware
(I) The physical, material components of a computer system.
(Compare with: firmware, software.)
hardware token
See: token.
(O) SET usage: "A portable device (for example, smart card, and
PCMCIA cards) specifically designed to store cryptographic
information and possibly perform cryptographic functions in a
secure manner." [SET2]
hash function
(I) An algorithm that computes a value based on a data set (such
as a message or file; usually variable-length; possibly very
large), thereby mapping the data set to a smaller data object
(called the hash result) which is usually a fixed-size value.
(Also see: checksum, keyed hash.)
(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]
(C) The kind of hash function needed for security applications is
a one-way function called a cryptographic hash function, an
algorithm for which it is computationally infeasible (because no
attack is significantly more efficient than brute force) to find
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either (a) a data set that maps to a pre-specified hash result
(the "one-way" property) or (b) two data sets that map to the same
hash result (the "collision-free" property). (Also see: MD2, MD4,
MD5, SHA-1.)
(C) A cryptographic hash is "good" in the sense stated above by
X.509. Any change to an input data set will, with high
probability, result in a different hash result, so that the result
of a cryptographic hash makes a good checksum for a data set.
hash result
(I) The output of a hash function.
(O) "The output produced by a hash function upon processing a
message" (where "message" is broadly defined as "a digital
representation of data"). [ABA] (The recommended definition is
compatible with this ABA definition, but we avoid the unusual
definition of "message".)
hash value
(C) Internet Standards Process documents SHOULD NOT use this term
as a synonym for "hash result" (the output of a hash function)
because it might be confused with "hashed" value (the input to a
hash function).
hierarchical PKI
(I) A PKI architecture based on a certification hierarchy. (Also
see: 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.
hierarchy of trust
(C) Internet Standards Process documents SHOULD NOT use this term
as a synonym for "certification hierarchy" because it mixes
concepts in a potentially misleading way and duplicates the
meaning of another, standardized term. (Also see: trust, web of
trust.)
hijack attack
(I) A form of active wiretapping in which the attacker seizes
control of a previously established communication association.
(Also see: man-in-the-middle attack, piggyback attack.)
HMAC
(I) A keyed hash [R2104] that can be based on any interactive
cryptographic hash (e.g., MD5 or SHA-1), so that the cryptographic
strength of HMAC depends on the properties of the selected
cryptographic hash.
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(C) Assume that H is a generic cryptographic hash in which a basic
compression function is interated 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)).
(C) The goals of HMAC are as follows:
- To use available cryptographic hash functions without
modification, particularly those 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
(I) 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. (Also see: entrapment.)
host
(I) 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. (Compare with: end
system.) In the context of the Internet protocol suite, a term for
a networked computer that does not forward Internet Protocol
packets that are not addressed to the computer itself. (Compare
with: router.)
(C) Derivation: As viewed by its users, a host "entertains"
guests, providing application layer services or access to other
computers attached to the network. Although some traditional
peripheral service devices, such as printers, can now be
independently connected to networks, they are not usually called
hosts.
HTML
See: Hypertext Markup Language.
HTTP
See: Hypertext Transfer Protocol.
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https
(I) When used in the first part of a URL (the part that precedes
the colon and that specifies an access scheme or protocol), this
term specifies the use of HTTP enhanced by a security mechanism,
normally SSL. (Compare with: S-HTTP.)
hybrid encryption
(I) An application of cryptography that combines two or more
encryption algorithms, particularly a combination of symmetric and
asymmetric encryption (e.g., see: digital envelope).
(C) Asymmetric algorithms require more computation than
equivalently strong symmetric ones. Thus, asymmetric encryption is
not normally used for data confidentiality except in distributing
symmetric keys in applications where the key data is usually short
(in terms of bits) compared to the data it protects. For example,
see: MSP, PEM, PGP.
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 (such as by selecting the object with a mouse
pointer and clicking).
hypermedia
(I) A generalization of hypertext; any media that contain
hyperlinks, which point to additional 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 Hypertext Markup
Language and accessed using a web browser. (Also see: hypermedia.)
Hypertext Markup Language (HTML)
(I) A platform-independent system of syntax and semantics 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. [R1866]
Hypertext Transfer Protocol (HTTP)
(I) An Internet application-level, client-server protocol used to
carry data requests and responses in the World Wide Web [R2068].
(Also see: hypertext.)
IAB
See: Internet Architecture Board.
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ICMP flood
(I) A denial of service attack that sends a host more Internet
Control Message Protocol echo request ("ping") packets than the
protocol implementation can handle. (Also see: flooding.)
ICRL
See: indirect certificate revocation list.
IDEA
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. (Also see: authentication.)
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]
(Also see: rule-based security policy.)
IEEE
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,
developing a comprehensive reference standard for asymmetric
cryptography; covering discrete logarithm (e.g., DSA), elliptic
curve, and integer factorization (e.g., RSA); and covering key
agreement, digital signature, and encryption.
IESG
See: Internet Engineering Steering Group.
IETF
See: Internet Engineering Task Force.
IKE
See: IPsec Key Exchange.
in the clear
(I) Not encrypted. (Also see: cleartext.)
indirect certificate revocation list (ICRL)
(I) In X.509, a CRL that may contain certificate revocation
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notifications for certificates issued by CAs other than the issuer
of the list.
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.
(C) Under certain conditions, this notion is equivalent to
semantic security.
information
(I) Facts and ideas, which can be represented (encoded) as various
forms of data.
Information Technology Security Evaluation Criteria (ITSEC)
(N) Standard developed for use in the European Union; accommodates
a wider range of security assurance and functionality combinations
than the TCSEC. To be superseded by the Common Criteria.
INFOSEC
(I) Abbreviation for "information security", referring to security
measures that implement and assure security services in computer
systems (i.e., COMPUSEC) and communication systems (i.e., COMSEC).
initialization value (IV)
(I) An input parameter that sets the starting state of a
cryptographic algorithm or mode. (Sometimes called "initialization
vector" or "message indicator".) For example, cipher block
chaining mode requires an IV.
(C) An IV can be used to introduce cryptographic variance in
addition to that provided by a key (see: salt), and to synchronize
one cryptographic process with another.
initialization vector
(I) A synonym "for initialization value".
insider attack
See: (secondary definition in) attack.
Institute of Electrical and Electronics Engineers, Inc. (IEEE)
(N) The IEEE is a not-for-profit association of more than 330,000
individual members in 150 countries. The IEEE produces 30 percent
of the world's published literature in electrical engineering,
computers, and control technology; holds annually more than 300
major conferences; and has more than 800 active standards with 700
under development. (Also see: Standards for Interoperable LAN/MAN
Security.)
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integrity
See: data integrity, correctness integrity, source integrity,
system integrity.
integrity check
(C) Internet Standards Process documents SHOULD NOT use this term
as a synonym for "cryptographic hash" or "protected checksum",
because it unnecessarily duplicates the meaning of other, well-
established terms.
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.
(Also see: threat.)
International Data Encryption Algorithm (IDEA)
(N) A patented, symmetric (see: symmetric cryptography) block
cipher that uses a 128-bit key and operates on 64-bit blocks.
[Schn]
International Standard
See: (secondary definition in) ISO.
International Traffic in Arms Regulations (ITAR)
(N) 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. (Also see: Wassenaar Arrangement.)
internet vs. 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 and the name and
address spaces that are specified by the IAB [R2026].
(C) The suite is called the "Internet Protocol Suite" (IPS), but
also is popularly know as "TCP/IP", because TCP and IP are two of
its fundamental protocols. The IPS makes it possible for users of
any one of the networks in the Internet to communicate with, or
use the services located on, any of the other networks.
(C) The IPS does not have an Internet Standard that defines a
layered reference model like the OSIRM. However, Internet
community documents refer (inconsistently) to these seven layers:
application, socket, transport, internetwork, network, data link,
and physical. In this Glossary, Internet layers are referred to by
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name to avoid confusing them with OSIRM layers, which are referred
to by number.
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
by the IETF nominating committee. [R2026]
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",
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]
Internet Protocol (IP)
(I) A TCP/IP protocol 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. (Includes both version 4
[R0791] and version 6 [R2460].) (Also see: IP address.)
(C) In the OSIRM, IP would be placed at the top of the layer 3.
Internet Protocol security (IPsec)
(I) (1.) The name of the IETF working group that is specifying a
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security architecture [R2401] and protocols to provide security
services for Internet Protocol traffic. (Implementation is
optional for IP version 4, mandatory for version 6.) (2.) A
collective name for that architecture and set of protocols.
(C) Note that the "s" is lower case.
(C) The IPsec architecture 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. The set of security services 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.
Internet Protocol Suite
See: (secondary definition in) Internet.
Internet Security Association and Key Management Protocol (ISAKMP)
(I) An Internet IPsec protocol 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.
(C) 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 must be provided on ISAKMP exchanges, and a digital
signature algorithm based on asymmetric cryptography must be used
within ISAKMP's authentication component.
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
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Internet. [R2026] (Also see: RFC)
(C) 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 Internet
Protocol Suite. (See: (secondary definition in) Internet). The
"Internet Standards Track" has three levels of increasing
maturity: Proposed Standard, Draft Standard, and Standard.
(Compare with: (levels in) ISO.)
internetwork
(I) A system of interconnected networks; a network of networks.
Usually shortened to "internet". (Also see: internet vs.
Internet.)
(C) An internet is usually built using OSI layer 3 gateways to
connect a set of subnetworks. When the subnetworks differ in the
OSI 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.
(Also 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. (Also
see: 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. (Also
see: cracker.)
intrusion
See: security intrusion.
intrusion detection
(I) A security service that monitors and analyzes system events
for the purpose of noticing, and providing real-time or near real-
time warning of, attempts to access system resources in an
unauthorized manner.
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].
(C) This date may be earlier than the revocation date in the CRL
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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 some
time in the past.
IP
See: Internet Protocol.
IP address
(I) The (internetwork) address assigned to a networked computer
for use by the Internet Protocol.
(C) An IP version 4 [R0791] address 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. For IP version 6
[R2373], the preferred form is x:x:x:x:x:x:x:x, where the "x"s are
the hexadecimal values of the eight 16-bit parts of the address.
For example, FEDC:BA98:7654:3210:FEDC:BA98:7654:3210 and
1080:0:0:0:8:800:200C:417A.
IPRA
(I) Internet PCA Registration Authority. An X.509-compliant CA
that is the top CA of the Internet certification hierarchy
operated by the Internet Society [R1422].
IPsec
See: Internet Protocol security.
IPsec Key Exchange (IKE)
(I) An Internet, IPsec, key-establishment protocol [R2409] (partly
based on OAKLEY) that is intended for obtaining authenticated
keying material for use with ISAKMP and for other security
associations, such as in AH and ESP.
ISAKMP
See: Internet Security Association and Key Management Protocol.
ISO
(I) International Organization for Standardization, a voluntary,
non-treaty organization with voting members that are designated
standards bodies of participating nations and non-voting observer
organizations. (Also see: ANSI, ITU-T.)
(C) ISO and the IEC (the International Electrotechnical
Commission) form the specialized system for worldwide
standardization. (ISO is a class D member of ITU-T.) 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. (ANSI is the U.S.
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voting member of ISO.) Other international organizations,
governmental and non-governmental, in liaison with ISO and IEC,
also take part. In information technology, ISO and IEC have a
joint technical committee, ISO/IEC JTC 1.
(C) 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). 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. (Compare with: (levels in)
Internet Standard.)
ISOC
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). (Also see: certificate creation.)
(C) 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) "Issuer" of a certificate or CRL: The CA that signs a
digital certificate or CRL.
(C) An X.509 certificate always includes the issuer's name. The
name may include a common name value.
2. (N) "Issuer" of a payment card: SET usage: "The financial
institution or its agent that issues the unique primary account
number to the cardholder for the payment card brand." [SET2]
(C) 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
See: International Traffic in Arms Regulations.
ITSEC
See: Information Technology System Evaluation Criteria.
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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". (Also see: X.400, X.500.)
(C) 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 and ISO name and number.
IV
See: initialization value.
KDC
See: Key Distribution Center.
KEA
See: Key Exchange Algorithm.
KEK
See: key-encrypting key.
Kerberos
(N) A system developed at the Massachusetts Institute of
Technology that depends on passwords and symmetric cryptography
(DES) to implement a ticket-based, peer entity authentication
service and access control service distributed in a client-server
network environment. [R1510, Stei]
(C) Kerberos was developed by Project Athena and is named for the
three-headed dog guarding Hades.
key
See: cryptographic key.
key agreement (algorithm or protocol)
(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), can each compute the same value, i.e., each independently
generate the same secret key, that becomes known to both of them
but cannot be computed by other entities. (Compare with: key
transport. Also see: Diffie-Hellman, Key Exchange Algorithm.)
(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]
(O) "The procedure whereby two different parties generate shared
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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 can predetermine the value of the
key." [A9042]
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 center
(I) A centralized key distribution process (used in symmetric
cryptography), usually a separate computer system, that uses key-
encrypting keys (master keys) to encrypt and distribute session
keys needed in a community of users.
(C) An ANSI standard [A9017] defines two types of key center: key
distribution center and key translation center.
key confirmation
(N) "The assurance of the legitimate participants in a key
establishment protocol that the intended parties sharing 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. (Also see: key management.)
key distribution center (KDC)
(I) A type of key center (used in symmetric cryptography) that
implements a key distribution protocol to provide keys (usually,
session keys) to two (or more) entities that wish to communicate
securely. (Also see: key translation center.)
(C) 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 sends that
encrypted set to Alice for her to forward to Bob, or sends it
directly to Bob (although the latter option is not supported in
the ANSI standard [A9017]).
key-encrypting key (KEK)
(I) A cryptographic key that is used to encrypt other keys, either
DEKs or other KEKs, but usually is not used to encrypt application
data.
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key escrow
(I) A system for storing knowledge of a cryptographic key in the
custody of one or more third parties so that the key can be
recovered and used in specified circumstances.
(C) Key escrow can be implemented with various techniques,
including split knowledge. For example, the Escrowed Encryption
Standard 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)
(I) A process that combines the key generation and key
distribution steps needed to set up or install a secure
communication association. (Also see: key agreement, key
transport.)
(O) "The procedure to share a symmetric key among different
parties by either key agreement or key transport." [A9042]
(C) Key establishment involves either key agreement or key
transport. In key transport, one entity does the key generation
and then securely sends the secret key to the other entity. (Or
each entity can generate a key and send it to the other entity,
where the two keys are combined to form a session key.) For
example, a message originator can generate a random session key
and then use the Rivest-Shamir-Adleman algorithm to encrypt that
key with the public key of the intended recipient. In key
agreement, the session key is not sent from one entity to another.
Instead, both entities, without prior arrangement except a public
exchange of data, each compute the same value; i.e., each
independently generates the same secret value, which cannot be
computed by third parties. For example, a message originator and
the intended recipient can each use their own private key and the
other's public key in the Diffie-Hellman algorithm to compute a
shared secret value, which then is used to derive a key to encrypt
the message.
Key Exchange Algorithm (KEA)
(N) A key agreement algorithm that is similar to the Diffie-
Hellman algorithm, uses 1024-bit asymmetric keys, and was
developed and formerly classified at the "Secret" level by NSA.
(Also see: CAPSTONE, CLIPPER, FORTEZZA, SKIPJACK.)
(C) On 23 June 1998, the NSA announced that KEA had been
declassified.
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key generator
(I) A device or algorithm that uses mathematical rules to
deterministically produce a pseudo-random sequence of
cryptographic keys.
key generation
(I) A process that creates the sequence of symbols that comprise a
cryptographic key. (Also see: key management.)
key length
(I) The number of symbols (usually bits) needed to be able to
represent any of the possible values of a cryptographic key.
key lifetime
(N) MISSI usage: 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. (Also see: cryptoperiod.)
key management
(I) The process of handling and controlling cryptographic keys and
related material (such as initialization values) during their life
cycle in a cryptographic system, including ordering, generating,
distributing, storing, loading, escrowing, archiving, auditing,
and destroying the material. (Also see: key distribution, key
escrow, public-key infrastructure.)
(O) "The generation, storage, distribution, deletion, archiving
and application of keys in accordance with a security policy."
[I7498 Part 2]
(O) "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]
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.)
key material identifier (KMID)
(N) MISSI usage: 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.
key pair
(I) A set of mathematically related keys--a public key and a
private key--that are used for asymmetric cryptography and are
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generated in a way that makes it computationally infeasible to
derive the private key from knowledge of the public key (e.g.,
see: Diffie-Hellman, Rivest-Shamir-Adleman).
(C) A key pair's owner discloses the public key to other system
entities so they can use the key to encrypt data, verify a digital
signature, compute a protected checksum, or generate a key in a
key agreement algorithm. The matching private key is kept secret
by the owner, who uses it to decrypt data, generate a digital
signature, verify a protected checksum, or generate a key in a key
agreement algorithm.
key recovery
(I) A process for learning the value of a cryptographic key that
was previously used to perform some cryptographic operation. (Also
see: cryptanalysis, 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.
key translation center
(I) A type of key center (used in a symmetric cryptography) that
implements a key distribution protocol to convey keys between two
(or more) parties who wish to communicate securely. (Also see: key
distribution center.)
(C) A key translation center translates 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 (by Alice) 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 keys in the KEK it shares with Bob, and either
sends that encrypted set to Alice for her to forward to Bob, or
sends it directly to Bob (although this direct distribution is not
supported in the ANSI standard [A9017]).
key transport (algorithm or protocol)
(I) A key establishment method by which a secret key is generated
by one entity in a communication association and securely sent to
another entity in the association. (Compare with: key agreement.)
(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]
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key update
(I) Derive a new key from an existing key. (Also see: certificate
rekey.)
key validation
(N) "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]
keyed hash
(I) A cryptographic hash in which the mapping to a hash result is
varied by a second input parameter that is a cryptographic key.
(C) If the input data set is changed, a new 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.
(C) There are least two forms of keyed hash: (a) A function based
on a keyed encryption algorithm. (For example, see: Data
Authentication Code.) (b) A keyless hash that is enhanced by
combining (for example, by concatenating) the input data set
parameter with a key parameter before mapping to a hash result.
keying material
(I) Data (such as key pairs and initialization values) needed to
establish and maintain a cryptographic security association.
KMID
See: key material identifier.
known-plaintext attack
(I) A cryptanalysis approach in which the analyst tries to
determine the key from knowledge of some plaintext-ciphertext
pairs (although the analyst may also know other clues, such as the
cryptographic algorithm).
L2F
See: Layer 2 Forwarding Protocol.
L2TP
See: Layer 2 Tunneling Protocol.
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.
label
See: security label.
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Law Enforcement Access Field (LEAF)
(N) A data item that is automatically embedded in data encrypted
by devices (e.g., see: CLIPPER chip) that implement the Escrowed
Encryption Standard.
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. (Also 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. (Also see: virtual
private network.)
(C) PPP can in turn encapsulate any OSI 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
See: Lightweight Directory Access Protocol.
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.
(C) This principle tends to limit damage that can be caused by an
accident, error, or unauthorized act.
Lightweight Directory Access Protocol (LDAP)
(N) A client-server protocol 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).
[R1777]
(C) 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
(I) Subnetwork usage: A point-to-point communication channel
connecting two computers, especially one between two subnetwork
packet switches that is implemented at OSI layer 2. (See: link
encryption.)
(C) Switches assume that links are logically passive. If a switch
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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.
(I) World Wide Web usage: See: hyperlink.
link encryption, link-by-link encryption
(I) Stepwise 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
switch and decrypting when it arrives at the next host or switch.
Each link may use a different key or even a different algorithm.
(Also see: end-to-end encryption.)
logic bomb
(I) Malicious logic that activates when specified conditions are
met and causes denial of service or damage to system resources.
(Also see: Trojan horse, virus, worm.)
LOTOS
See: Language of Temporal Ordering Specification.
MAC
See: Message Authentication Code.
malicious logic
(I) Hardware, software, or firmware that is intentionally included
or inserted in a system for a harmful purpose. (Also see: logic
bomb, Trojan horse, virus, worm.)
malware
(C) A contraction of "malicious software" (see: malicious logic).
Internet Standards Process documents SHOULD NOT use this term
because it is not listed in most dictionaries and might confuse
international readers.
man-in-the-middle attack
(I) A form of active wiretapping in which the attacker intercepts
and selectively modifies (or even blocks and deletes) communicated
data in order to masquerade as one or more of the entities
involved in a communication association. (Also see: hijack attack,
piggyback attack.)
(C) 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 block direct
communication between Alice and Bob, masquerade as Alice sending
data to Bob, masquerade as Bob sending data to Alice, establish
separate session keys with each of them, and then function as a
clandestine proxy server between them and capture or modify
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sensitive information that Alice and Bob think they are sending
only to each other.
mandatory access control (MAC)
(I) An access control service that enforces a security policy
based on comparing (a) security labels that indicate how sensitive
or critical system resources are with (b) security clearances that
authorize system entities to access certain resources. (Also see:
discretionary access control, rule-based security policy.)
(C) This kind of access control is called "mandatory" because an
entity that has clearance to access a resource may not, just by
its own volition, enable another entity to access that resource.
(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
(C) Internet Standards Process documents SHOULD NOT use this term
as a synonym for "checksum" because the word "manipulation"
implies protection against active attacks, which an ordinary
checksum might not provide. Instead, if such protection is
intended, refer to protected checksum or some particular type
thereof, depending on which is meant. If such protection is not
intended, refer to error detection code or some specific type of
checksum that is not protected.
masquerade attack
(I) A type of attack in which one system entity illegitimately
poses as (assumes the identity of) another entity. (Also see:
spoofing attack.)
MCA
See: merchant certificate 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. (Also see: message digest.)
MD4
(N) A cryptographic hash [R1320] that produces a 128-bit hash
result and was designed by Ron Rivest. (Also see: message digest
and SHA-1.)
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
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MD4.
merchant
(O) SET usage: "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 must have a relationship
with an acquirer. [SET1, SET2]
merchant certificate
(O) SET usage: 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 usage: 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. (Also see:
hierarchical PKI, trust-file PKI.)
message authentication code vs. Message Authentication Code (MAC)
1. (N) Capitalized: "The Message Authentication Code" refers to an
ANSI standard [A9009] for a checksum that is computed by a keyed
hash that is based on DES. (Also known as the U.S. Government
standard Data Authentication Code [FP113]).
(C) The ANSI standard MAC algorithm is equivalent to cipher block
chaining with IV = 0. MAC is also known as the U.S. Government
standard Data Authentication Code [FP113].
2. (C) Not capitalized: Internet Standards Process documents
SHOULD NOT use "message authentication code", because this 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.
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(C) The uncapitalized form is often misleadingly used as a synonym
for keyed hash. 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 primarily
serves a data integrity function rather than an authentication
function. 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
(C) Internet Standards Process documents SHOULD NOT use this term
as a synonym for "hash result" because it unnecessarily duplicates
the meaning of the other, more general term and mixes concepts in
a potentially misleading way. (See: cryptographic hash, Message
Handling System.)
Message Handling Systems `
(I) A ITU-T/ISO system concept, which 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
(C) Internet Standards Process documents SHOULD NOT use this term
as a synonym for "initialization value" because it mixes concepts
in a potentially misleading way.
message integrity check, message integrity code
(C) Internet Standards Process documents SHOULD NOT use these
terms because they mix concepts in a potentially misleading way.
(The word "message" is misleading because it suggests that the
mechanism is particularly suitable for or limited to electronic
mail. The word "code" is misleading because it suggests that
either encoding or encryption is involved, or that the term refers
to computer software.) Instead, use "checksum", "error detection
code", "hash", "keyed hash", "Message Authentication Code", or
"protected checksum", depending on what is meant.
Message Security Protocol (MSP)
(N) A secure message handling protocol [SDNS7] for use with X.400
and Internet mail protocols. Developed by NSA's Secure Data
Network System (SDNS) program and used in the U.S. Defense Message
System.
MHS
See: message handling system.
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MIME
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
specifications of PEM. (Also 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. [MISPC]
MISPC
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. (Also see: MSP.)
MISSI user
(O) MISSI usage: A system entity that is the subject of one or
more MISSI X.509 public-key certificates issued under a MISSI
certification hierarchy. (Also see: personality.)
(C) 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 must 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.
mode, mode of operation
(I) Encryption usage: 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: electronic codebook, cipher block
chaining, cipher feedback, output feedback.)
(I) System operation usage: 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.)
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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, Rivest-Shamir-Adleman.)
Morris Worm
(I) A worm program written by Robert T. Morris, Jr. that flooded
the ARPANET in November, 1988, causing problems for thousands of
hosts. (Also see: worm.)
MOSS
See: MIME Object Security Services.
MSP
See: Message Security Protocol.
multilevel secure (MLS)
(I) A class of system that has system resources (particularly
stored information) at more than one security level (i.e., has
different types of sensitive resources) and that permits
concurrent access by users who differ in security clearance and
need-to-know, but is able to prevent the users from accessing
resources for which they lack authorization.
multilevel security mode
(I) A mode of operation of an information system, that allows two
or more classification levels of information to be processed
concurrently within the same system when not all users have a
clearance or formal access authorization for all data handled by
the AIS.
(C) This mode is defined formally in U.S. Department of Defense
policy regarding system accreditation [DOD2], but the term is also
used outside the Defense Department and outside the Government.
Multipurpose Internet Mail Extensions (MIME)
(I) An Internet protocol [R2045] that enhances the basic format of
Internet electronic mail messages [R0822] to be able to use
character sets other than US-ASCII for textual headers and text
content, and to carry non-textual and multi-part content. (Also
see: S/MIME.)
National Computer Security Center (NCSC)
(N) A U.S. Department of Defense organization, housed in NSA, that
has established criteria for, and performed evaluations of,
computer and network systems that have a trusted computing base.
(See: Rainbow Series, TCSEC.)
National Information Assurance Partnership (NIAP)
(N) An organization created by NIST and NSA to enhance the quality
of commercial products for information security and increase
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consumer confidence in those products through objective evaluation
and testing methods.
(C) NIAP is registered, through the U.S. Department of Defense, 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 agency that promotes U.S.
economic growth by working with industry to develop and apply
technology, measurements, and standards, including standards for
INFOSEC. (Also see: ANSI, DES, DSA, DSS,, FIPS.)
National Security Agency (NSA)
(N) A U.S. Department of Defense intelligence agency that has
primary Government responsibility for INFOSEC for classified and
sensitive information handled by national security systems. (Also
see: FORTEZZA, KEA, MISSI, SKIPJACK.)
need-to-know
(I) The necessity for access to, knowledge of, or possession of
specific information required to carry out official duties.
(C) This 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
See: computer network.
NIAP
See: National Information Assurance Partnership.
NIST
See: National Institute of Standards and Technology.
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NLSP
Network Layer Security Protocol. An OSI protocol (IS0 11577) for
end-to-end encryption services at the top of OSI layer 3. NLSP is
derived from an SDNS protocol, SP3, but is much more complex.
no-lone zone
(I) A room or other space to which no person may have
unaccompanied access and that, when occupied, must be occupied by
two or more appropriately authorized persons. (Also see: dual
control.)
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 (extension of certificate).
non-repudiation service
(I) A security service that provide protection against false
denial of involvement in a communication. (Also see: repudiation.)
(C) There are two basic kinds of service:
- "Non-repudiation with proof of origin" 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.
- "Non-repudiation with proof of receipt" 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.
no-PIN ORA (NORA)
(O) MISSI usage: 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.
NORA
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, and delivery. [I7498 Part 2] (Also
see: digital notary.)
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OAKLEY
(I) An Internet IPsec key establishment protocol, based on the
Diffie-Hellman algorithm and designed to be a compatible component
of ISAKMP, that in addition to securely sharing a secret key
between two entities, provides authentication service to ensure
the entities of each other's identity, even if the exchange is
attacked by active wiretapping. (Superseded by IPsec Key
Exchange.)
(C) Establishes a shared key with an assigned identifier and
associated authenticated identities for two parties. Each key is
associated with algorithms used for authentication,
confidentiality, and one-way functions. Related to STS, sharing
the similarity of authenticating the Diffie-Hellman exponentials
and using them for determining a shared session key, and also of
achieving public-key forward secrecy for the shared key. 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) Trusted computer system modeling usage: A system element that
contains or receives information. (Also see: Bell-LaPadula Model,
trusted computer system.)
object identifier (OID)
(I) An official, globally unique name for a thing, written as a
sequence of integers formed and assigned as defined in the ASN.1
standard and used to reference the thing in abstract
specifications and during the negotiation of security services in
a protocol.
(O) "A value (distinguishable for all other such values) which is
associated with an object." [X680]
(C) 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.
(C) The tree has three arcs immediately below the root: {0} for
use by ITU-T, {1} for ISO, and {2} for 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
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8}.
(C) The following are additional examples: ANSI registers
organization names below the branch {joint-iso-ccitt(2)
country(16) US(840) organization(1)}. The NIST Computer Security
Object Register records PKI objects below the branch {joint-iso-
ccitt(2) country(16) us(840) gov(101) csor(3) pki(4)}. The U.S.
Department of Defense registers INFOSEC objects below the branch
{joint-iso-ccitt(2) country(16) us(840) organization(1) gov(101)
dod(2) infosec(1)}. The OID for the PKIX private extension is
defined in an arc below the arc for the PKIX name space, as
{iso(1) identified-organization(3) dod(6) internet(1) security(5)
mechanisms(5) pkix(7) 1 1}.
object reuse
(N) "The reassignment and reuse of a storage medium (e.g., page
frame, disk sector, magnetic tape) that once contained one or more
[information] objects. To be securely reused and assigned to a new
subject, storage media must contain no residual data (magnetic
remanence) from the object(s) previously contained in the media."
[NCS04]
OCSP
See: On-line Certificate Status Protocol.
OFB
See: output feedback.
ohnosecond
(C) That minuscule fraction of time in which you realize that your
private key has been compromised.
OID
See: object identifier.
On-line Certificate Status Protocol (OCSP)
(I) An Internet protocol used by a client to obtain from a server
the validity status and other information concerning a digital
certificate.
(C) In some applications, such as those involving high-value
commercial transactions, it may be necessary to obtain certificate
revocation status that is more timely than is possible with CRLs
or 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.
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one-time pad
(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.
(C) 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. 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. Capitalized: "One-Time Password" is an Internet protocol 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 other processes that need protection against
replay attacks. [R1938]
one-way encryption
(I) Irreversible transformation of plaintext to ciphertext, such
that the plaintext cannot be recovered from the ciphertext by
other than exhaustive procedures even if the cryptographic key is
known. (Also 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]
(C) Internet Standards Process documents SHOULD NOT use this term
as a synonym for "cryptographic hash".
open security environment
(O) DoD usage: A system environment that meets at least one of the
following 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
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during the operation of system applications. [NCS04] (Also see:
closed security environment.)
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.
(C) OSI-based standards include communication protocols that are
mostly incompatible with the Internet Protocol Suite, but also
include security models, such as X.509, that are used in the
Internet.
(C) The OSIRM layers, from highest to lowest, are (7) Application,
(6) Presentation, (5) Session, (4) Transport, (3) Network, (2)
Data Link, and (1) Physical. In this Glossary, these layers are
referred to by number to avoid confusing them with Internet
Protocol Suite layers, which are referred to by name.
(C) The OSI layers correspond [original author unknown] 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
ATM, 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.
(C) John G. Fletcher discovered that the OSI layers also
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
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attention.
1. Bashful: Physical quietly does it work, unnoticed by the
others.
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.
OPSEC
See: operations security.
ORA
See: organizational registration authority.
Orange Book
(C) Internet Standards Process documents 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 conventional abbreviation,
"TCSEC". (See: (usage note under) Green Book.)
organizational certificate
(O) MISSI usage: A type of MISSI X.509 public-key certificate that
is issued to support organizational message handling for the U.S.
Government's Defense Message System.
organizational registration authority (ORA)
(I) General usage: An RA for an organization.
(O) MISSI usage: The MISSI implementation of RA. A MISSI end
entity that 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 may also assist with
card management functions. An ORA is a local administrative
authority, and the term refers both to the office or role, and to
the person who fills that office. An ORA does not sign
certificates, CRLs, or CKLs. (Also see: no-PIN ORA, SSO-PIN ORA,
user-PIN ORA.)
origin authentication, origin authenticity
(C) Internet Standards Process documents SHOULD NOT use these
terms because they looks like careless use of an internationally
standardized term. Instead, use "data origin authentication" or
"data origin authentication service".
OSI, OSIRM
See: Open Systems Interconnection Reference Model.
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OTP
See: One-Time Password.
output feedback (OFB)
(N) A block cipher mode [FP081] that modifies electronic codebook
mode to operate on plaintext segments of variable length less than
or equal to the block length.
(C) 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.
outsider attack
See: (secondary definition in) attack.
P1363
See: IEEE P1363.
PAA
See: policy approving authority.
packet filter
See: (secondary definition in) filtering router.
PAN
See: primary account number.
PAP
See: Password Authentication Protocol.
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 information handled by the
system. (This mode is defined formally in U.S. Department of
Defense policy regarding system accreditation [DOD2].)
passive attack
See: (secondary definition in) attack.
passive wiretapping
See: (secondary definition in) wiretapping.
password
(I) A secret data value, usually a character string, that is used
as authentication information. (Also see: challenge-response.)
(C) A password is usually matched with a user identifier that is
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explicitly presented in the authentication process, but in some
cases the identity may be implicit.
(C) Using a password as authentication information assumes that
the password is known only by the system entity whose identity is
being authenticated. Therefore, in a network environment where
wiretapping is possible, simple authentication that relies on
transmission of static (repetitively used) passwords as cleartext
is inadequate. (Also see: one-time password, strong
authentication.)
Password Authentication Protocol (PAP)
(I) A simple authentication mechanism in PPP, in which a user
identifier and password are transmitted in cleartext. [R1334]
(Also see: CHAP.)
password sniffing
(I) Passive wiretapping, usually on local area network, to gain
knowledge of passwords. (See: (usage note in) sniffing.)
path discovery
(I) For a given digital certificate, the process of finding a set
of public-key certificates that comprise a certification path from
a trusted key to that digital certificate.
path validation
(I) The process of validating all of the digital certificates in a
certification path and the required relationships between those
certificates, thus validating the contents of the last certificate
on the path. (Also see: certificate validation.)
payment card
(N) SET usage: 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 usage: 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 usage: 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]
(Also see: PCA.)
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PC card
(N) A plug-in peripheral device, originally developed for portable
computers, that provides for functional expansion--such as
removable storage, modems, device interface adapters, and
cryptographic modules--in an internationally standardized, non-
proprietary form factor about the size of a credit card. (Also
see: FORTEZZA, PCMCIA.)
(C) The PC Card Standard defines a 68-pin interface between the
peripheral and the socket and defines three standard sizes, Types
I, II and III. All three 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.
PCA
(C) Internet Standards Process documents SHOULD NOT use this
acronym without a qualifying adjective because that would be
ambiguous. (See: Internet policy certification authority, (MISSI)
policy creation authority, (SET) payment gateway certification
authority.)
PCMCIA
(N) Personal Computer Memory Card International Association, an
international 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.
peer entity authentication
(I) "The corroboration that a peer entity in an association is the
one claimed." [I7498 Part 2] (Also see: authentication.)
peer entity authentication service
(I) A security service that verifies an identity claimed by or for
a system entity in an association. (Also see: authentication,
authentication service.)
(C) 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.
(C) See: "relationship between data integrity service and
authentication services" under data integrity service.
PEM
See: Privacy Enhanced Mail.
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penetration
(I) Successful, repeatable, unauthorized access to a protected
system resource. (Also see: attack, violation.)
penetration test
(I) A system test, often part of system certification, in which
evaluators attempt to circumvent the security features of the
system. [NCS04]
(C) Penetration testing may be performed under various constraints
and conditions. However, for a TCSEC evaluation, testers 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
See: (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. (Also see: color change.)
permission
(I) A synonym for "authorization", but "authorization" is
preferred in the PKI context.
personal identification number (PIN)
(I) A character string used as a password to gain access to a
system resource. (Also see: authentication information.)
(C) Despite the words "identification" and "number", a PIN seldom
serves as a user identifier, and a PIN's characters are not
necessarily all numeric. A better name for this concept would have
been "personal authentication system string (PASS)".
(C) Retail banking applications commonly use 4-character PINs.
FORTEZZA PC card's use up to 12 characters for user or SSO PINs.
personality, personality label
(O) MISSI usage: 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.
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(C) 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 BALL
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.
personnel security
(I) Procedures to ensure that persons who access a system have
proper authorization, clearance, and need-to-know as required by
the system's security policy.
PGP(trademark)
See: Pretty Good Privacy.
Photuris
(I) A UDP-based, key establishment protocol for session keys,
designed for use with the IPsec protocols AH and ESP. Superseded
by IKE.
phreak, phreaking
(C) A contraction (phone + break) that refers to penetration of a
telephone system or other communication system; also a pun on
freak. Internet Standards Process documents SHOULD NOT use this
term because the term is not listed in most dictionaries and might
confuse international readers.
physical security
(I) Fences, walls, locks, vaults, human guards and guard dogs,
sensors and alarms, and other tangible means of preventing
unauthorized physical access to a system.
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. (Also see: hijack attack, man-in-the-middle
attack.)
PIN
See: personal identification number.
ping of death
(I) An attack that sends an improperly large Internet Control
Message Protocol (ICMP) [R0792] echo request packet (a "ping")
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with the intent of overflowing the input buffers of the
destination machine and causing it to crash.
ping sweep
(I) An attack that sends Internet Control Message Protocol (ICMP)
[R0792] echo requests ("pings") to range of IP addresses, with the
goal of finding hosts that can be probed for vulnerabilities.
PKCS
See: Public-Key Cryptography Standards.
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.
PKCS #10
(N) A standard [PKC10] from the PKCS series; defines a syntax for
requests for public-key certificates. (Also see: certification
request.)
(C) 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 (pronounced "crypto-key"; short for
"cryptographic token interface") for devices that hold
cryptographic information and perform cryptographic functions.
PKI
See: public-key infrastructure.
PKIX
(I) (1.) A contraction of "Public-Key Infrastructure (X.509)", the
name of the IETF working group that is specifying an architecture
and set of protocols needed to support an X.509-based PKI for the
Internet. (2.) A collective name for that architecture and set of
protocols.
(C) 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
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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 a private extension to identify an on-line
verification service supporting the issuing CA.
plaintext
(I) Data that is input to and transformed by an encryption
process, or that is output by a decryption process.
(C) Usually, the plaintext input to an encryption operation is
cleartext. But in some cases, the input is ciphertext that was
output from another encryption operation. (Also see:
superencryption.)
Point-to-Point Protocol (PPP)
(I) An Internet protocol [R1661] for encapsulation and full-duplex
transportation of network layer protocol (mainly OSI layer 3) data
packets over a link between two peers, and for multiplexing
different network layer protocols over the same link. Includes
optional negotiation to select and use a peer entity
authentication protocol to authenticate the peer to each other
before they exchange network layer data. (Also see: CHAP, EAP,
PAP.)
Point-to-Point Tunneling Protocol (PPTP)
(I) An Internet client-server protocol (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. (Also see: L2TP.)
(C) PPP can in turn encapsulate any or IPS network layer protocol
(or OSI 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 (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 (the PPTP
Network Server, which runs on a general-purpose host).
policy
(C) Internet Standards Process documents SHOULD NOT this word as
an abbreviation for either "security policy" or "certificate
policy"; instead, to avoid misunderstanding, use the full term.
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policy approving authority (PAA)
(O) MISSI usage: The top-level signing authority of a MISSI
certification hierarchy. The term refers both that authoritative
office or role, and to the person who fills that office. (Also
see: root registry.)
(C) 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 Internet Policy Registration
Authority (IPRA). Each PCA operates in accordance with its
published security policy (see: certification practice statement)
and within constraints established by the IPRA for all PCAs.
[R1422]. (Also see: policy creation authority.)
policy creation authority (MISSI PCA)
(O) MISSI usage: 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 that authoritative office or role, and to the person who
fills that office. (Also see: policy certification authority.)
(C) A MISSI PCA's certificate is issued by a policy approving
authority. 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 and CKLs for its domain.
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]
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.
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.
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(C) P1003.1 supports security functionality like those on most
UNIX systems, including discretionary access control and
privilege. IEEE Draft Standard P1003.6.1 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.
PPP
See: Point-to-Point Protocol.
PPTP
See: Point-to-Point Tunneling Protocol.
pre-authorization
(I) A capability of a CA that enable certification requests to be
automatically validated against data provided in advance to the CA
by an authorizing entity.
Pretty Good Privacy(trademark) (PGP(trademark))
(O) Trademarks of Network Associates, Inc., referring to a
computer program and related protocols, that use cryptography to
provide data security for electronic mail and other applications
on the Internet. (Also see: MOSS, PEM, S/MIME.)
(C) 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. (Compare with:
Privacy Enhanced Mail.)
primary account number (PAN)
(O) SET usage: "The assigned number that identifies the card
issuer and cardholder. This account number is composed of an
issuer identification number (see: bank identification number), an
individual account number identification, and an accompanying
check digit as defined by ISO 7812-1985." [SET2, IS7812]
(C) 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 bank identification number part of the
PAN is the American Bankers Association.
privacy
(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. (Also see:
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anonymity.)
(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]
(C) Internet Standards Process documents 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 Enhanced Mail (PEM)
(I) An Internet protocol to provide data confidentiality, data
integrity, and data origin authentication for electronic mail.
[R1421, R1422]. (Also see: MOSS, MSP, PGP, S/MIME.)
(C) PEM encrypts messages with DES in CBC mode; provides key
distribution of DES keys by encrypting them with RSA; and signs
messages with RSA and 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. (Compare with: Pretty Good Privacy.)
(C) PEM is designed to be compatible with a wide range of key
management methods, but is limited by specifying security services
only for text messages and, like MOSS, has not been widely
implemented in the Internet.
private component
(I) A synonym for "private key".
(C) Internet Standards Process documents SHOULD NOT use this term;
to avoid confusing readers, use "private key" instead. However,
the term MAY be used when specifically discussing a key pair;
e.g., "A key pair has a public component and a private component."
private extension
See: (secondary definition in) extension.
private key
(I) The secret component of a pair of cryptographic keys used for
asymmetric cryptography. (Also see: key pair, public key.)
(O) "(In a public key cryptosystem) that key of a user's key pair
which is known only by that user." [X509]
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privilege
(I) An authorization or set of authorizations to perform security-
relevant functions, especially in the context of a computer
operating system.
procedural security
(C) Internet Standards Process documents SHOULD NOT use this term.
Instead, use "administrative security".
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 set by means that
protect against active attacks that would attempt to change the
checksum to make it match changes made to the data set. (Also see:
digital signature, keyed hash, (discussion under) checksum.
protected distribution system
(I) A wireline or fiber-optic system that includes sufficient
safeguards (acoustic, electric, electromagnetic, and physical) to
permit its use for unencrypted transmission of (cleartext) data.
protocol
(I) A set of formats and procedures to implement and control some
type of data exchange (i.e., data communication) between systems.
(For example, see: Internet Protocol.)
(C) More generally, a series of ordered steps involving computing
and communication 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. (Also see: Internet, OSI.)
proxy server
(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. (Also see: SOCKS.)
(C) 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
connecting directly to an external server, the 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,
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forwards the request to the remote 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.
(C) 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 OSI
layer 7 can also provide finer-grained security service than can a
filtering router at OSI layer 3. For example, an FTP proxy could
permit transfers out of, but not into, a protected network, or
vice versa.
pseudo-random
(I) A sequence of values that appears to be random (i.e.,
unpredictable) but is actually generated by a deterministic
algorithm.
pseudo-random number generator
(I) A process used to deterministically generate a series of
numbers (usually integers) that appear to be random according to
certain statistical tests, but actually are pseudo-random.
(C) Pseudo-random number generators are usually implemented in
software.
public component
(C) Internet Standards Process documents SHOULD NOT use this term
as a synonym for "public key" except when discussing a key pair.
public key
(I) The publicly-disclosable component of a pair of cryptographic
keys used for asymmetric cryptography. (Also see: key pair,
private key.)
(O) "(In a public key cryptosystem) that key of a user's key pair
which is publicly known." [X509]
public-key certificate
(I) A digital certificate that binds a system entity's identity to
a public key value, and possibly to additional data items; a
digitally-signed data structure that attests to the ownership of a
public key. (Also see: X.509 public-key certificate.)
(C) 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
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the certificate's data integrity.
(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]
public-key cryptography
(I) The popular synonym for "asymmetric cryptography".
Public-Key Cryptography Standards (PKCS)
(I) A series of specifications published by RSA Laboratories for
data structures and algorithm usage for basic applications of
asymmetric cryptography. (Also see: PKCS #7, PKCS #10, PKCS #11.)
(C) The PKCS were begun in 1991 in cooperation with industry and
academia, originally including Apple, Digital, Lotus, Microsoft,
Northern Telecom, Sun, and MIT. Today, these specifications are
widely used, but they are not sanctioned by an official standards
organizations, such as ANSI and ITU-T. 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.
(C) 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
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.
(C) 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:
(C) 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
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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.
(C) 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. 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.
(C) 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.
(C) Ordinary forward secrecy vs. "perfect" forward secret: Experts
disagree about the difference between these two. Some say there is
no difference. Others 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.
(C) 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)
(I) A system of CAs (and, optionally, RAs and other supporting
servers and agents) that perform some set of certificate
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management, archive management, key management, and token
management functions for a community of users in an application of
asymmetric cryptography. (Also see: hierarchical PKI, mesh PKI,
security management infrastructure, trust-file PKI.)
(O) PKIX usage: The set of hardware, software, people, policies,
and procedures needed to create, manage, store, distribute, and
revoke digital certificates based on asymmetric cryptography.
(C) The core PKI functions are to register users and issue their
public-key certificates, revoke certificates when required, and
archive data needed to validate certificates at a much later time.
Key pairs may be generated 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, since 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.
(C) 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.
RA
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.
(C) This capability might be used to restrict access to private
authorization data that is provided with a certificate request;
and distribute the responsibility to review and approve
certificate requests in high volume environments among multiple
RAs. RA domains might segregate certificate requests according to
an attribute of the certificate subject, such as an organizational
unit
RADIUS
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 National Computer Security Center,
that discuss in detail the Trusted Computer System Evaluation
Criteria and provide guidance for meeting and applying those
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requirements. (See: Green Book, Orange Book, Red Book, Yellow
Book.)
random
(I) In essence, random means unpredictable. A sequence of values
is called random if each successive value is obtained merely by
chance and does not depend on the preceding values of the
sequence, and each individual value is called random if each of
the values in the total population of possibilities has equal
probability of being selected. (Also see: cryptographic key,
pseudo-random.)
random number generator
(I) A process used to generate an unpredictable, uniformly
distributed series of numbers (usually integers). (Also see:
pseudo-random, random.)
(C) True random number generators are hardware-based devices that
depend on the output of a "noisy diode" or other physical
phenomena. [R1750]
RC2, RC4
See: Rivest Cipher #2, Rivest Cipher #4.
realm
(O) Kerberos usage: 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
RED
(I) Designation for information system equipment or facilities
that handle (and for data that contains) only plaintext (or,
depending on the context, classified information), and for such
data itself. This term derives from U.S. Government COMSEC
terminology. (Compare with: BLACK. Also see: RED/BLACK
separation.)
Red Book
(C) Internet Standards Process documents SHOULD NOT use this term
as a synonym for "Trusted Network Interpretation of the Trusted
Computer System Evaluation Criteria" [NCS05]. Instead, use the
full proper name of the document or, in subsequent references, a
conventional abbreviation. (Also see: TCSEC, Rainbow Series,
(usage note under) Green Book).
RED/BLACK separation
(I) An architectural concept for cryptographic systems that
strictly separates the parts of a system that handle plaintext
(RED information) from the parts that handle ciphertext (BLACK
information). This term derives from U.S. Government COMSEC
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terminology. (Also see: BLACK, RED.)
reference monitor concept
(I) "An access control concept that refers to an abstract machine
that mediates all accesses to objects by subjects." [NCS04]
reflection attack
(I) A type of replay attack in which transmitted data is sent back
to its originator.
register, registration
(I) An administrative act or process whereby a 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. (Also see: registration authority.)
(C) Registration can 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 authenticating the entity's identity and
verifying the correctness of the other attributes, in accordance
with the CA's CPS.
(C) 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.
- Permitted forms of names, such as DN, domain name, or IP
address.
- Whether names must 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 must appear before the CA or RA, or can be
represented by an agent.
- Whether and how an entity proves possession of the private key
matching a public key.
registration authority (RA)
(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
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certificates and CRLs and to perform other certificate management
functions. (Also see: organizational registration authority,
registration.)
(C) 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
talks 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. (Also 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 also be assigned to a
PKI element that is separate from both the CA and the RA.
(I) PKIX usage: An optional PKI component, separate from the
CA(s). The functions which the RA may carry out will vary from
case to case but may include personal authentication, token
distribution, revocation reporting, name assignment, key
generation, and archiving of key pairs. [R2510]
(O) SET usage: "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.
rekey
(I) Change the value of a cryptographic key that is being used in
an application of a cryptographic system. (See: certificate
rekey.)
(C) For example, rekey is required at the end of a cryptoperiod or
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key lifetime.
relying party
(I) A synonym for "certificate user". Used in a legal context
(see: ABA Guidelines) to mean a recipient of a certificate who
acts in reliance on that certificate.
Remote Authentication Dial-In User Service (RADIUS)
(I) An Internet protocol 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. [R2138] (Also
see: TACACS.)
(C) 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. (Also see: active wiretapping.)
repository
(I) A server system for storing and distributing digital
certificates and related information (including CRLs, CPSs, and
certificate policies) to certificate users.
(O) "A trustworthy system for storing and retrieving certificates
or other information relevant to certificates." [ABA]
(C) 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
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
(I) Denial by a system entity that was involved in an association
(especially an association that transfers information) of having
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participated in the relationship. (Also see: accountability, non-
repudiation service.)
(O) "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 Internet Standards documents and other
publications of the Internet Engineering Steering Group, the
Internet Architecture Board, and the Internet community in
general. [R1543]
(C) This term does not mean the same as "Internet Standard".
residual risk
(I) The risk that remains after countermeasures have been applied.
restore
See: card restore.
revocation
See: certificate revocation.
revocation date
(N) In an X.509 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. (Also see: invalidity date.)
(C) 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 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
See: certificate revocation.
RFC
See: Request for Comment.
risk
(I) An expectation of loss expressed as the probability that a
particular threat will exploit a particular vulnerability with a
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particular harmful result.
(O) SET usage: "The possibility of loss because of one or more
threats to information (not to be confused with financial or
business risk)." [SET2]
risk analysis, risk assessment
(I) A process that systematically identifies valuable system
resources and threats to those resources, quantifies loss
exposures based on estimated frequencies and costs of occurrence,
and (optionally) recommends how to allocate resources to
countermeasures to minimize total exposure.
(C) The analysis lists risks in order of cost and criticality,
thereby determining where countermeasures should be applied first.
It is usually financially and technically infeasible to counteract
all aspects of risk, and so some residual risk will remain, even
after all available countermeasures have been deployed.
risk management
(I) The process of identifying, controlling, and eliminating or
minimizing uncertain events that may affect system resources.
(Also see: risk analysis.)
Rivest Cipher #2 (RC2)
(N) A proprietary, variable-key-length block cipher invented by
Ron Rivest for RSA Data Security, Inc. (now a wholly-owned
subsidiary of Security Dynamics, Inc.).
Rivest Cipher #4 (RC4)
(N) A proprietary, variable-key-length stream cipher invented by
Ron Rivest for RSA Data Security, Inc. (now a wholly-owned
subsidiary of Security Dynamics, Inc.).
Rivest-Shamir-Adleman (RSA)
(N) An algorithm for asymmetric cryptography, invented in 1977 by
Ron Rivest, Adi Shamir, and Leonard Adleman [RSA78].
(C) RSA uses exponentiation modulo the product of two large prime
numbers. The difficulty of breaking RSA is believed to be
equivalent to the difficulty of factoring integers that are the
product of two large prime numbers of approximately equal size.
(C) 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).
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(C) 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 must be treated as part of the
private key, or else destroyed after computing n.)
(C) 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) = m to recover m.
(C) 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.
(C) 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 (as explained for 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.
role-based access control
(I) A form of identity-based access control where the system
entities that are identified and controlled are functional
positions in an organization or process.
root
(I) A CA that is directly trusted by an end entity. Acquiring the
value of a root CA's public key requires an out-of-band procedure.
(I) Hierarchical PKI usage: 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 trust. (Also
see: top CA.)
(C) In a hierarchical PKI, a root 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 must be securely
distributed to all certificate users in a way that does not depend
on the PKI's certification relationships. The root's public key
may be distributed simply as a numerical value, but typically is
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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.
(O) MISSI usage: 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 root called a Policy
Approving Authority.
(O) UNIX usage: A system 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.
root certificate
(I) Hierarchical PKI usage: The self-signed public-key certificate
at the top of a certification hierarchy. (Also see: root.)
root registry
(O) MISSI usage: A name previously used for a MISSI policy
approving authority.
router
(I) A computer that is a gateway between two networks at OSI layer
3 and that relays and directs data packets through that
internetwork. The most common form of router operates on IP
packets. (Also see: bridge.)
(I) Internet usage: In the context of the Internet protocol suite,
a networked computer that forwards Internet Protocol packets that
are not addressed to the computer itself. (Compare with: host.)
RSA
See: Rivest-Shamir-Adleman.
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] (Also see: identity-based
security policy.)
safety
(I) The property of a system being free from risk of causing harm
to system entities and outside entities.
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SAID
See: security association identifier.
salt
(I) A random value that is concatenated with a password before
applying the one-way encryption function used to protect passwords
that are stored in the database of an access control system. (Also
see: initialization value.)
(C) Salt protects a password-based access control system against a
dictionary attack.
sanitize
(I) Delete sensitive data from a file, a device, or a system; or
modify the data so as to be able to downgrade its classification
level.
SCA
See: subordinate certification authority.
scavenging
See: (secondary threat action definition in) threat consequence.
screening router
(I) A synonym for "filtering router".
SDE
See: Secure Data Exchange.
SDNS
See: Secure Data Network System.
seal
(C) To use cryptography to provide data integrity service for a
data set. (Also see: checksum, sign, wrap.) Internet Standards
Process documents SHOULD NOT use this term; instead, use a term
that is specific with regard to the mechanism(s) used.
secrecy, secret
(I) The condition of information being protected from being known
by any system entities except those who are intended to know it;
an item of information that is so protected.
(C) This term applies to symmetric keys, private keys, and
passwords.
secret-key cryptography
(I) A synonym for "symmetric cryptography".
Secure Data Exchange (SDE)
(N) A local area network security protocol defined by the IEEE
802.10 standard.
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Secure Data Network System (SDNS)
(N) An NSA program that developed security a for electronic mail
(Message Security Protocol), OSI layer 3 (SP3), OSI layer 4 (SP4),
and key management (KMP).
Secure Hash Standard (SHS)
(N) The U.S. Government standard [FP180] that specifies the Secure
Hash Algorithm (SHA-1), a cryptographic hash function that
produces a 160-bit output (hash result) for input data of any
length < 2**64 bits.
Secure-HTTP (S-HTTP)
(O) A protocol for HTTP security, proposed by CommerceNet, a
coalition of businesses interested in developing the Internet for
commercial uses. (Compare with: https.)
Secure/MIME (S/MIME)
(I) Secure/Multipurpose Internet Mail Extensions, an Internet
protocol developed by an industry consortium led by RSA Data
Security, Inc. (which is now a subsidiary of Security Dynamics
Technologies, Inc.). [R2633]
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. (Also see:
Transport Layer Security.)
(C) SSL is layered below HTTP (other Internet applications, such
as FTP, would be better served by IPsec) and above a reliable
transport protocol (TCP). SSL is independent of the application it
encapsulates, and a higher level protocol can layer on top of SSL
transparently. SSL itself 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 to negotiate a symmetric encryption
algorithm and secret session key (to use for data confidentiality)
before the application protocol transmits or receives data. A
keyed hash provides data integrity service for encapsulated data.
secure state
(I) A system condition in which no subject can access any object
in an unauthorized manner.
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security
(I) The property of system resources being free from unauthorized
access and from unauthorized or accidental change, destruction, or
loss.
security architecture
(I) A plan and set of principles that describe (a) the security
services that a system must provide to meet the needs of its
users, (b) the system elements needed to implement the services,
and (c) the performance levels needed in the elements to deal with
the threat environment.
(C) A security architecture is the result of applying the system
engineering process. A complete system security architecture
includes communication security, computer security, emanations
security, personnel security, physical security, and
administrative security. A complete security architecture must
deal with both intentional, intelligent threats and accidental
kinds of threats.
security association
(I) A relationship defined between two or more entities to enable
them to protect data they exchange. The relationship is used to
negotiate characteristics of protection mechanisms, but does not
include the mechanisms themselves. (Also see: association.)
(C) A security association describes how entities will use
security services. The relationship is represented by a set of
information that is shared between the entities and that must be
agreed upon and considered a contract between them.
(O) IPsec usage. A simplex (uni-directional) logical connection
created for security purposes and implemented with either AH or
ESP (but not both), which provide security services to data
carried by a connection. The security services offered by a
security association depend on the protocol selected, 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 destination IP address, a
protocol (AH or ESP) identifier, and a Security Parameter Index.
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 to
use for decryption or authentication at the destination. (Also
see: Security Parameter Index.)
security audit
(I) An independent review and examination of a system's records
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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]
(C) The basic audit objective is to establish accountability for
system entities that initiate or participate in security-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] (Also see: security
audit.)
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. (Also see:
clearance level.)
security compromise
(I) A security violation in which a system resource is exposed, or
is potentially exposed, to unauthorized access. (See: data
compromise, violation.)
security event
(I) A occurrence in a system that is relevant to the security of
the system.
(C) The term includes 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:
- 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.
- Logging the operator in or out.
- Failing a built-in hardware self-test or a software system
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integrity check.
security fault analysis
(I) A security analysis, usually performed on hardware at a gate
level, to determine the security properties of a device when a
hardware fault is encountered.
security gateway
(I) A gateway that separates trusted (or relatively more trusted)
hosts on the internal network side from untrusted (or less
trusted) hosts on the external network side. (Also see: firewall
and guard.)
(O) IPsec usage: "An intermediate system that implements IPsec
protocols." [R2401] Normally, AH or ESP is implemented to serve a
set of internal hosts, providing security services for the hosts
when they communicate with other, external hosts or gateways that
also implement IPsec.
security incident
(I) A system event that involves a security violation. (Also see:
security event.)
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
verifiable as correct." [NCS04]
security label
(I) A marking that is bound to a system resource and that names or
designates the security-relevant attributes of that resource.
[I7498 Part 2]
(C) The recommended definition is usefully broad, but usually the
term is understood more narrowly as a marking that represents the
security level of an information object, i.e., a marking that
indicates how sensitive an information object is. [NCS04]
(C) System security mechanisms interpret security labels according
to applicable security policy to determine how to control access
to the associated information, otherwise constrain its handling,
and affix appropriate security markings to visible (printed and
displayed) images thereof. [FP188]
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security level
(I) The combination of a hierarchical classification level and a
set of non-hierarchical category designations that represents how
sensitive information is. (Also see: dominate.)
security management infrastructure (SMI)
(I) System elements and activities that support security policy by
monitoring and controlling security services and mechanisms,
distributing security information, and reporting security events.
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. (Also see: public-key infrastructure.)
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 the system.
(C) Some examples of security mechanisms are encryption, digital
signature, authentication exchange, and traffic padding.
security parameters index (SPI)
(I) IPsec usage: The type of security association identifier used
in IPsec protocols. A 32-bit value used to distinguish among
different security associations terminating at the same
destination (IP address) and using the same IPsec 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.
security perimeter
(I) The boundary of the domain in which a security policy or
security architecture applies; i.e., the boundary of the space in
which security services are implemented to protect system
resources.
security policy
(I) A set of rules and practices that regulate how a system (or
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organization) provides security services to protect sensitive and
critical system resources. (Also see: discretionary access
control, identity-based security policy, mandatory access control,
rule-based security policy.)
(O) "The set of rules laid down by the security authority
governing the use and provision of security services and
facilities." [X509]
Security Protocol 3 (SP3)
(O) A protocol [SDNS3] developed by SDNS to provide connectionless
data security at the top of OSI layer 3. (Also see: 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 OSI layer 4. (Also see: TLSP.)
security-relevant event
See: security event.
security service
(I) A processing or communication service that is provided by a
system to give a specific kind of protection to system resources.
(Also 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.)
(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]
(C) Security services implement security policies, and are
implemented by security mechanisms.
security token
See: token.
security violation
(I) An act or event that disregards or breaks security policy.
(Also see: compromise, penetration.)
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.
(C) In a self-signed X.509 public-key certificate, the issuer's DN
is the same as the subject's DN.
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semantic security
(I) An attribute of a encryption algorithm that is a formalization
of the notion that the algorithm not only hides the plaintext but
also reveals no partial information about the plaintext. Whatever
is efficiently computable about the plaintext when given the
ciphertext, is also efficiently computable without the ciphertext.
(Also see: indistinguishability.)
sensitive (information)
(I) Information is sensitive if disclosure, alteration,
destruction, or loss of the information would adversely affect the
interests or business of its owner or user. (Also see: critical.)
separation of duties
(I) The practice of dividing the steps in a system function among
different individuals, so as to keep a single individual from
subverting the process. (Also see: dual control, administrative
security.)
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 key
(I) In the context of symmetric encryption, a key that is
temporary or is used for a relatively short period of time. (Also
see: key distribution center, master key.)
(C) Usually, a session key is used for a defined period of
communication between two computers, 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
must be rekeyed frequently.
SET
See: SET Secure Electronic Transaction(trademark).
SET private extension
(O) One of the private extensions for X.509 that are defined by
SET to carry information about a hashed root key, certificate
types, 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.
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(C) 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 URL where a copy of the policy statement may be found.
- An electronic mail address where a copy of the policy statement
may be found.
- A hash result of the policy statement, computed using the
indicated algorithm.
- 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. [SET]
(Also see: acquirer, brand, cardholder, dual signature, electronic
commerce, issuer, merchant, payment gateway, third party.)
(C) This term and acronym are trademarks of SETCo. MasterCard and
Visa announced the standard on February 1, 1996. On December 19,
1997, MasterCard and Visa formed SET Secure Electronic Transaction
LLC (commonly referred to as "SETCo") to implement the SET 1.0
specification. A memorandum of understanding also has been signed
that will eventually add American Express and JCB Credit Card
Company as co-owners of SETCo.
SETCo
See: (secondary definition in) SET Secure Electronic Transaction.
SHA-1
See: Secure Hash Standard.
shared secret
(I) A synonym for "keying material" or "cryptographic key".
S-HTTP
See: Secure HTTP.
sign
(I) Create a digital signature for a data set.
signature
See: digital signature.
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signer
(I) A human being or an organization entity that creates a digital
signature for a data set. [ABA]
SILS
See: Standards for Interoperable LAN/MAN Security.
simple authentication
(I) An authentication process that uses a password as the
information that verifies an identity claimed for an entity. (Also
see: strong authentication.)
(O) "Authentication by means of simple password arrangements."
[X509]
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.
(C) 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 of the entities to the other. The KEK is used with a
symmetric algorithm 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 for
moving electronic mail messages from one computer to another.
[R0821].
Simple Network Management Protocol (SNMP)
(I) A TCP-based, application-level, Internet Standard protocol for
conveying management information between managers and agents.
[R2570, R2574].
simple security property
See: (secondary definition in) 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
application systems after being authenticated just one time. (Also
see: Kerberos.)
(C) Typically, a user logs in just once, and then is transparently
granted access to a variety of permitted resources with no further
login being required until after the user logs out. Such a system
has the advantages of being user friendly and enabling
authentication to be managed consistently across an entire
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enterprise, and has the disadvantage of requiring all hosts to
trust the same authentication mechanism.
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.
(C) A v3 X.509 public-key certificate may have a "keyUsage"
extension which indicates the purpose for which the certified
public key is intended.
S/Key
(I) A system that uses a cryptographic hash function to generate a
sequence of 64-bit, one-time passwords for remote user login.
[R1760].
(C) The client generates a one-time password by applying MD4, a
cryptographic hash function, to the user's secret key multiple
times. 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 time
and comparing the hash result with the previously presented
password.
SKIP
See: Simple Key-management for IP.
SKIPJACK
(O) A Type II block cipher with a block size of 64 bits and a key
size of 80 bits, that was developed by NSA and formerly classified
at the "Secret" level. (Also see: CAPSTONE, CLIPPER, FORTEZZA, Key
Exchange Algorithm.)
(C) On 23 June 1998, the U.S. National Security Agency announced
that SKIPJACK had been declassified.
slot
(O) MISSI usage: One of the FORTEZZA PC card storage areas that
are each able to hold an X.509 certificate and information
associated with the certificate.
smart card
(I) A credit-card sized device containing one or more integrated
circuit chips, which perform the functions of a computer's
microprocessor, memory, and input/output interface. (Also see: PC
card.)
(C) Sometimes this term is used rather strictly to mean a card
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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 large,
especially cards that are much thicker, such as PC cards.
(C) A "smart token" is a device that conforms to the definition of
smart card, except that it is not have standard credit dimensions,
but is packaged in some other form convenient to be carried on
one's person, such as a dog tag or door key shape.
smart token
See: (secondary definition in) smart card.
SMI
See: security management infrastructure.
S/MIME
See: Secure/MIME.
SMTP
See: Simple Mail Transfer Protocol.
sniffing
(C) A synonym for "passive wiretapping". (Also see: password
sniffing.)
(C) Internet Standards Process documents SHOULD NOT use this term
because it unnecessarily duplicates the meaning of a term that is
better established. (Also see: (usage note under) Green Book.
SNMP
See: Simple Network Management Protocol.
social engineering
(C) A euphemism for non-technical or low-technology means--such as
lies, impersonation, tricks, bribes, blackmail, and threats--used
to attack and gain access to information systems. (Also see:
masquerade attack.) Internet Standards Process documents SHOULD
NOT use this term; instead, use a term that is specific with
regard to the means of attack.
SOCKS
(I) A 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.
(C) SOCKS is layered under the application layer and 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
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used, authenticates with the chosen method, 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.
software
(I) Computer programs (which are stored in and executed by
computer hardware) and associated data (which is stored in the
hardware) that may be dynamically written or modified during
execution. (Compare with: firmware, hardware.)
SORA
See: SSO-PIN ORA.
source integrity
(I) The degree of confidence that can be placed in information
based on the trustworthiness of its sources. (Also see:
integrity.)
SP3
See: Security Protocol 3.
SP4
See: Security Protocol 4.
spam
(I) (1.) Verb: to indiscriminately send unsolicited, unwanted,
irrelevant, or inappropriate messages, especially commercial
advertising in mass quantities. (2.) Noun: electronic "junk mail".
(C) This term must not be written 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 commercial email (UCE)], although 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."
(C) In sufficient volume, spam can cause denial of service. (Also
see: flooding.) According to the SPAM Web site, the term was
adopted as a result of the Monty Python skit in which a group of
Vikings sang a chorus of 'SPAM, SPAM, SPAM . . .' in an increasing
crescendo, drowning out other conversation. Hence, the analogy
applied because UCE was drowning out normal discourse on the
Internet.
SPC
See: software publisher certificate.
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SPI
See: Security Parameters Index.
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. (Also see: dual control,
split knowledge.)
split knowledge
(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. (Also see: dual
control, split key.)
(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) A synonym for "masquerade attack".
SSL
See: Secure Sockets Layer, Standard Security Label.
SSO
See: system security officer.
SSO PIN
(O) MISSI usage: 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 certification authority.
(Also see: user PIN.)
SSO-PIN ORA (SORA)
(O) MISSI usage: 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 an end user's
FORTEZZA PC card.
Standards for Interoperable LAN/MAN Security (SILS)
(N) (1.) The IEEE 802.10 standards committee. (2.) A developing
set of IEEE standards, which has eight parts: (a) Model, 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.
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Star Trek attack
(C) An attack that penetrates your system where no attack has ever
gone before.
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. (Also see:
cryptology.)
(C) An example of a steganographic method is "invisible" ink.
(Also see: digital watermark.)
storage channel
See: (secondary definition in) covert channel.
stream cipher
(I) An encryption algorithm that breaks plaintext into a stream of
successive bits (or characters) and encrypts the n-th plaintext
bit with the n-th element of a parallel key stream, thus
converting the plaintext bit stream into a ciphertext bit stream.
[Schn] (Compare with: block cipher.)
strong authentication
(I) An authentication process that uses cryptography--particularly
public-key certificates--to verify the identity claimed for an
entity. (Also see: X.509.)
(O) "Authentication by means of cryptographically derived
credentials." [X509]
subject
1. (I) In a computer system: A system entity that causes
information to flow among objects or changes the system state;
technically, a process-domain pair. (Also see: Bell-LaPadula
Model.)
2. (I) Of a 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 value in a public-key certificate.
subnetwork
(N) An OSI term for a system of packet relays and connecting links
that implement the lower three protocol layers of the OSIRM to
provide a communication service that interconnects attached end
systems. Usually the switches operate at OSI layer 3 and are all
of the same type (e.g., all X.25 packet switches, or all interface
units in an IEEE 802.3 LAN). (Also see: gateway, internet,
router.)
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subordinate certification authority (SCA)
(I) A CA whose public-key certificate is issued by another
(superior) CA.
(O) MISSI usage: The fourth-highest (bottom) level of a MISSI
certification hierarchy; a MISSI certification authority 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 distinguished name
(I) An X.500 DN is subordinate to another 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>.
superencryption
(I) An encryption operation for which the plaintext input to be
transformed is the ciphertext output of a previous encryption
operation.
symmetric cryptography
(I) A branch of cryptography involving algorithms that use the
same key for two different steps of the algorithm (such as
encryption and decryption, or signature creation and signature
verification).
(C) Symmetric cryptography has been used for thousands of years
[Kahn]. A modern example of is the U.S. Government's Data
Encryption Standard. Symmetric cryptography is sometimes called
"secret-key cryptography" (also see: public-key cryptography)
because the entities that share the key, such as the originator
and the recipient of a message, must keep the key secret. For
example, when Alice wants to ensure confidentiality for data she
sends to Bob, she encrypts the data with a secret key, and Bob
uses the same key to decrypt. Keeping the shared key secret
entails both cost and risk when the key must be distributed to
both Alice and Bob. Thus, symmetric cryptography has a key
management disadvantage compared to asymmetric cryptography. (Also
see: key agreement).
symmetric key
(I) A cryptographic key that is used in a symmetric cryptographic
algorithm.
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SYN flood
(I) A denial of service attack that sends a host more TCP SYN
packets (request to synchronize sequence numbers, used when
opening a connection) than the protocol implementation can handle.
(Also see: flooding.)
system entity
(I) An active element of a system--an automated process, a person,
or a group of persons--that incorporates some specific set of
capabilities.
system high
(I) The highest security level supported by a system at a
particular time or in a particular environment.
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.
(C) This mode is defined formally in U.S. Department of Defense
policy regarding 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 performs its intended
function in a unimpaired manner, free from deliberate or
inadvertent unauthorized manipulation." [NCS04] (Also see: 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. (Also see: system integrity.)
system low
(I) The lowest security level supported by a system at a
particular time or in a particular environment.
system resource
(I) Data contained in a 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., a system
component--hardware, firmware, software, or documentation); or a
facility that houses system operations and equipment.
system verification
See: (secondary definition in) verification.
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TACACS, TACACS+
See: Terminal Access Controller (TAC) Access Control System.
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.
TCB
See: trusted computing base.
TCP
See: Transmission Control Protocol.
TCP/IP
(I) A synonym for "Internet Protocol Suite", in which the
Transmission Control Protocol (TCP) and the Internet Protocol (IP)
are important parts.
TCSEC
See: Trusted Computer System Evaluation Criteria.
TELNET
(I) A TCP-based, application-level, Internet Standard protocol for
remote login from one host to another. [R0854]
TEMPEST
(O) A nickname for specifications and standards for limiting the
strength of electromagnetic emanations from electrical and
electronic equipment and thus reducing vulnerability to
eavesdropping. This term originated in the U.S. Department of
Defense.
(C) Internet Standards Process documents SHOULD NOT use this term
as a synonym for "emanations security".
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. Originally developed for
ARPANET and now evolved for use in commercial equipment:
- "XTACACS": The name of Cisco Corporation's implementation,
which enhances and extends the original TACACS.
- "TACACS+": 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. It
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is extensible to allow any authentication mechanism to be used
with TACACS+ clients.
(C) 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.
threat
(I) A potential for violation of security, which exists when there
is a circumstance, capability, action, or event that could breach
security and cause harm. (Also see: attack, threat action, threat
consequence.)
threat action
(I) An assault on system security. (Also see: attack, threat,
threat consequence.)
(C) A complete security architecture must deal with both
intentional acts (i.e. attacks) and accidental events [FIPS31].
threat consequence
(I) A security violation that results from a threat action.
Includes disclosure, deception, disruption, and usurpation. (Also
see: attack, threat, threat action.)
(C) The following subentries describe the types of threat actions
that cause each threat consequence. Threat actions that are
accidental events are marked by "*".
1. "(Unauthorized) Disclosure" (a threat consequence): A
circumstance or event whereby an entity gains access to data
for which the entity is not authorized (Also see: data
confidentiality.) The following threat actions can cause
unauthorized disclosure:
A. "Exposure": An action whereby sensitive data is directly
released to an unauthorized entity. This includes:
a. "Deliberate Exposure: Intentional release of sensitive
data to an unauthorized entity.
b. "Scavenging": Searching through data residue in a system
to acquire unauthorized knowledge of sensitive data.
c* "Human error": Human action or inaction that
unintentionally results in an entity receiving
unauthorized knowledge of sensitive data.
d* "Hardware/software error". System failure that results in
an entity receiving unauthorized knowledge of sensitive
data.
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B. "Interception": An action whereby an unauthorized entity
directly accesses sensitive data traveling between
authorized sources and destinations. This includes:
a. "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.
b. "Wiretapping (passive): Monitoring and recording data
that is flowing between two points in a communication
system. (Also see: wiretapping.)
c. "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. (Also see:
emanation.)
C. "Inference": An action whereby an unauthorized entity
indirectly accesses sensitive data (but not necessarily the
data contained in the communication) by reasoning from
characteristics or byproducts of communications. This
includes:
a. Traffic analysis: Gaining knowledge of data by observing
the characteristics of communications that carry the
data. (Also see: (main glossary entry for) traffic
analysis.)
b. "Signals analysis": Gaining indirect knowledge 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. (Also see:
emanation.)
D. "Intrusion": A threat consequence; an action whereby an
unauthorized entity gains access to sensitive data by
circumventing a system's security protections. This
includes:
a. "Trespass": Gaining unauthorized physical access to
sensitive data by circumventing a system's protections.
b. "Penetration": Gaining unauthorized logical access to
sensitive data by circumventing a system's protections.
c. "Reverse engineering": Acquiring sensitive data by
disassembling, and analyzing the design, of a system
component.
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d. Cryptanalysis: Transforming encrypted data into plaintext
without having prior knowledge of variables or algorithms
used in the encipherment process. (Also see: (main
glossary entry for) cryptanalysis.)
2. "Deception" (a threat consequence): A circumstance or event
that may result in an authorized entity receiving false data
and believing it to be true. The following threat actions can
cause deception:
A. "Masquerade": An action whereby an unauthorized entity gains
access to a system or performs a malicious act by posing as
an authorized entity.(Also see: (main glossary entry for)
masquerade attack.)
a. "Spoof": Attempt by an unauthorized entity to gain access
to a system by posing as an authorized user.
b. "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. (Also
see: (main glossary entry for) malicious logic.)
B. "Falsification": Action whereby false data deceives an
authorized entity. (Also see: active wiretapping.)
a. "Substitution": Altering or replacing valid data with
false data that serves to deceive an authorized entity.
b. "Insertion": Introducing or adding valid data with false
data that serves to deceive an authorized entity.
C. "Repudiation": Action whereby an entity deceives another by
falsely denying responsibility for an act. (Also see: non-
repudiation service, (main glossary entry for) repudiation.)
a. "False denial of origin": Action whereby the originator
of data denies responsibility for its generation.
b. "False denial of receipt": Action whereby the recipient
of data denies receiving and possessing the data.
3. "Disruption" (a threat consequence): A circumstance or event
that interrupts or prevents the correct option of system
services and functions. (Also see: denial of service.) The
following threat actions that can cause disruption:
A. "Incapacitation": Action that prevents or interrupts system
operation by disabling a system component.
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a. "Malicious logic": In context of disabling, any hardware,
firmware, or software (e.g., logic bomb) intentionally
introduced into a system to destroy system functions or
resources. (Also see: (main glossary entry for) malicious
logic.)
b. "Physical destruction": Deliberate destruction of a
system component to interrupt or prevent system
operation.
c* "Human error": Action or inaction that disables a system
component.
d* "Hardware or software error": Error that causes failure
of a system component and leads to disruption of system
operation.
e* "Natural catastrophe": Any "act of God" (e.g., fire,
flood, wind, or earthquake) that disables a system
component.
B. "Corruption": Action that undesirably alters system
operation by adversely modifying system functions or data.
a. "Tamper": In context of corruption, deliberate alteration
of a system's logic, data, or control information to
interrupt or prevent correct operation of system
functions.
b. "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. (Also see: (main glossary entry for)
malicious logic.)
c* "Human error": Human action or inaction that results in
the alteration of system functions or data.
d* "Hardware or software error": Error that results in the
alteration of system functions or data.
e* "Natural catastrophe": Any "act of God" (e.g., power
surge caused by lightning) that alters system functions
or data.
C. "Obstruction": Action that interrupts delivery of system
services by hindering system operations.
a. "Interference": Action that disrupts system operations by
blocking communications or user data or control
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information.
b. "Overload": Actions that hinders system operation by
placing excess burden on the performance capabilities of
a system component. (Also see: flooding.)
4. "Usurpation" (a threat consequence): A circumstance or event
that results in control of system services or functions by an
unauthorized entity. The following threat actions can cause
usurpation:
A. "Misappropriation": Action whereby an entity assumes
unauthorized logical or physical control of a system
resource.
a. "Theft of service": Unauthorized use of service by an
entity.
b. "Theft of functionality": Unauthorized acquisition of
actual hardware, software, or firmware of a system
component.
c. "Theft of data": Unauthorized acquisition and use of
data.
B. "Misuse": Action that causes a system component to perform a
function or service that is detrimental to system security.
a. "Tamper": In context of misuse, deliberate alteration of
a system's logic, data, or control information to cause
the system to perform unauthorized functions or services.
b. "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.
c. "Violation of permissions": Action by an entity that
exceeds the entity's system privileges by executing an
unauthorized function.
thumbprint
(I) A pattern of curves formed by the ridges on the tip of a
thumb. (Also see: biometric authentication, fingerprint.)
(C) Internet Standards Process documents SHOULD NOT use this term
as a synonym for "hash result" because it mixes concepts in a
potentially misleading way.
ticket
(I) A synonym for "capability".
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(C) 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 have been implemented with
symmetric cryptography (see: Kerberos), but can also be
implemented as attribute certificates using asymmetric
cryptography. In effect, an RA that does not issue digital
certificates itself, but vouches for the identity of prospective
certificate holders to a CA, is a ticket-granting agent. [FPKI]
timing channel
See: (secondary definition in) covert channel.
TLS
See: Transport Layer Security. (Also see: TLSP.)
TLSP
See: Transport Layer Security Protocol. (Also see: TLS.)
token
1. (I) General usage: 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.
2. (I) Authentication usage: A data object or a portable, user-
controlled, physical device used to verify an identity in an
authentication process. (Also see: authentication information,
dongle.)
3. (I) Cryptographic usage: See: cryptographic token.
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
card restore, the second card is initialized with its own,
different local security values such as PINs and card 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 token with data for
the purpose of recreating (duplicating) the contents previously
held by that or another token.
token storage key
(I) A cryptography key used to protect data that is stored on a
security token.
top CA
(I) A CA that is the highest level (i.e., is the most trusted CA)
in a certification hierarchy. (Also see: root.)
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]
traffic analysis
(I) Inference of information from observable characteristics of
data flow(s), even when the data 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. (Also
see: wiretapping.)
(O) "The inference of information from observation of traffic
flows (presence, absence, amount, direction, and frequency)."
[I7498 Part 2]
traffic flow confidentiality
(I) A data confidentiality service to protect against traffic
analysis.
(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
See: (secondary definition in) Bell-LaPadula Model.
Transmission Control Protocol (TCP)
(I) An Internet protocol [R0793] that reliably delivers a sequence
of datagrams (discrete sets of bits) from one computer to another
in a computer network.
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(C) TCP is designed to fit into a layered hierarchy of protocols
that support internetwork applications. TCP assumes it can obtain
a simple, potentially unreliable datagram service (such as the
Internet Protocol) from the lower level protocols.
Transport Layer Security (TLS)
(I) TLS Version 1.0 is an Internet protocol based-on and very
similar to SSL Version 3.0. (Compare with: TLSP.)
(C) The TLS protocol is misnamed, because it operates well above
OSI layer 4.
Transport Layer Security Protocol (TLSP)
(I) An end-to-end encryption (ISO 10736) protocol that provides
security services at the bottom of OSI layer 4, i.e., directly
above OSI layer 3. (Compare with: TLS.)
(C) TLSP evolved directly from the SP4 protocol of SDNS.
transport mode vs. tunnel mode
(I) IPsec usage: Two ways to apply IPsec protocols (AH and ESP) to
protect communications:
- "Transport mode": The protection applies mainly to the packets
of upper layer protocols, the ones that are carried above IP.
- "Tunnel mode": The protection applies to tunneled IP packets.
(C) A transport mode security association is always between two
hosts. A tunnel mode security association is one that is applied
to an IP tunnel, but the each end may be either a host or a
gateway; and, whenever either end of a security association is a
security gateway, the association must be in tunnel mode.
trap door
(I) A hidden computer flaw known to an intruder, or hidden
computer mechanism (usually software) installed by an intruder,
who can activate the mechanism to gain access to the computer
without being blocked by security mechanisms. (Also see: back
door, Trojan horse.)
triple DES
(I) An block cipher, based on DES, that transforms each 64-bit
plaintext block by applying the Data Encryption Algorithm three
successive times, using either two or three different keys, for an
effective key length of 112 or 168 bits. [ANSI X9.52] (Also see:
DES.)
(C) IPsec usage: The specific encryption algorithm proposed for
ESP uses a 168-bit key, consisting of three independent 56-bit
quantities used by the Data Encryption Algorithm, and a 64-bit
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initialization vector. Each datagram contains an IV to ensure that
each received datagram can be decrypted, even if other datagrams
are dropped or datagrams are reordered in transit. [R1851]
triple-wrapped
(I) S/MIME usage: 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.
trust
(I) Information system usage: Refers to 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. (Also see:
trust level.)
(C) trusted vs. trustworthy: In discussing a system or system
process or object, this glossary (and industry usage) prefers the
term "trusted" to describe a system that operates as expected,
according to design and policy. When the trust can also be
guaranteed in some convincing way, such as through formal analysis
or code review, the system is termed "trustworthy"; this differs
from the ABA Guidelines definition (see: trustworthy system).
(I) PKI usage: Describes the relationship between an certificate
user and a CA; a certificate user must trust that the CA creates
only valid digital certificates.
trust chain
(C) Internet Standards Process documents SHOULD NOT use this term
as a synonym for "certification path" because it mixes concepts
(see: trust) in a potentially misleading way.
trust-file PKI
(I) A non-hierarchical PKI in which a each certificate user has a
local file (used by application software) of public-key
certificates that the user trusts as starting points (see: root)
for certification paths. (Also see: hierarchical PKI, mesh PKI,
web of trust.)
(C) For example, popular browsers are distributed with an initial
file of trusted 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.
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trust hierarchy
(C) Internet Standards Process documents SHOULD NOT use this term
as a synonym for "certification hierarchy" because it mixes
concepts (see: trust) in a potentially misleading way and
duplicates the meaning of another, standardized term. (Also see:
web of trust.)
trust level
(I) A characterization of a standard of security protection to be
met by a computer system.
(C) The "Trusted Computer System Evaluation Criteria" defines
eight trust levels. From the lowest to the highest, they are D,
C1, C2, B1, B2, B3, and A1. A trust level is based not only on the
presence of security mechanisms but also on the use of systems
engineering discipline to properly structure the system and on
implementation analysis to ensure that the system provides the
appropriate degree of trust.
trusted
See: (discussion under) trust.
trusted certificate
(I) A certificate that is trusted a priori by a certificate user,
such as a public-key certificate that can be used to provide the
first public key in a certification path.
(C) A trusted public-key certificate might be the root certificate
in a hierarchical PKI, or the certificate of the CA that issued
the user's own certificate in a mesh PKI, or any certificate
accepted by the user in a trust-file PKI.
trusted computer system
(I) "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] (Also
see: (discussion under) trust.)
Trusted Computer System Evaluation Criteria (TCSEC)
(N) A standard for evaluating the security provided by operating
systems [CSC001, DOD1]. Informally referred to as the "Orange
Book" because of the color of its cover; first document in the
Rainbow Series. (See: (usage note under) Green Book, Orange Book,
trust level.)
(C) To be superseded by the Common Criteria.
trusted computing base (TCB)
(I) "The totality of protection mechanisms within a computer
system, including hardware, firmware, and software, the
combination of which is responsible for enforcing a security
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policy." [NCS04] (Also see: (discussion of "trusted" under)
trust.)
trusted key
(I) A public key that is trusted a priori by a user, such as a key
that can be used as the first public key in a certification path.
(C) A trusted public key can 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
(I) COMPUSEC usage: A mechanism by which a computer system user
can communicate directly and reliably with the trusted computing
base (TCB) and that can only be activated by the user or the TCB
and cannot be imitated by untrusted software within the computer.
[NCS04]
(I) COMSEC usage: 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
(I) A system process 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. (Also see: (discussion of "trusted" under) trust.)
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 channel--for
example, a LAN--is not being attacked by other means.)
trusted system
See: (discussion under) trust, trusted computer system,
trustworthy system.
Trusted Systems Interoperability Group (TSIG)
(N) A forum of computer vendors, system integrators, and users
devoted to promoting interoperability of trusted computer systems.
TSIG meetings are open to all persons who are working in the
INFOSEC area.
trustworthy system
(O) ABA usage: "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
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intended functions; and (d) adhere to generally accepted security
principles." [ABA] This differs somewhat from other industry usage
(see: (discussion of "trusted vs. trustworthy" under) trust).
TSIG
See: Trusted System Interoperability Group.
tunnel, tunneling
(I) A communication channel created in a computer network by
encapsulating (carrying, layering) a communication protocol's data
packets in (on top of) a second protocol that normally would be
carried above, or at the same layer as, the first one. (Also see:
L2TP, VPN.)
(C) Tunneling can involve almost any OSI or TCP/IP protocol
layers; for example, a TCP connection between two hosts could
conceivably be tunneled through email messages across the
Internet. Usually, a tunnel is a logical point-to-point link--
i.e., an OSI layer 2 connection--created by encapsulating the
layer 2 protocol in a n protocol (such as TCP), or in a OSI layer
3 internetwork protocol (such as IP), or in another layer 2
protocol. Often, encapsulation is accomplished with an
intermediate protocol (a tunneling protocol), such as L2TP,
layered between the tunneled layer 2 protocol and the
encapsulating protocol.
(C) Tunneling can 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. (Also see: virtual private
network).
(O) SET usage: The name of a SET private extension that indicates
whether the CA or the payment gateway supports passing encrypted
messages to the cardholder through the merchant. If so, the
extension lists OIDs of symmetric encryption algorithms that are
supported.
tunnel mode
(I) IPsec usage: See: transport mode.
two-person control
(I) The close surveillance and control of a system, 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. (Also see: dual control, no-lone zone.)
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Type I cryptography
(O) A cryptographic algorithm or device approved by the U.S.
National Security Agency for protecting classified information.
Type II cryptography
(O) A cryptographic algorithm or device approved by the U.S.
National Security Agency for protecting sensitive unclassified
information in systems (as specified in section 2315 of Title 10
United States Code, or section 3502(2) of Title 44, United States
Code.)
Type III cryptography
(O) A cryptographic algorithm or device approved as a Federal
Information Processing Standard.
UDP
See: User Datagram Protocol.
unclassified
(I) Not classified.
unencrypted
(I) Not encrypted.
unforgeable
(I) Cryptographic usage: The property of a cryptographic data
structure--i.e., a data structure that is computed using one more
cryptographic functions--that makes it computationally infeasible
to construct (i.e., compute) an unauthorized but correct value of
the structure without having knowledge of one of more keys (e.g.,
see: digital certificate).
(C) This definition is narrower than general English usage, in
which "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 attempts to verify the certificate signature
using the true public key of the claimed issuer.
uniform resource identifier (URI)
(I) A type of formatted identifier 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. [R1630]
(C) URIs are used in HTML to identify the target of hyperlinks. in
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common practice, URIs include uniform resource locators [R2368]
and relative URLs. [R1808].
uniform resource locator (URL)
(I) A type of formatted identifier that describes the access
method and location of an information resource object on the
Internet. [R1738]
(C) 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 a 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.
UORA
See: user-PIN ORA.
update
See: certificate update and key update.
URI
See: uniform resource identifier.
URL
See: uniform resource locator.
URN
See: uniform resource name.
user
(I) A person (or organization entity) or an automated process
(usually acting on behalf of a person that accesses a system,
whether authorized to do or not.
(C) Because this term can be understood in many ways, any Internet
Standards Process document that uses it SHOULD provide an explicit
definition.
User Datagram Protocol (UDP)
(I) An Internet Standard [R0768] protocol that provides a datagram
mode of packet-switched computer communication in an internetwork.
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(C) 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
services that TCP provides.
user identifier
(I) A character string or symbol that is used in a system to
uniquely name a specific user or group of users.
(C) Often verified by a password in an authentication process.
user PIN
(O) MISSI usage: One of two personal identification numbers 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.
(Also see: SSO PIN.)
user-PIN ORA (UORA)
(O) 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.
(Also see: no-PIN ORA, SSO-PIN ORA.)
usurpation
See: (secondary definition in) threat consequence.
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. (Also see: Coordinated Universal Time,
GeneralizedTime.)
v1 certificate
(C) Refers to either an X.509 public-key certificate in its
version 1 format, or an X.509 attribute certificate in its version
1 format. However, many people who use this term are not aware
that X.509 specifies attribute certificates that do not contain a
public key. IETF Standards Process documents MAY use this term as
an abbreviation for "version 1 X.509 public-key certificate", but
only after using the full term at the first instance. Internet
Standards Process documents SHOULD NOT use this term as an
abbreviation to mean "version 1 X.509 attribute certificate".
v1 CRL
(I) A synonym for and "X.509 CRL" in version 1 format.
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v2 certificate
(I) A synonym for an "X.509 public-key certificate" in version 2
format.
v2 CRL
(I) A synonym for an "X.509 CRL" in version 2 format.
v3 certificate
(I) A synonym for an "X.509 public-key certificate" in version 3
format.
valid certificate
(I) A digital certificate for which the binding of the data items
can be trusted; one that can be validated successfully. (See:
validate vs. verify.)
valid signature
(C) Internet Standards Process documents SHOULD NOT use this term;
instead, use "authentic signature". This Glossary recommends
saying "validate the certificate" and "verify the signature" (see:
validate vs. verify); therefore, it would be inconsistent to say
that a signature is "valid".
validate vs. verify
(C) The PKI community uses words inconsistently when describing
what a certificate user does to make certain that a digital
certificate can be trusted. Usually, we say "verify the signature"
but say "validate the certificate"; i.e., we "verify" atomic
truths but "validate" data structures, relationships, and systems
that are composed of or depend on verified items. Too often,
however, verify and validate are used interchangeably.
Internet Standards Process documents SHOULD follow these two rules
to ensure consistency and to align Internet security terminology
with general English usage:
Rule 1: Use "validate" when referring to a process intended to
establish the soundness or correctness of a construct, like a
public-key certificate or a certification path.
The rationale for Rule 1 is that "valid" derives from a word that
means "strong" in Latin. Thus, to validate means to make sure that
a construction is sound. A certificate user validates a public-key
certificate to establish trust in the binding that the certificate
asserts between an identity and a key. (To validate can also mean
to officially approve something; thus NIST validates cryptographic
modules for conformance with FIPS PUB 140-1.)
Rule 2: Use "verify" when referring to a process intended to test
or prove the truth or accuracy of a fact or value.
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The rationale for Rule is as follows: "Verify" derives from a word
that means "true" in Latin. thus, to verify means to prove the
truth of an assertion by examining evidence or performing tests.
To verify an identity, an authentication process must examine
identification information that is presented or generated. To
validate a certificate, a certificate user must verify the digital
signature on the certificate by performing calculations; must
verify that the current time is within the certificate's validity
period; and may need to validate a certification path involving
additional certificates.
validation
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.
value-added network (VAN)
(I) A computer network or subnetwork (which is usually a
commercial enterprise) that transmits, receives, and stores EDI
transactions on behalf of its customers.
(C) A VAN may also provide additional services, ranging from EDI
format translation, to EDI-to-FAX conversion, to integrated
business systems.
VAN
See: value-added network.
verification
1. System verification: The process of comparing two levels of
system specification for proper correspondence, such as comparing
a security policy with a top-level specification, a top-level
specification with source code, or source code with object code.
[NCS04]
2. Identification verification: Presenting information to
establish the truth of a claimed identity.
verify
See: validate vs. verify.
violation
See: security violation.
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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 (such as the
Internet), often by using encryption (located at hosts or
gateways), and often by tunneling links of the virtual network
across the real network.
(C) 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 using encrypted tunnels to
connect from firewall to firewall across the Internet and not
allowing any other traffic through the firewalls. 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 real network.
virus
(I) A hidden, self-replicating 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 it active.
VPN
See: virtual private network.
vulnerability
(I) A flaw or weakness in a system's design, implementation, or
operation that could be exploited to violate the system's security
policy.
(C) Most systems have vulnerabilities of some sort, 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 benefit for someone to make an attack.
W3
See: World Wide Web.
war dialer
(I) A computer program that automatically dials a series of
telephone numbers to find lines connected to computer systems, and
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catalogs those numbers so that a cracker can try to break into the
systems.
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, thus preventing destabilizing accumulations. (Also see:
International Traffic in Arms Regulations.)
(C) The Arrangement began operations in September 1996. The
participating countries are 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. Participants meet on a regular basis in Vienna,
where the Arrangement has a headquarters
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 will be in
accordance with national legislation and policies and will be
implemented on the basis of national discretion.
watermarking
See: digital watermarking.
web vs. Web
1. (I) Capitalized: Internet Standards Process documents SHOULD
capitalize "the Web" when using the term (usually as a noun) to
refer specifically to the World Wide Web. (Similarly, see:
internet vs. Internet.)
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2. (C) Not capitalized: Internet Standards Process document 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.
(C) IETF documents SHOULD spell out "World Wide Web" fully at the
first instance of usage and SHOULD Use "Web" and "web" especially
carefully where confusion with the PGP web of trust is possible.
web of trust
(O) PGP usage: A trust-file PKI technique used in PGP for building
a file of validated public keys by making personal judgments about
being able to trust certain people to be holding properly
certified keys of other people. (Compare with: certification
hierarchy, mesh PKI.)
web server
(I) A software process that runs on a host computer connected to
the Internet to respond to HTTP requests for documents from client
web browsers.
wiretapping
(I) An attack that intercepts and accesses data flowing between
two points in a communication system.
(C) Although the term originally referred to making a mechanical
connection to an electrical conductor, it is now used to refer to
reading information from any sort of medium used for a link, or
even from a gateway or a subnetwork switch.)
(C) "Active wiretapping" (see: active attack) attempts to alter
the data or otherwise affect the flow; "passive wiretapping" (see:
passive attack) only attempts to observe and gain knowledge of the
data. (Also see: end-to-end encryption.)
work factor
(I) General security usage: 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.
(I) Cryptography usage: The estimated amount of computing time and
power needed to break a cryptographic system.
World Wide Web ("the Web", WWW, W3)
(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. (Also see: web vs. Web.)
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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 computer resources destructively. (Also see:
Morris Worm, virus.)
wrap
(C) To use cryptography to provide data confidentiality service
for a data set. (Also see: encrypt, seal.) Internet Standards
Process documents SHOULD NOT use this term because it duplicates
the meaning of a standard term. Instead, use "encrypt" or use a
term that is specific to the mechanism used.
WWW
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, X.500 Directory
(N) An ITU-T Recommendation [X500] that is one part of a joint
ITU-T/ISO multi-part standard 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.) (Also see: X.509.)
(C) 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 unique DN. An 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 an 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 is one part of a joint
ITU-T/ISO multi-part standard (see: X.500). X.509 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.) (Also see: X.500.)
(C) X.509 describes two levels of authentication: simple
authentication based on a password, and strong authentication
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based on a public-key certificate. (Also see: X.509 public-key
certificate.)
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.)
(C) 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.
(C) An X.509 attribute certificate contains a sequence of data
items and has a digital signature is computed on 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) Either an X.509 public-key certificate or an X.509 attribute
certificate.
(C) This glossary uses the term with the precise meaning
recommended here. However, some who use the term may not be aware
that X.509 specifies attribute certificates that do not contain a
public key. Even among those who are aware, this term is commonly
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used as an abbreviation to mean "X.509 public-key certificate".
Internet Standards Process documents MAY use the term as an
abbreviation for "X.509 public-key certificate", but only after
using the full term at the first instance. Internet Standards
Process documents SHOULD NOT use this term as an abbreviation to
mean "X.509 attribute 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.)
(C) Internet Standards Process documents SHOULD NOT refer to an
X.509 CRL as a digital certificate, but note that it does meet
this Glossary's definition of that term. 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 (see: certificate revocation).
(R) 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 may optionally contain items 1, 6b, 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..br
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.)
(C) 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.
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1. version Identifies v1, v2, or v3.
2. serialNumber Certificate serial number;
an integer assigned by the issuer.
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.
XTACACS
See: (secondary definition in) Terminal Access Controller (TAC)
Access Control System.
Yellow Book
(C) Internet Standards Process documents SHOULD NOT use this term
as a synonym for "Computer Security Requirements: Guidance for
Applying the Department of Defense Trusted Computer System
Evaluation Criteria in Specific Environments" [CSC3]. Instead, use
the full proper name of the document or, in subsequent references,
a conventional abbreviation. (See: (usage note under) Green Book,
Rainbow Series).
zeroize
(I) Use erasure or other means to render stored data--particularly
a key stored in a cryptographic module or other device--unusable
and unrecoverable.
(O) Erase electronically stored data by altering the contents of
the data storage so as to prevent the recovery of the data.
[FP140]
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4. References
[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: Minerva M. Yeung, "Digital
Watermarking"; Nasir Memom and Ping Wah Wong, "Protecting
Digital Media Content"; and Scott Craver, Boon-Lock Yeo, and
Minerva Yeung, "Technical Trials and Legal Tribulations".
[A3092] American National Standards Institute, "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.
[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.
[CIPSO] Trusted Systems Interoperability Working Group, "Common IP
Security Option", ver. 2.3, 9 Mar 1993.
[CSC1] [U.S.]Department of Defense 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
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Registering Computer Security Objects", National Institute
of Standards Interagency Report 5308, Dec 1993.
[DH76] W. Diffie and M. H. Hellman, "New Directions in Cryptography"
in "IEEE Transactions on Information Theory", vol. IT-22,
no. 6, Nov 1976, pp. 644-654.
[DOD1] U.S. Department of Defense, "Department of Defense Trusted
Computer System Evaluation Criteria", DoD 5200.28-STD, 26
Dec 1985. (Supersedes [CSC1].)
[DOD2] ---, Directive 5200.28, "Security Requirements for Automated
Information Systems (AISs)", 21 Mar 1988.
[DOD3] ---, "X.509 Certificate Policy", ver. 2, Mar 1999.
[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.
[FP039] U.S. Department of Commerce, "Glossary for Computer Systems
Security", Federal Information Processing Standards
Publication (FIPS PUB) 39, 15 Feb 1976.
[FP046] ---, "Data Encryption Standard (DES)", FIPS PUB 46-2, 30 Dec
1993.
[FP081] ---, "DES Modes of Operation", FIPS PUB 81, 2 Dec 1980.
[FP113] ---, "Computer Data Authentication", FIPS PUB 113, 30 May
1985.
[FP140] ---, "Security Requirements for Cryptographic Modules", FIPS
PUB 140-1, 11 Jan 1994.
[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 180-1, 17 Apr 1995.
[FP185] ---, "Escrowed Encryption Standard", FIPS PUB 185, 9 Feb
1994.
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[FP186] ---, "Digital Signature Standard (DSS)", FIPS PUB 186, 19 May
1994.
[FP188] ---, "Standard Security Label for Information Transfer", FIPS
PUB 188, 6 Sep 1994.
[FPKI] ---, "Public Key Infrastructure (PKI) Technical
Specifications: Part A--Technical Concept of Operations",
National Institute of Standards, 4 Sep 1998.
[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. (AKA ITU-T Recommendation X.200.)
---, "Information Processing Systems--Open Systems
Interconnection Reference Model--Basic Reference Model--Part
2: Security Architecture", ISO/IEC 7499-2.
---, "Information Processing Systems--Open Systems
Interconnection Mode--Basic Reference ModelQPart 4:
Management Framework", ISO/IEC 7498-4.
[I7812] ---, "Identification cards--Identification of issuers--Part
1: Numbering system, ISO/IEC 7812-1:1993, and Identification
cards--Identification of issuers--Part 2: Application and
registration procedures", ISO/IEC 7812-2:1993.
[I9945] "Portable Operating System Interface for Computer
Environments", ISO/IEC 9945-1: 1990.
[Kahn] David Kahn, "The Codebreakers: The Story of Secret Writing",
The Macmillan Company, New York, 1967.
[MISPC] U.S. Department of Commerce, "Minimum Interoperability
Specification for PKI Components (MISPC), Version 1",
National Institute of Standards Special Publication 800-15,
Sep 1997.
[NCS01] National Computer Security Center, "A Guide to Understanding
Audit in Trusted Systems", NCSC-TG-001, 1 Jun 1988. (Part of
the Rainbow Series.)
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[NCS04] ---, "Glossary of Computer Security Terms", NCSC-TG-004, ver.
1, 21 Oct 1988. (Part of the Rainbow Series.)
[NCS05] ---, "Trusted Network Interpretation of the Trusted Computer
System Evaluation Criteria", NCSC-TG-005, ver. 1, 31 Jul
1987. (Part of the Rainbow Series.)
[NCS25] ---, "A Guide to Understanding Data Remanence in Automated
Information Systems", NCSC-TG-025, ver. 2, Sep 1991. (Part
of the Rainbow Series.)
[PGP] Simson Garfinkel, "PGP: Pretty Good Privacy", O'Reilly &
Associates, Inc., Sebastopol, California, 1995.
[PKCS] Burton S. Kaliski, Jr., "An Overview of the PKCS Standards",
RSA Data Security, Inc., 3 Jun 1991.
[PKC07] RSA Laboratories, "PKCS #7: Cryptographic Message Syntax
Standard", Version 1.5, RSA Laboratories Technical Note, 1
Nov 1993.
[PKC10] ---, "PKCS #10: Certification Request Syntax Standard",
Version 1.0, RSA Laboratories Technical Note, 1 Nov 1993
[PKC11] ---, "PKCS #11: Cryptographic Token Interface Standard", ver.
1.0, 28 Apr 1995.
[R0768] J. Postel, "User Datagram Protocol", STD 6, RFC 768, 28 Aug
1980.
[R0791] ---, "Internet Protocol", STD 5, RFC 791, 1 Sep 1981.
[R0792] ---, "Internet Control Message Protocol", STD 5, RFC 792, Sep
1981.
[R0793] ---, ed., "Transmission Control Protocol", STD 7, RFC 793,
Sep 1981.
[R0821] ---, "Simple Mail Transfer Protocol", STD 10, RFC 821, Aug
1982.
[R0822] D. H. Crocker, "Standard for the Format of ARPA Internet Text
Messages", STD 11, RFC 822, 13 Aug 1982.
[R0854] J. Postel and J. Reynolds, "TELNET Protocol Specification",
STD 8, RFC 854, May 1983.
[R0959] ---, "File Transfer Protocol (FTP)", STD 9, RFC 959, Oct
1985.
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[R1034] P. Mockapetris, "Domain Names--Concepts and Facilities", STD
13, RFC 1034, Nov 1987.
[R1157] J. Case, M. Fedor, M. Schoffstall, and J. Davin, "A Simple
Network Management Protocol (SNMP)", STD 15, RFC 1157, May
1990.
[R1208] O. Jacobsen and D. Lynch, "A Glossary of Networking Terms",
RFC 1208, Mar 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, W. Simpson, "PPP Authentication Protocols", RFC
1334, Oct 1992.
[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.
[R1508] J. Linn, "Generic Security Service Application Program
Interface", RFC 1508, Sep 1993.
[R1510] J. Kohl and C. Neuman, "The Kerberos Network Authentication
Service (V5)", RFC 1510, Sep 1993
[R1591] ---, "Domain Name System Structure and Delegation", Mar 1994.
[R1630] T. Berners-Lee, "Universal Resource Identifiers in WWW", RFC
1630, June 1994.
[R1738] ---, L. Masinter, and M. McCahill, ed's., "Uniform Resource
Locators (URL)", RFC 1738, Dec 1994.
[R1750] D. Eastlake, 3rd, S. Crocker, and J. Schiller, "Randomness
Recommendations for Security", Dec 1994.
[R1777] W. Yeong, T. Howes, and S. Kille, "Lightweight Directory
Access Protocol", Mar 1995
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[R1808] R. Fielding, "Relative Uniform Resource Locators", RFC 1808,
Jun 1995
[R1848] S. Crocker, N. Freed, J. Galvin, and S. Murphy, "MIME Object
Security Services", RFC 1848, Oct 1995.
[R1851] P. Karn, P. Metzger, and W. Simpson, "The ESP Triple DES
Transform", RFC 1851, Sep 1995.
[R1866] T. Berners-Lee, "Hypertext Markup Language--2.0", RFC 1866,
Nov 1995.
[R1928] M. Leech, M. Ganis, Y. Lee, R. Kuris, D. Koblas, and L.
Jones, "SOCKS Protocol Version 5", RFC 1928, Mar 1996.
[R1938] N. Haller and C. Metzion, "A One-Time Password System", RFC
1938, May 1996.
[R1983] G. Malkin, ed., "Internet Users' Glossary", RFC 1983, FYI 18,
Aug 1996.
[R1994] W. Simpson, "PPP Challenge Handshake Authentication Protocol
(CHAP)", RFC 1994, Aug 1996.
[R2023] J. Postel and J. Reynolds, "Instructions to RFC Authors", RFC
2023, Oct 1997.
[R2026] S. Bradner, "The Internet Standards Process--Revision 3",
BCP009, RFC 2026, Mar 1994.
[R2045] N. Freed and N. Borenstein, "Multipurpose Internet Mail
Extensions (MIME) Part One: Format of Internet Message
Bodies", RFC 2045, Nov 1996.
[R2460] S. Deering, R. Hinden, "Internet Protocol, Version 6 (IPv6)
Specification", RFC 2460, Dec 1998.
[R2065] D. Eastlake, 3rd, "Domain Name System Security Extensions",
RFC 2065, Jan 1997.
[R2068] R. Fielding, J. Gettys, J. Mogul, H. Frystyk, T. Berners-Lee,
"Hypertext Transfer Protocol--HTTP/1.1", RFC 2068, Jan 1997.
[R2104] H. Krawczyk, M. Bellare, and R. Canetti, "HMAC: Keyed-Hashing
for Message Authentication", RFC 2104, Feb 1997.
[R2284] L. Blunk and J. Vollbrecht, "PPP Extensible Authentication
Protocol (EAP)", RFC 2284, Mar 1998.
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[R2315] B. Kaliski, "PKCS #7: Cryptographic Message Syntax, Version
1.5", RFC 2315, Mar 1998.
[R2373] R. Hinden and S. Deering, "IP Version 6 Addressing
Architecture", RFC 2373.
[R2401] S. Kent and R. Atkinson, "Security Architecture for the
Internet Protocol", RFC 2401, Nov 1998.
[R2402] S. Kent and R. Atkinson, "IP Authentication Header", RFC
2402, Nov 1998.
[R2406] S. Kent and R. Atkinson, "IP Encapsulating Security Payload
(ESP)", RFC 2406, Nov 1998.
[R2409] D. Harkins and D. Carrel, "The Internet Key Exchange (IKE)",
RFC 2409, Nov 1998.
[R2510] C. Adams and S. Farrell, "Internet X.509 Public Key
Infrastructure Certificate Management Protocols", RFC 2510,
Mar 1999.
[R2527] S. Chokhani and W. Ford, "Internet X.509 Public Key
Infrastructure, Certificate Policy and Certification
Practices Framework", RFC 2527, Mar 1999.
[R2570] J. Case, R. Mundy, D. Partain, B. Stewart, " Introduction to
Version 3 of the Internet-Standard Network Management
Framework", RFC 2570, Apr 1999.
[R2574] U. Blumenthal and B. Wijnen, "User-based Security Model (USM)
for Version 3 of the Simple Network Management Protocol
(SNMPv3)", RFC 2574, Apr 1999.
[R2631] E. Rescorla, "Diffie-Hellman Key Agreement Method", RFC 2631,
June 1999
[R2633] B. Ramsdell, ed., "S/MIME Version 3 Message Specification",
RFC 2633, June 1999
[R2634] P. Hoffman, ed., "Enhanced Security Services for S/MIME", RFC
2634, June 1999
[Schn] Bruce Schneier, "Applied Cryptography", John Wiley & Sons,
Inc., New York, 1994.
[SDNS3] National Security Agency, "Secure Data Network Systems,
Security Protocol 3 (SP3)", document SDN.301, Revision 1.5,
15 May 1989.
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[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 June
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.
[SET2] ---, "SET Secure Electronic Transaction Specification, Book
2: Programmer's Guide", ver. 1.0, 31 May 1997.
[Stei] J. Steiner, C. Neuman, and J. Schiller, "Kerberos: An
Authentication Service for Open Network Systems" in "Usenix
Conference Proceedings", Feb 1988.
[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". (AKA 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". (AKA ISO 9594-8.)
[X519] ---, Recommendation X.519, "Information Technology--Open
Systems Interconnection--The Directory: Protocol
Specifications".
[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. (AKA 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. (AKA ISO/IEC 8825-1.)
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5. Security Considerations
The focus of this document is security terminology, but this document
does not discuss security issues in the sense of describing or
analyzing threats to, vulnerabilities of, or countermeasures to
protect, any specific Internet Standard protocol.
6. Acknowledgments
Pat Cain, Mike Kong, and Charles Lynn provided meticulous comments on
an initial version of this document.
7. Author's Address
Please address all comments to:
Robert W. Shirey
Security Practice Center
GTE Internetworking, Mail Stop 30/12B2
1300 Seventeenth Street North, Suite 1200
Arlington, VA 22209-3801 USA
Phone: +1 (703) 284-4641
Fax: +1 (703) 284-2766
Email: rshirey@bbn.com
8. Expiration Date
This Internet Draft expires on 3 February 2000.
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