Internet Draft ETSI TC-SEC (ETSI)
S/MIME Working Group J Ross (Security & Standards)
expires in six months D Pinkas (Bull)
Target Category: Informational N Pope (Security & Standards)
March 2000
Electronic Signature Formats
for long term electronic signature
<draft-ietf-smime-esformats-00.txt>
Status of this Memo
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Abstract
The informational RFC defines the format of an electronic signature
that can remain valid over long periods. This includes evidence as to
its validity even if the signer or verifying party later attempts to
deny (repudiates) the validity of the signature.
The contents of this Informational RFC is technically equivalent to
ETSI ES 201 733 V.1.1.1 Copyright (C). Individual copies of this
ETSI deliverable can be downloaded from http://www.etsi.org
1. Introduction
This document is intended to cover electronic signatures for various
types of transactions, including business transactions (e.g. purchase
requisition, contract, and invoice applications) where long term
validity of such signatures is important. Electronic signatures can
be used for any transaction between an individual and a company,
between two companies, between an individual and a governmental body,
etc. This document is independent of any environment. It can be applied
to any environment e.g. smart cards, GSM SIM cards, special programs
for electronic signatures etc.
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An electronic signature produced in accordance with this document
provides evidence that can be processed to get confidence that some
commitment has been explicitly endorsed under a Signature policy, at a
given time, by a signer under an identifier, e.g. a name or a
pseudonym, and optionally a role.
The European Directive on a community framework for Electronic
Signatures defines an electronic signature as: "data in electronic form
which is attached to or logically associated with other electronic data
and which serves as a method of authentication". An electronic
signature as used in the current document is a form of advanced
electronic signature as defined in the Directive.
The key words "MUST", "MUST NOT", "REQUIRED", "SHOULD", "SHOULD NOT",
"RECOMMENDED", "MAY", and "OPTIONAL" in this document (in uppercase,
as shown) are to be interpreted as described in [RFC2119].
2 Overview
2.1 Aim
The aim of this document is to define an Electronic Signature (ES) that
remains valid over long periods. This includes evidence as to its
validity even if the signer or verifying party later attempts to deny
(repudiates) the validity of the signature.
A signer is the entity that creates an electronic signature.
This document specifies use of trusted service providers (e.g.
TimeStamping Authorities (TSA)), and the data that needs to be archived
(e.g. cross certificates and revocation lists) to meet the requirements
of long term electronic signatures. An electronic signature defined by
this document can be used for arbitration in case of a dispute between
the signer and verifier, which may occur at some later time, even years
later. This document uses a signature policy, referenced by the signer,
as the basis for establishing the validity of an electronic signature.
A Trusted Service Provider (TSP) is an entity that helps to build trust
relationships by making available or providing some information upon
request.
A verifier is an entity that verifies an evidence. (ISO/IEC 13888-1
[13]). Within the context of this document this is an entity that
validates an electronic signature.
A signature policy is a set of rules for the creation and validation of
an electronic signature, under which the signature can be determined to
be valid
2.2 Basis of Present Document
This document is based on the use of public key cryptography to produce
digital signatures, supported by public key certificates.
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A Public key certificate is a public keys of a user, together with some
other information, rendered unforgeable by encipherment with the
private key of the Certification Authority (CA) which issued it (ITU-T
Recommendation X.509 [1]).
This document also uses timestamping services to prove the validity of
a signature long after the normal lifetime of critical elements of an
electronic signature and to support non-repudiation. It also, as an
option, uses additional timestamps to provide very long-term protection
against key compromise or weakened algorithms.
This document builds on existing standards that are widely adopted.
This includes:
* RFC 2630 [9] Crytographic Message Syntax (CMS);
* ITU-T Recommendation X.509 [1] Authentication framework;
* RFC 2459 [7] Internet X.509 Public Key Infrastructure (PKIX)
Certificate and CRL Profile;
* RFC (to be published) PKIX Timestamping protocol.
NOTE: See clause 2 for a full set of references.
2.3 Major Parties
The following are the major parties involved in a business transaction
supported by electronic signatures as defined in this document:
* the Signer;
* the Verifier;
* Trusted Service Providers (TSP);
* the Arbitrator.
The arbitrator is an entity that may be used to arbitrate a dispute
between a signer and verifier when there is a disagreement on the
validity of a digital signature.
The Signer is the entity that creates the electronic signature. When
the signer digitally signs over data using the prescribed format, this
represents a commitment on behalf of the signing entity to the data
being signed.
The Verifier is the entity that validates the electronic signature, it
may be a single entity or multiple entities.
The Trusted Service Providers (TSPs) are one or more entities that help
to build trust relationships between the signer and verifier. They
support the signer and verifier by means of supporting services
including: user certificates, cross-certificates, timestamping tokens,
CRLs, ARLs, OCSP responses.
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The following TSPs are used to support the
functions defined in this document:
* Certification Authorities;
* Registration Authorities;
* Repository Authorities (e.g. a Directory);
* TimeStamping Authorities;
* Signature Policy Issuers.
Certification Authorities provide users with public key certificates.
Registration Authorities allows the registration of entities before a
CA generates certificates.
Repository Authorities publish CRLs issued by CAs, signature policies
issued by Signature Policy Issuers and optionally public key
certificates.
TimeStamping Authorities attest that some data was formed before a
given trusted time.
Signature Policy Issuers define the technical and procedural
requirements for electronic signature creation and validation, in order
to meet a particular business need.
In some cases the following additional TSPs are needed:
* Attribute Authorities.
Attributes Authorities provide users with attributes linked to public
key certificates
An Arbitrator is an entity that arbitrates disputes between a signer
and a verifier.
A signature policy issuer is an entity that defines the technical and
procedural requirements for electronic signature creation and
validation, in order to meet a particular business need
2.4 Electronic Signatures and Validation Data
Validation of an electronic signature in accordance with this document
requires:
* The electronic signature; this includes:
- the signature policy;
- the signed user data;
- the digital signature;
- other signed attributes provided by the signer.
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* Validation data which is the additional data needed to validate
the electronic signature; this includes:
- certificates;
- revocation status information,
- trusted time-stamps from Trusted Service Providers (TSPs).
* The signature policy specifies the technical requirements on
signature creation and validation in order to meet a particular
business need. A given legal/contractual context may recognize a
particular signature policy as meeting its requirements.
For example: a specific signature policy may be recognized by court of
law as meeting the requirements of the European Directive for electronic
commerce. A signature policy may be written using a formal notation like
ASN.1 (see 6.1) or in an informal free text form provided the rules of
the policy are clearly identified. However, for a given signature policy
there shall be one definitive form which has a unique binary encoded
value.
Signed user data is the user's data that is signed.
The Digital Signature is the digital signature applied over the
following attributes provided by the signer:
* hash of the user data;
* signature Policy Identifier;
* other signed attributes
The other signed attributes include any additional information which
must be signed to conform to the signature policy or this document
(e.g. signing time).
The Validation Data may be collected by the signer and/or the verifier
and must meet the requirements of the signature policy. Additional
data includes CA certificates as well as revocation status information
in the form of Certificate Revocation Lists (CRLs) or certificate
status information provided by an on-line service. Additional data
also includes timestamps and other time related data used to provide
evidence of the timing of given events. It is required, as a minimum,
that either the signer or verifier obtains a timestamp over the
signer's signature.
A Certificate Revocation List (CRL) is signed list indicating a set of
certificates that are no longer considered valid by the certificate
issuer [X.509 FPAM]digital signature: 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 (ISO 7498-2 [12])
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2.5 Forms of Validation Data
An electronic signature may exist in many forms including:
* the Electronic Signature (ES), which includes the digital
signature and other basic information provided by the signer;
* the ES with Timestamp (ES-T), which adds a timestamp to the
Electronic Signature, to take initial steps towards providing
long term validity;
* the ES with Complete validation data (ES-C), which adds to the
ES-T references to the complete set of data supporting the
validity of the electronic signature (i.e. revocation status
information).
The signer must provide at least the ES form, but in some cases may
decide to provide the ES-T form and in the extreme case could provide
the ES-C form. If the signer does not provide ES-T, the verifier must
create the ES-T on first receipt of an electronic signature. The ES-T
provides independent evidence of the existence of the signature at the
time it was first verified which should be near the time it was
created, and so protects against later repudiation of the existence of
the signature. If the signer does not provide ES-C the verifier must
create the ES-C when the complete set of revocation and other validation
data is available.
The ES satisfies the legal requirements for electronic signatures as
defined in the European Directive on electronic signatures, see Annex C
for further discussion on relationship of this document to the
Directive. It provides basic authentication and integrity protection
and can be created without accessing on-line (timestamping) services.
However, without the addition of a timestamp the electronic signature
does not protect against the threat that the signer later denies having
created the electronic signature (i.e. does not provide non-repudiation
of its existence).
The ES-T time-stamp should be created close to the time that ES was
created to provide maximum protection against repudiation. At this time
ll the data needed to complete the validation may not be available but
what information is readily available may be used to carry out some of
the initial checks. For example, only part of the revocation
information may be available for verification at that point in time.
Generally, the ES-C form cannot be created at the same time as the ES,
as it is necessary to allow time for any revocation information to be
captured. Also, if a certificate is found to be temporarily suspended,
it will be necessary to wait until the end of the suspension period.
The signer should only create the ES-C in situations where it was
prepared to wait for a sufficient length of time after creating the ES
form before dispatching the ES-C. This, however, has the advantage that
the verifier can be presented with the complete set of data supporting
the validity of the ES.
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Support for ES-C by the verifier is mandated (see clause 14 for
specific conformance requirements).
An Electronic Signature (ES), with the additional validation data forming the
ES-T and ES-C is illustrated in Figure 1:
+------------------------------------------------------------ES-C-----+
|+--------------------------------------------ES-T-----+ |
||+------Elect.Signature (ES)----------+ +------------+| +-----------+|
|||+---------+ +----------+ +---------+| |Timestamp || |Complete ||
||||Signature| | Other | | Digital || |over digital|| |certificate||
||||Policy ID| | Signed | |Signature|| |signature || |and ||
|||| | |Attributes| | || +------------+| |revocation ||
|||+---------+ +----------+ +---------+| | |references ||
||+------------------------------------+ | +-----------+|
|+-----------------------------------------------------+ |
+---------------------------------------------------------------------+
Figure 1: Illustration of an ES, ES-T and ES-C
2.6 Extended Forms of Validation Data
The complete validation data (ES-C) described above may be extended to
form an ES with eXtended validation data (ES-X) to meet following
additional requirements.
Firstly, when the verifier does not has access to,
* the signer's certificate,
* all the CA certificates that make up the full certification
path,
* all the associated revocation status information, as referenced
in the ES-C.
then the values of these certificates and revocation information may be
added to the ES-C. This form of extended validation data is called a
X-Long.
Secondly, if there is a risk that any CA keys used in the certificate
chain may be compromised, then it is necessary to additionally
timestamp the validation data by either:
* timestamping all the validation data as held with the ES(ES-C),
this eXtended validation data is called a Type 1 X-Timestamp; or
* timestamping individual reference data as used for complete
validation.
This form of eXtended validation data is called a Type 2 X-Timestamp.
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NOTE: The advantages/drawbacks for Type 1 and Type 2 X-Timestamp are
discussed in this document (see clause 4.4.6.)
If all the above conditions occur then a combination of the two formats
above may be used. This form of eXtended validation data is called
a X-Long-Timestamped.
Support for the extended forms of validation data is optional.
An Electronic Signature (ES) , with the additional validation data
forming the ES-X long is illustrated in Figure 2:
+------------------------------------------------------- ES-X Long--+
|+--------------------------------------- EC-C --------+ |
||+---- Elect.Signature (ES)----+ +--------+| +--------+ |
|||+-------+-+-------+-+-------+| +---------+|Complete|| |Complete| |
||||Signa- | |Other | |Digital|| |Timestamp||certi- || |certi- | |
||||ture | |Signed | |Signa- || |over ||ficate || |ficate | |
||||Policy | |Attri- | |ture || |digital ||and || |and | |
||||ID | |butes | | || |signature||revoc. || |revoc. | |
|||+-------+ +-------+ +-------+| +---------+|refs || |data | |
||+-----------------------------+ +--------+| +--------+ |
|+-----------------------------------------------------+ |
+-------------------------------------------------------------------+
Figure 2: Illustration of an ES and ES-X long.
An Electronic Signature (ES) , with the additional validation data
forming the eXtended Validation Data - Type 1 is illustrated in
Figure 3:
+---------------------------------------------------------- ES-X 1 -+
|+---------------------------------------- EC-C --------+ |
|| +---- Elect.Signature (ES)----+ +--------+| +-------+ |
|| |+-------+ +-------+ +-------+| +---------+|Complete|| | | |
|| ||Signa- | |Other | |Digital|| |Timestamp||certifi-|| | Time- | |
|| ||ture | |Signed | |Signa- || |over ||cate and|| | stamp | |
|| ||Policy | |Attri- | |ture || |digital ||revoc. || | over | |
|| ||ID | |butes | | || |signature||refs || | CES | |
|| |+-------+ +-------+ +-------+| +---------+| || | | |
|| +-----------------------------+ +--------+| +-------+ |
|+------------------------------------------------------+ |
+-------------------------------------------------------------------+
Figure 3: Illustration of ES with ES-X Type 1
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An Electronic Signature (ES) , with the additional validation data
forming the eXtended Validation Data - Type 2 is illustrated in
Figure 4:
+-------------------------------------------------------- ES-X 2 ---+
|+--------------------------------------- EC-C --------+ |
||+---- Elect.Signature (ES)----+ +--------+| +--------+ |
|||+-------+ +-------+ +-------+| +---------+|Complete|| |Times | |
||||Signa- | |Other | |Digital|| |Timestamp||certs || |Stamp | |
||||ture | |Signed | |Signa- || |over ||and || |over | |
||||Policy | |Attri- | |ture || |digital ||revoc. || |Complete| |
||||ID | |butes | | || |signature||refs || |certs | |
|||+-------+ +-------+ +-------+| +---------+| || |and | |
||+-----------------------------+ +--------+| |revoc. | |
|| | |refs | |
|+-----------------------------------------------------+ +--------+ |
+-------------------------------------------------------------------+
Figure 4: Illustration of ES with ES-X Type 2
2.7 Archive Validation Data
Before the algorithms, keys and other cryptographic data used at the
time the ES-C was built become weak and the cryptographic functions
become vulnerable, or the certificates supporting previous timestamps
expires, the signed data, the ES-C and any additional information
(ES-X) should be timestamped. If possible this should use stronger
algorithms (or longer key lengths) than in the original timestamp.
This additional data and timestamp is called Archive Validation Data
(ES-A). The Timestamping process may be repeated every time the
protection used to timestamp a previous ES-A become weak. An ES-A
may thus bear multiple embedded time stamps.
Support for ES-A is optional.
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An example of an Electronic Signature (ES), with the additional
validation data for the ES-C and ES-X forming the ES-A is illustrated
in Figure 5.
+-------------------------------- ES-A --------- ----------+
| +-------------------- ES-A -----------------+ |
| | +--------- ES-X -------------- + | |
| | |..............................| +-----+ | +-----+ |
| | |..............................| |Time | | |Time | |
| | |..............................| |Stamp| | |Stamp| |
| | | | +-----+ | +-----+ |
| | +----------------------------- + | |
| +-------------------------------------------+ |
+----------------------------------------------------------+
Figure 5: Illustration of ES -A
2.8 Arbitration
The ES-C may be used for arbitration should there be a dispute between
the signer and verifier, provided that:
* the arbitrator knows where to retrieve the signer's certificate
(if not already present), all the cross-certificates and the
required CRLs and/or OCSPs responses referenced in the ES-C;
* none of the issuing key from the certificate chain have ever
been compromised;
* the cryptography used at the time the ES-C was built has not
been broken at the time the arbitration is performed.
When the first condition is not met, then the plaintiff must provide
an ES-X Long.
When it is known by some external means that the second condition is
not met, then the plaintiff must provide an ES-X Timestamped.
When the two previous conditions are not met, the plaintiff must
provide the two above information (i.e. an ES-X Timestamped and Long).
When the last condition is not met, the plaintiff must provide an ES-
A.
It should be noticed that a verifier may need to get two time stamps at
two different instants of time: one soon after the generation of the ES
and one soon after some grace period allowing any entity from the
certification chain to declare a key compromise.
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2.9 Validation Process
The Validation Process validates an electronic signature in accordance
with the requirements of the signature policy. The output status of the
validation process can be:
* valid;
* invalid;
... * incomplete verification.
A Valid response indicates that the signature has passed verification
and it complies with the signature validation policy.
A signature validation policy is a part of the signature policy which
specifies the technical requirements on the signer in creating a
signature and verifier when validating a signature
An Invalid response indicates that either the signature format is
incorrect or that the digital signature value fails verification
(e.g. the integrity checks on the digital signature value fails or any
of the certificates on which the digital signature verification depends
is known to be invalid or revoked).
An Incomplete Validation response indicates that the format and digital
signature verifications have not failed but there is insufficient
information to determine if the electronic signature is valid under the
signature policy.
This can include situations where additional information, which does
not effect the validity of the digital signature value, may be
available but is invalid. In the case of Incomplete Validation, it may
be possible to request that the electronic signature be checked again
at a later date when additional validation information might become
available. Also, in the case of incomplete validation, additional
information may be made available to the application or user, thus
allowing the application or user to decide what to do with partially
correct electronic signatures.
The validation process may also output validation data :
* a signature timestamp;
* the complete validation data;
* the archive validation data.
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2.10 Example Validation Sequence
As described earlier the signer or verifier may collect all the
additional data that forms the Electronic Signature. Figure 6, and
subsequent description, describes how the validation process may build
up a complete electronic signature over time.
+---------------------------------------- ES-C ----------+
|+----------------------------- ES-T -------+ |
||+--- Elect.Signature (ES) ----+ | +--------+ |
|||+-------+ +-------+ +-------+|+---------+| |Complete| |
||||Signa- | |Other | |Digital|||Timestamp|| |certifi-| |
||||ture | |Signed | |Signa- |||over || |cate and| |
||||Policy | |Attri- | |ture |||digital || |revoca- | |
||||ID | |butes | | |||signature|| |tion | |
|||+-------+ +-------+ +-------+|+---------+| |referen-| |
||+------------\----------------+ ^ | |ces | |
|| \ | | +--------+ |
|| \ 1 / | ^ |
|+----------------\----------------/--------+ | |
+------------------\--------------/-------------- /------+
\ /2 ----3-----/
+----------+ | / /
| Signed |\ v / |
|User data | \ +--------------------+ +------------+
+----------+ \--->| Validation Process |---> |- Valid |
+---|--^-------|--^--+ 4 |- Invalid |
| | | | |- Validation|
v | v | | Incomplete|
+---------+ +--------+ +------------+
|Signature| |Trusted |
| Policy | |Service |
| Issuer | |Provider|
+---------+ +--------+
Figure 6: Illustration of an ES with Complete validation data (ES-C)
Soon after receiving the electronic signature (ES) from the signer (1),
the digital signature value may be checked, the validation process
must at least add a time-stamp (2), unless the signer has provided one
which is trusted by the verifier. The validation process may also
validate the electronic signature, as required under the identified
signature policy, using additional data (e.g. certificates, CRL, etc.)
provided by trusted service providers. If the validation process is not
complete then the output from this stage is the ES-T.
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When all the additional data (e.g. the complete certificate and
revocation information) necessary to validate the electronic signature
first becomes available, then the validation process:
* obtains all the necessary additional certificate and revocation
status information;
* completes all the validation checks on the ES, using the
complete certificate and revocation information (if a timestamp
is not already present, this may be added at the same stage
combining ES-T and ES-C process);
* records the complete certificate and revocation references (3);
* indicates the validity status to the user (4).
At the same time as the validation process creates the ES-C, the
validation process may provide and/or record the values of certificates
and revocation status information used in ES-C, called the ES-X Long
(5). This is illustrated in figure 7:
+---------------------------------------------------- ES-X ---------+
|+--------------------------------------- ES-C --------+ +--------+ |
||+--- Elect.Signature (ES) ----+ +--------+ | |Complete| |
|||+-------+ +-------+ +-------+|+---------+|Complete| | |certifi-| |
||||Signa- | |Other | |Digital|||Timestamp||certifi-| | |cate | |
||||ture | |Signed | |Signa- |||over ||cate and| | |and | |
||||Policy | |Attri- | |ture |||digital ||revoca- | | |revoca- | |
||||ID | |butes | | |||signature||tion | | |tion | |
|||+-------+ +---|---+ +-------+|+---------+|referen-| | |Data | |
||+--------------\--------------+ ^ |ces | | +--------+ |
|| \ | +--------+ | ^ |
|| \ 1 2/ ^ | | |
|+------------------\--------------/-----------|-------+ / |
+--------------------\------------/-----------/-------------/-------+
\ / ---3---/ /
+----------+ | / / -----------5-----/
| Signed |\ v | | /
|User data | \ +--------------------+ +-----------+
+----------+ \--->| Validation Process |---> | - Valid |
+---|--^-------|--^--+ 4 | - Invalid |
| | | | +-----------+
v | v |
+---------+ +--------+
|Signature| |Trusted |
| Policy | |Service |
| Issuer | |Provider|
+---------+ +--------+
Figure 7: Illustration ES with eXtended validation data (Long)
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When the validation process creates the ES-C it may also create
extended forms of validation data. A first alternative is to timestamp
all data forming the Type 1 X-Timestamp (6). This is illustrated in
figure 8:
+---------------------------------------------------- ES-X -------+
|+--------------------------------------- ES-C --------+ +------+ |
||+--- Elect.Signature (ES) ----+ +--------+ | |Time- | |
|||+-------+ +-------+ +-------+|+---------+|Complete| | |stamp | |
||||Signa- | |Other | |Digital|||Timestamp||certifi-| | |over | |
||||ture | |Signed | |Signa- |||over ||cate and| | |CES | |
||||Policy | |Attri- | |ture |||digital ||revoca- | | +------+ |
||||ID | |butes | | |||signature||tion | | ^ |
|||+-------+ +--|----+ +-------+|+---------+|referen-| | | |
||+-------------|---------------+ ^ |ces | | | |
|| | | +--------+ | | |
|| \ 1 2/ ^ | | |
|+----------------\------------------/---------|-------+ | |
+------------------\----------------/----------/-------------/----+
\ / ----3--/ /
+----------+ | / / --------------6---/
| Signed |\ v | | /
|User data | \ +--------------------+ +-----------+
+----------+ \--->| Validation Process |---> | - Valid |
+---|--^-------|--^--+ 4 | - Invalid |
| | | | +-----------+
v | v |
+---------+ +--------+
|Signature| |Trusted |
| Policy | |Service |
| Issuer | |Provider|
+---------+ +--------+
Figure 8: Illustration of ES with eXtended validation data - Type 1 X-
Timestamp
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Another alternative is to timestamp the certificate and revocation
information references used to validate the electronic signature (but
not the signature) (6'); this is called Type 2 X-Timestamped. This is
illustrated in figure 9:
+---------------------------------------------------- ES-X ----------+
|+--------------------------------------- ES-C --------+ +---------+ |
||+--- Elect.Signature (ES) ----+ +--------+ | |Timestamp| |
|||+-------+ +-------+ +-------+|+---------+|Complete| | |over | |
||||Signa- | |Other | |Digital|||Timestamp||certifi-| | |Complete | |
||||ture | |Signed | |Signa- |||over ||cate and| | |Certifi- | |
||||Policy | |Attri- | |ture |||digital ||revoc. | | |cate and | |
||||ID | |butes | | |||signature||refs | | |revoc. | |
|||+-------+ +---^---+ +-------+|+----^----++---^----+ | |refs | |
||+--------------\--------------+ | | | +---------+ |
|+----------------\------------------/----------|------+ ^ |
+----------------1-\----------------/----------/--------------|------+
\ / -----3--/ |
+----------+ | 2/ / --------------6'-----/
| Signed |\ v | | /
|User data | \ +--------------------+ +-----------+
+----------+ \--->| Validation Process |---> | - Valid |
+---|--^-------|--^--+ 4 | - Invalid |
| | | | +-----------+
v | v |
+---------+ +--------+
|Signature| |Trusted |
| Policy | |Service |
| Issuer | |Provider|
+---------+ +--------+
Figure 9: Illustration of ES with eXtended validation data - Type 2 X-
Timestamp
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Before the algorithms used in any of electronic signatures become or
are likely, to be compromised or rendered vulnerable in the future, it
is necessary to timestamp the entire electronic signature, including
all the values of the validation and user data as an ES with Archive
validation data (ES-A)
An ES-A is illustrated in figure 10:
-------------------------------------------- ES-A --------------------+
----------------------------------------------------------------+ |
+------------------------------- EC-C --------++-----+ | |
| ||Time-| | |
|+-- Elect.Signature (ES) -+ +--------+||stamp| +-------+ |
||+------++-------++-------|+------+|Complete|||over | Complete| |
|||Signa-||Other ||Digital||Time- ||certifi-|||CES | |certi- |+----|
|||ture ||Signed ||Signa- ||stamp ||cate and||+-----+ |ficate |Arch-|
|||Policy||Attri- ||ture ||over ||revoca- ||+------+ |and |ive |
|||ID ||butes || ||digit.||tion |||Time- | |revoca-|Time |
||+------++---|---++-------||signa-||referen-|||stamp-| |tion |stamp|
|+------------|------------+|ture ||ces |||over | |data |+----|
| | +------++--------+|Complete\+-------+ ^ |
| | ^ ^ ||cert. | | | |
+-------------|----------------|---------|----+|and rev| | | |
\ | / |refs. | | | |
\ | / +-------+ | | |
-----------------\-------------|-------/------------------------+ | |
+----------+ \ | / / |
| Signed | \2 |3 / /--------------7-------/ |
|User data | \ | | / |
+-------\--+ \ | | / |
---------\------------|--------|----|---/-----------------------------+
\ v | | |
1\ +--------------------+ +-----------+
\------>| Validation Process |---> | - Valid |
+---|--^-------|--^--+ 4 | - Invalid |
| | | | +-----------+
v | v |
+---------+ +--------+
|Signature| |Trusted |
| Policy | |Service |
| Issuer | |Provider|
+---------+ +--------+
Figure 10: Illustration of an ES with Archive validation data (ES-A)
2.11 Additional optional features
This document also defines additional optional features to:
* indicate a commitment type being made by the signer;
* indicate the role under which a signature was created;
* support multiple signatures.
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3. Data structure of an Electronic Signature
This clause uses and builds upon the Crypographic Message Syntax (CMS),
as defined in RFC 2630, REF [CMS] , and Enhanced Security Services
(ESS), as defined in RFC 2634 [10], REF [ESS] . The overall structure
of Electronic Signature is as defined in [CMS]. The Electronic
Signature (ES) uses attributes defined in [CMS], [ESS] and
this document. This document defines in full the ES attributes which it
uses and are not defined elsewhere.
The mandated set of attributes and the digital signature value is
defined as the minimum Electronic Signature (ES) required by this
document. A signature policy MAY mandate other signed attributes are
present.
3.1 General Syntax
The general syntax of the ES is as defined in [CMS].
3.2 Data Content Type
The data content type of the ES is as defined in [CMS].
3.3 Signed-data Content Type
The Signed-data content type of the ES is as defined in [CMS].
To make sure that the verifier uses the right signers key, this
document mandates that the hash of the signers certificate is always
included in the Signing Certificate signed attribute.
3.4 SignedData Type
The syntax of the SignedData type of the ES is as defined in [CMS].
The fields of type SignedData have the meanings defined [CMS] except
that:
* version is the syntax version number. The value of version must
be 3.
* The identification of signer's certificate used to create the
signature is always signed. The validation policy may specify
requirements for the presence of certain certificates.
* The degenerate case where there are no signers is not valid in
this document.
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3.5 EncapsulatedContentInfo Type
The syntax of the EncapsulatedContentInfo a type of the ES is as defined
in [CMS].
For the purpose of long term validation as defined by this document, it
is advisable that either the eContent is present, or the data which is
signed is archived in such as way as to preserve the any data encoding.
It is important that the OCTET STRING used to generate the signature
remains the same every time either the verifier or an arbitrator
validates the signature.
The degenerate case where there are no signers is not valid in this
document.
3.6 SignerInfo Type
The syntax of the SignerInfo a type of the ES is as defined in [CMS].
Per-signer information is represented in the type SignerInfo. In the
case of multiple independent signatures, there is an instance
of this field for each signer.
The fields of type SignerInfo have the meanings defined in [CMS} except
that:
signedAttributes must, as a minimum,
contain the following attributes:
* ContentType as defined in clause 3.7.1.
* MessageDigest as defined in clause 3.7.2.
* SigningTime as defined in clause 3.7.3.
* SigningCertificate as defined in clause 3.8.1.
* SignaturePolicyId as defined in clause 3.9.1.
3.6.1 Message Digest Calculation Process
The message digest calculation process is as defined in [CMS].
3.6.2 Message Signature Generation Process
The input to the digital signature generation process is as defined in
[CMS].
3.6.3 Message Signature Verification Process
The procedures for CMS signed data validation are as defined in
[CMS] and enhanced in this document.
The input to the signature verification process includes the signer's
public key verified as correct using the ESS Signing Certificate or
Other Signing Certificate attribute.
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3.7 CMS Imported Mandatory Present Attributes
The following attributes MUST be present with the signed-data defined
by this document. The attributes are defined in [CMS].
3.7.1 Content Type
The syntax of the content-type attribute type of the ES is as defined
in [CMS].
3.7.2 Message Digest
The syntax of the message-digest attribute type of the ES is as defined
in [CMS].
3.7.3 Signing Time
The syntax of the message-digest attribute type of the ES is as defined
in [CMS]and further qualified by this document.
The signing-time attribute type specifies the time at which the signer
claims to have performed the signing process.
This present document recommends the use of GeneralizedTime.
3.8 Alternative Signing Certificate Attributes
One, and only one, of the following two alternative attributes MUST be
present with the signed-data defined by this document to identify the
signing certificate. Both attributes include an identifier and a hash
of the signing certificate. The first, which is adopted in existing
standards, may be used if with the SHA-1 hashing algorithm. The other
hall be used for other hashing algorithms are to be supported.
The signing certificate attribute is designed to prevent the simple
substitution and re-issue attacks, and to allow for a restricted set of
authorization certificates to be used in verifying a signature.
3.8.1 ESS Signing Certificate Attribute Definition
The syntax of the signing certificate attribute type of the ES is as
defined in [ESS], and further qualified and profile in this document.
The ESS signing certificate attribute must be a signed attribute.
This document mandates the presence of this attribute as a signed CMS
attribute, and the sequence must not be empty. The certificate used to
verify the signature must be identified in the sequence, the Signature
Validation Policy may mandate other certificates be present, that may
include all the certificates up to the point of trust. The encoding of
the ESSCertID for this certificate must include the issuerSerial
field.
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The issuerAndSerialNumber present in the SignerInfo must be
consistent with issuerSerial field. The certificate identified must be
used during the signature verification process. If the hash of the
certificate does not match the certificate used to verify the
signature, the signature must be considered invalid.
The sequence of policy information field is not used in this document.
NOTE: Where an attribute certificate is used by the signer to associate
a role, or other attributes of the signer, with the electronic
signature this is placed in the Signer Attribute attribute as defined
in clause 3.12.3.
3.8.2 Other Signing Certificate Attribute Definition
The following attribute is identical to the ESS SigningCertificate
defined above except that this attribute can be used with hashing
algorithms other than SHA-1.
This attribute must be used in the same manner as defined above for
the ESS SigningCertificate attribute.
The following object identifier identifies the signing certificate
attribute:
id-aa-ets-otherSigCert OBJECT IDENTIFIER ::= { iso(1)
member-body(2) us(840) rsadsi(113549) pkcs(1) pkcs9(9)
smime(16) id-aa(2) 19 }
The signing certificate attribute value has the ASN.1 syntax
OtherSigningCertificate
OtherSigningCertificate ::= SEQUENCE {
certs SEQUENCE OF OtherCertID,
policies SEQUENCE OF PolicyInformation OPTIONAL
-- NOT USED IN THIS DOCUMENT
}
OtherCertID ::= SEQUENCE {
otherCertHash OtherHash,
issuerSerial IssuerSerial OPTIONAL }
OtherHash ::= CHOICE {
sha1Hash OtherHashValue, -- This contains a SHA-1 hash
otherHash OtherHashAlgAndValue}
OtherHashValue ::= OCTET STRING
OtherHashAlgAndValue ::= SEQUENCE {
hashAlgorithm AlgorithmIdentifier,
hashValue OtherHashValue }
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3.9 Additional Mandatory Attributes
3.9.1 Signature policy Identifier
This document mandates that a reference to the signature policy, which
defines the rules for creation and validation of an electronic
signature, is included as a signed attribute with every signature. The
signature policy identifier must be a signed attribute.
The following object identifier identifies the signature policy
identifier attribute:
id-aa-ets-sigPolicyId OBJECT IDENTIFIER ::= { iso(1)
member-body(2) us(840) rsadsi(113549) pkcs(1) pkcs9(9)
smime(16) id-aa(2) 15 }
Signature-policy-identifier attribute values have ASN.1 type
SignaturePolicyIdentifier.
SignaturePolicyIdentifier ::= SEQUENCE {
sigPolicyIdentifier SigPolicyId,
sigPolicyHash SigPolicyHash,
sigPolicyQualifiers SEQUENCE SIZE (1..MAX) OF
SigPolicyQualifierInfo OPTIONAL}
The sigPolicyIdentifier field contains an object-identifier which
uniquely identifies a specific version of the signature policy. The
syntax of this field is as follows:
SigPolicyId ::= OBJECT IDENTIFIER
The sigPolicyHash field contains the identifier of the hash algorithm
and the hash of the value of the signature policy.
If the signature policy is defined using ASN.1 (see 6.1) the hash is
calculated on the value without the outer type and length fields and
the hashing algorithm must be as specified in the field
signPolicyHshAlg.
If the signature policy is defined using another structure, the type of
structure and the hashing algorithm must be either specified as part
of the signature policy, or indicated using a signature policy
qualifier.
SigPolicyHash ::= ETSIHashAlgAndValue
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A signature policy identifier may be qualified with other information
about the qualifier. The semantics and syntax of the qualifier is as
associated with the object-identifier in the sigPolicyQualifierId
field. The general syntax of this qualifier is as follows:
SigPolicyQualifierInfo ::= SEQUENCE {
sigPolicyQualifierId SigPolicyQualifierId,
sigQualifier ANY DEFINED BY sigPolicyQualifierId }
This document specifies the following qualifiers:
* spuri: This contains the web URI or URL reference to the
signature policy
* spUserNotice: This contains a user notice which should be
displayed whenever the signature is validated.
-- sigpolicyQualifierIds defined in this document
SigPolicyQualifierId ::=
OBJECT IDENTIFIER
id-spq-ets-uri OBJECT IDENTIFIER ::= { iso(1)
member-body(2) us(840) rsadsi(113549) pkcs(1) pkcs9(9)
smime(16) id-spq(5) 1 }
SPuri ::= IA5String
id-spq-ets-unotice OBJECT IDENTIFIER ::= { iso(1)
member-body(2) us(840) rsadsi(113549) pkcs(1) pkcs9(9)
smime(16) id-spq(5) 2 }
SPUserNotice ::= SEQUENCE {
noticeRef NoticeReference OPTIONAL,
explicitText DisplayText OPTIONAL}
NoticeReference ::= SEQUENCE {
organization DisplayText,
noticeNumbers SEQUENCE OF INTEGER }
DisplayText ::= CHOICE {
visibleString VisibleString (SIZE (1..200)),
bmpString BMPString (SIZE (1..200)),
utf8String UTF8String (SIZE (1..200)) }
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3.10 CMS Imported Optional Attributes
The following attributes MAY be present with the signed-data defined by
this document. The attributes are defined in ref [CMS] and are imported
into this specification and were appropriate qualified and profiling by
this document.
3.10.1 Countersignature
The syntax of the countersignature attribute type of the ES is as
defined in [CMS].
The countersignature attribute must be an unsigned attribute
3.11 ESS Imported Optional Attributes
The following attributes MAY be present with the signed-data defined by
this document. The attributes are defined in ref [ESS] and are imported
into this specification and were appropriate qualified and profiling by
this document.
3.11.1 Signed Content Reference Attribute
The content reference attribute is a link from one SignedData to
another. It may be used to link a reply to the original message to
which it refers, or to incorporate by reference one SignedData into
another.
The content reference attribute MUST be used as defined in [ESS].
The content reference MUST be a signed attribute.
The syntax of the content reference attribute type of the ES is as
defined in [ESS].
3.11.2 Content Identifier Attribute
The content identifier attribute provides an identifier for the signed
content for use when reference may be later required to that content,
for example in the content reference attribute in other signed data sent
later.
The content identifier must be a signed attribute.
The syntax of the content identifier attribute type of the ES is as
defined in [ESS].
The minimal signedContentIdentifier should contain a concatenation of
user-specific identification information (such as a user name or public
keying material identification information), a GeneralizedTime string,
and a random number.
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3.12 Additional Optional Attributes
3.12.1 Commitment Type Indication Attribute
There may be situation were a signer wants to explicitly indicate to a
verifier that by signing the data, it illustrates a type of commitment
on behalf of the signer. The commitmentTypeIndication attribute conveys
such information.
The commitmentTypeIndication attribute must be a signed attribute
The commitment type may be:
* defined as part of the signature policy, in which case the
commitment type has precise semantics that is defined as part of
the signature policy.
* be a registered type, in which case the commitment type has
precise semantics defined by registration, under the rules of the
registration authority. Such a registration authority may be a
trading association or a legislative authority.
The signature policy specifies a set of attributes that it
"recognizes". This "recognized" set includes all those commitment types
defined as part of the signature policy as well as any externally
defined commitment types that the policy may choose to recognize. Only
recognized commitment types are allowed in this field.
The following object identifier identifies the commitment type
indication attribute:
id-aa-ets-commitmentType OBJECT IDENTIFIER ::= { iso(1) member-body(2)
us(840) rsadsi(113549) pkcs(1) pkcs-9(9) smime(16) id-aa(2) 16}
Commitment-Type-Indication attribute values have ASN.1 type
CommitmentTypeIndication.
CommitmentTypeIndication ::= SEQUENCE {
commitmentTypeId CommitmentTypeIdentifier,
commitmentTypeQualifier SEQUENCE SIZE (1..MAX) OF
CommitmentTypeQualifier
OPTIONAL}
CommitmentTypeIdentifier ::= OBJECT IDENTIFIER
CommitmentTypeQualifier ::= SEQUENCE {
commitmentTypeIdentifier CommitmentTypeIdentifier,
qualifier ANY DEFINED BY commitmentTypeIdentifier }
The use of any qualifiers to the commitment type is outside the scope
of this document.
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The following generic commitment types are defined in this document:
id-cti-ets-proofOfOrigin OBJECT IDENTIFIER ::= { iso(1) member-
body(2) us(840) rsadsi(113549) pkcs(1) pkcs-9(9) smime(16)
cti(6) 1}
id-cti-ets-proofOfReceipt OBJECT IDENTIFIER ::= { iso(1) member-
body(2) us(840) rsadsi(113549) pkcs(1) pkcs-9(9) smime(16)
cti(6) 2}
id-cti-ets-proofOfDelivery OBJECT IDENTIFIER ::= { iso(1)
member-body(2) us(840) rsadsi(113549) pkcs(1) pkcs-9(9)
smime(16) cti(6) 3}
id-cti-ets-proofOfSender OBJECT IDENTIFIER ::= { iso(1) member-
body(2) us(840) rsadsi(113549) pkcs(1) pkcs-9(9) smime(16)
cti(6) 4}
id-cti-ets-proofOfApproval OBJECT IDENTIFIER ::= { iso(1)
member-body(2) us(840) rsadsi(113549) pkcs(1) pkcs-9(9)
smime(16) cti(6) 5}
id-cti-ets-proofOfCreation OBJECT IDENTIFIER ::= { iso(1)
member-body(2) us(840) rsadsi(113549) pkcs(1) pkcs-9(9)
smime(16) cti(6) 6}
These generic commitment types have the following meaning:
Proof of origin indicates that the signer recognizes to have created,
approved and sent the message.
Proof of receipt indicates that signer recognizes to have received the
content of the message.
Proof of delivery indicates that the TSP providing that indication has
delivered a message in a local store accessible to the recipient of the
message.
Proof of sender indicates that the entity providing that indication has
sent the message (but not necessarily created it).
Proof of approval indicates that the signer has approved the content of
the message.
Proof of creation indicates that the signer has created the message
(but not necessarily approved, nor sent it).
NOTE: See clause A.3 for a full description of the commitment types
defined above.
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3.12.2 Signer Location
The signer-location attribute is an attribute which specifies a
mnemonic for an address associated with the signer at a particular
geographical (e.g. city) location. The mnemonic is registered in the
country in which the signer is located and is used in the provision of
the Public Telegram Service (according to ITU-T Recommendation F.1
[5?????]).
The signer-location attribute must be a signed attribute.
The following object identifier identifies the signer-location
attribute:
id-aa-ets-signerLocation OBJECT IDENTIFIER ::= { iso(1) member-body(2)
us(840) rsadsi(113549) pkcs(1) pkcs-9(9) smime(16) id-aa(2) 17}
Signer-location attribute values have ASN.1 type SignerLocation:
SignerLocation ::= SEQUENCE {
-- at least one of the following must be present
countryName [0] DirectoryString OPTIONAL,
-- As used to name a Country in X.500
localityName [1] DirectoryString OPTIONAL,
-- As used to name a locality in X.500
postalAdddress [2] PostalAddress OPTIONAL }
PostalAddress ::= SEQUENCE SIZE(1..6) OF DirectoryString
3.12.3 Signer Attributes
The signer-attributes attribute is an attribute which specifies
additional attributes of the signer (e.g. role).
It may be either:
* claimed attributes of the signer;
* certified attributes of the signer;
* the signer-attribute attribute must be a signed attribute
attributes.
The signer-attributes attribute must be a signed attribute.
The following object identifier identifies the signer-attribute
attribute:
id-aa-ets-signerAttr OBJECT IDENTIFIER ::= { iso(1) member-body(2)
us(840) rsadsi(113549) pkcs(1) pkcs-9(9) smime(16) id-aa(2) 18}
signer-attribute attribute values have ASN.1 type SignerAttribute.
SignerAttribute ::= SEQUENCE OF CHOICE {
claimedAttributes [0] ClaimedAttributes,
certifiedAttributes [1] CertifiedAttributes }
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ClaimedAttributes ::= SEQUENCE OF Attribute
CertifiedAttributes ::= AttributeCertificate
-- As defined in X.509 : see section 10.3
NOTE: The claimed and certified attribute are imported from ITU-T
Recommendations X.501 [16] and ITU-T Recommendation X.509 : Draft
Amendment on Certificate Extensions, October 1999.
3.12.3 Content Timestamp
The content timestamp attribute is an attribute which is the timestamp
of the signed data content before it is signed.
The content timestamp attribute must be a signed attribute.
The following object identifier identifies the signer-attribute
attribute:
id-aa-ets-contentTimestamp OBJECT IDENTIFIER ::= { iso(1)
member-body(2) us(840) rsadsi(113549) pkcs(1) pkcs-9(9)
smime(16) id-aa(2) 20}
Content timestamp attribute values have ASN.1 type ContentTimestamp:
ContentTimestamp::= TimeStampToken
The value of messageImprint field within TimeStampToken must be a hash
of the value of eContent field within encapContentInfo within the
signedData.
For further information and definition of TimeStampToken see ref .. temp
note; need to add the reference to the timestamping RFC.
3.13 Support for Multiple Signatures
3.13.1 Independent Signatures
Multiple independent signatures (see clause 55) are supported by
independent SignerInfo from each signer.
Each SignerInfo must include all the attributes required under this
document and must be processed independently by the verifier.
3.13.2 Embedded Signatures
Multiple embedded signatures (see clause B.6) are supported using the
counter-signature unsigned attribute (see clause 10.1). Each counter
signature is carried in Countersignature held as an unsigned attribute
to the SignerInfo to which the counter-signature is applied.
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4. Validation Data
This clause specifies the validation data structures which builds on
the electronic signature specified in clause 3. This includes:
* Timestamp applied to the electronic signature value.
* Complete validation data which comprises the timestamp of the
signature value, plus references to all the certificates and
revocation information used for full validation of the electronic
signature.
The following optional eXtended forms of validation data are also
defined:
* X-timestamp: There are two types of timestamp used in extended
validation data defined by this document.
- Type 1 -Timestamp which comprises a timestamp over the ES
with Complete validation data (ES-C).
- Type 2 X-Timestamp which comprises of a timestamp over the
certification path references and the revocation information
references used to support the ES-C.
* X-Long : This comprises a Complete validation data
plus the actual values of all the certificates and
revocation information used in the ES-C.
* X-Long-Timestamp: This comprises a Type 1 or Type 2
X-Timestamp plus the actual values of all the
certificates and revocation information used in the
ES-C.
This clause also specifies the data structures used in Archive
validation data:
* Archive validation data comprises a Complete validation data,
the certificate and revocation values (as in a X-Long
validation data), any other existing X-timestamps, plus the
Signed User data and an additional archive timestamp over all
that data. An archive timestamp may be repeatedly applied
after long periods to maintain validity when electronic
signature and timestamping algorithms weaken.
The additional data required to create the forms of electronic
signature identified above is carried as unsigned attributes associated
with an individual signature by being placed in the unsignedAttrs field
of SignerInfo (see clause 6????). Thus all the attributes defined in
clause 9?? are unsigned attributes.
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NOTE: Where multiple signatures are to be supported, as described in
clause 3.13, each signature has a separate SignerInfo. Thus, each
signature requires its own unsigned attribute values to create ES-T,
ES-C etc.
4.1 Electronic Signature Timestamp
An Electronic Signature with Timestamp is an Electronic Signature for
which part, but not all, of the additional data required for validation
is available (i.e. some certificates and revocation information is
available but not all). The minimum structure Timestamp validation data
is:
* The Signature Timestamp Attribute as defined in clause 4.1.1
over the ES signature value.
4.1.1 Signature Timestamp Attribute Definition
The Signature Timestamp attribute is timestamp of the signature value.
It is an unsigned attribute. Several instances of this attribute may
occur with an electronic signature, from different TSAs.
The Signature Validation Policy specifies, in the
signatureTimestampDelay field of TimestampTrustConditions, an maximum
acceptable time difference which is allowed between the time indicated
in the signing time attribute and the time indicated by the Signature
Timestamp attribute. If this delay is exceeded then the electronic
signature must be considered as invalid.
The following object identifier identifies the Signature Timestamp
attribute:
id-aa-signatureTimeStampToken OBJECT IDENTIFIER ::= { iso(1)
member-body(2) us(840) rsadsi(113549) pkcs(1) pkcs-9(9) smime(16)
id-aa(2) 14}
The Signature timestamp attribute value has ASN.1 type
SignatureTimeStampToken:
SignatureTimeStampToken ::= TimeStampToken
The value of messageImprint field within TimeStampToken must be a hash
of the value of signature field within SignerInfo for the signedData
being timestamped.
For further information and definition of TimeStampToken see [TSP]
Temp note ;ref to timestamping doc required
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4.2 Complete Validation Data
An electronic signature with complete validation data is an Electronic
Signature for which all the additional data required for validation
(i.e. all certificates and revocation information) is available.
Complete validation data (ES-C) build on the electronic signature
Timestamp as defined above.
The minimum structure of a Complete validation data is:
* the Signature Timestamp Attribute, as defined in clause 4.1.1;
* Complete Certificate Refs, as defined in clause 4.2.1;
* Complete Revocation Refs, as defined in clause 4.2.2.
The Complete validation data MAY also include the following additional
information, forming a X-Long validation data, for use if later
validation processes may not have access to this information:
* Complete Certificate Values, as defined in clause 4.2.3;
* Complete Revocation Values, as defined in clause 4.2.4.
The Complete validation data MAY also include one of the following
additional attributes, forming a X-Timestamp validation data, to
provide additional protection against later CA compromise and provide
integrity of the validation data used:
* ES-C Timestamp, as defined in clause 4.2.5; or
* Time-Stamped Certificates and CRLs references, as defined in
clause 4.2.6.
NOTE 1: As long as the CA's are trusted such that these keys cannot
be compromised or the cryptography used broken, the ES-C provides long
term proof of a valid electronic signature.
A valid electronic signature is an electronic signature which passes
validation according to a signature validation policy.
NOTE 2: The ES-C provides the following important property for long
standing signatures; that is having been found once to be valid, must
continue to be so months or years later. Long after the validity period
of the certificates have expired, or after the user key has been
compromised.
4.2.1 Complete Certificate Refs Attribute Definition
The Complete Certificate Refs attribute is an unsigned attribute. It
references the full set of CA certificates that have been used to
validate a ES with Complete validation data (ES-C) up to (but not
including) the signer's certificate. Only a single instance of this
attribute must occur with an electronic signature.
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Note: The signer's certified is referenced in the signing certificate
attribute (see clause 3.1).
id-aa-ets-certificateRefs OBJECT IDENTIFIER ::= { iso(1) member-body(2)
us(840) rsadsi(113549) pkcs(1) pkcs-9(9) smime(16) id-aa(2) 21}
The complete certificate refs attribute value has the ASN.1 syntax
CompleteCertificateRefs.
CompleteCertificateRefs ::= SEQUENCE OF ETSICertID
ETSICertID is defined in clause 3.8.2.
The IssuerSerial that must be present in ETSICertID. The certHash
must match the hash of the certificate referenced.
NOTE: Copies of the certificate values may be held using the
Certificate Values attribute defined in clause 4.3.1.
4.2.2 Complete Revocation Refs Attribute Definition
The Complete Revocation Refs attribute is an unsigned attribute. Only a
single instance of this attribute must occur with an electronic
signature. It references the full set of the CRL or OCSP responses that
have been used in the validation of the signer and CA certificates
used in ES with Complete validation data.
The following object identifier identifies the CompleteRevocationRefs
attribute:
id-aa-ets-revocationRefs OBJECT IDENTIFIER ::= { iso(1) member-body(2)
us(840) rsadsi(113549) pkcs(1) pkcs-9(9) smime(16) id-aa(2) 22}
The complete revocation refs attribute value has the ASN.1 syntax
CompleteRevocationRefs
CompleteRevocationRefs ::= SEQUENCE OF CrlOcspRef
CrlOcspRef ::= SEQUENCE {
crlids [0] CRLListID OPTIONAL,
ocspids [1] OcspListID OPTIONAL,
otherRev [2] OtherRevRefs OPTIONAL
}
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CompleteRevocationRefs must contain one CrlOcspRef for the signing
certificate, followed by one for each ETSICertID in the
CompleteCertificateRefs attribute. the second and subsequent CrlOcspRef
fields must be in the same order as the ETSICertID to which they
relate. At least one of CRLListID or OcspListID or OtherRevRefs should
be present for all but the "trusted" CA of the certificate path.
CRLListID ::= SEQUENCE {
crls SEQUENCE OF CrlValidatedID}
CrlValidatedID ::= SEQUENCE {
crlHash ETSIHash,
crlIdentifier CrlIdentifier OPTIONAL}
CrlIdentifier ::= SEQUENCE {
crlissuer Name,
crlIssuedTime UTCTime,
crlNumber INTEGER OPTIONAL
}
OcspListID ::= SEQUENCE {
ocspResponses SEQUENCE OF OcspResponsesID}
OcspResponsesID ::= SEQUENCE {
ocspIdentifier OcspIdentifier,
ocspRepHash ETSIHash OPTIONAL
}
OcspIdentifier ::= SEQUENCE {
ocspResponderID ResponderID,
-- As in OCSP response data
producedAt GeneralizedTime
-- As in OCSP response data
}
When creating an crlValidatedID, the crlHash is computed over the
entire DER encoded CRL including the signature. The crlIdentifier would
normally be present unless the CRL can be inferred from other
information.
The crlIdentifier is to identify the CRL using the issuer name and the
CRL issued time which must correspond to the time "thisUpdate"
contained in the issued CRL. The crlListID attribute is an unsigned
attribute. In the case that the identified CRL is a Delta CRL then
references to the set of CRLs to provide a complete revocation list
must be included.
The OcspIdentifier is to identify the OSCP response using the issuer
name and the time of issue of the OCSP response which must correspond
to the time "producedAt" contained in the issued OCSP response. Since
it may be needed to make the difference between two OCSP responses
received within the same second, then the hash of the response contained
in the OcspResponsesID may be needed to solve the ambiguity.
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NOTE: Copies of the CRL and OCSP responses values may be held using the
Revocation Values attribute defined in clause 4.3.2.
OtherRevRefs ::= SEQUENCE {
otherRevRefType OtherRevRefType,
otherRevRefs ANY DEFINED BY otherRevRefType
}
OtherRevRefType ::= OBJECT IDENTIFIER
The syntax and semantics of other revocation references is outside the
scope of this document. The definition of the syntax of the other form
of revocation information is as identified by OtherRevRefType.
4.3 Extended Validation Data
4.3.1 Certificate Values Attribute Definition
The Certificate Values attribute is an unsigned attribute. Only a
single instance of this attribute must occur with an electronic
signature. It holds the values of certificates referenced in the
CompleteCertificateRefs attribute.
Note: If an Attribute Certificate is used, it is not provided in this
structure but must be provided by the signer as a signer-attributes
attribute (see clause 12.3).
The following object identifier identifies the CertificateValues
attribute:
id-aa-ets-certValues OBJECT IDENTIFIER ::= { iso(1) member-body(2)
us(840) rsadsi(113549) pkcs(1) pkcs-9(9) smime(16) id-aa(2) 23}
The certificate values attribute value has the ASN.1 syntax
CertificateValues
CertificateValues ::= SEQUENCE OF Certificate
Certificate is defined in clause 10.1 (which is as defined in ITU-T
Recommendation X.509 [1])
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4.3.2 Revocation Values Attribute Definition
The Revocation Values attribute is an unsigned attribute. Only a single
instance of this attribute must occur with an electronic signature.
It holds the values of CRLs and OCSP referenced in the
CompleteRevocationRefs attribute.
The following object identifier identifies the CertificateValues
attribute:
id-aa-ets-revocationValues OBJECT IDENTIFIER ::= { iso(1) member-
body(2)
us(840) rsadsi(113549) pkcs(1) pkcs-9(9) smime(16) id-aa(2) 24}
The revocation values attribute value has the ASN.1 syntax
RevocationValues
RevocationValues ::= SEQUENCE {
crlVals [0] SEQUENCE OF CertificateList OPTIONAL,
ocspVals [1] SEQUENCE OF BasicOCSPResponse OPTIONAL,
otherRevVals [2] OtherRevVals }
OtherRevVals ::= SEQUENCE {
otherRevValType OtherRevValType,
otherRevVals ANY DEFINED BY otherRevValType
}
OtherRevValType ::= OBJECT IDENTIFIER
The syntax and semantics of the other revocation values is outside the
scope of this document. The definition of the syntax of the other form
of revocation information is as identified by OtherRevRefType.
CertificateList is defined in clause 10.2 (which as defined in ITU-T
Recommendation X.509 [1]).
BasicOCSPResponse is defined in clause 10.3 (which as defined in ??? RFC
2560 [8] ???).
4.3.3 ES-C Timestamp Attribute Definition
This attribute is used for the Type 1 X-Timestamped validation data.
The ES-C Timestamp attribute is an unsigned attribute. It is timestamp
of a hash of the electronic signature and the complete validation data
(ES-C). It is a special purpose TimeStampToken Attribute which
timestamps the ES-C. Several instances instance of this attribute may
occur with an electronic signature from different TSAs.
The following object identifier identifies the ES-C Timestamp
attribute:
id-aa-ets-escTimeStamp OBJECT IDENTIFIER ::= { iso(1) member-body(2)
us(840) rsadsi(113549) pkcs(1) pkcs-9(9) smime(16) id-aa(2) 25}
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The ES-C timestamp attribute value has the ASN.1 syntax
ESCTimeStampToken.
ESCTimeStampToken ::= TimeStampToken
The value of messageImprint field within TimeStampToken must be a hash
of the concatenated values (without the type or length encoding for
that value) of the following data objects as present in the ES with
Complete validation data (ES-C):
* signature field within SignerInfo;
* SignatureTimeStampToken attribute;
* CompleteCertificateRefs attribute;
* CompleteRevocationRefs attribute.
For further information and definition of the Time Stamp Token see
clause [TSP].
Temp note ;ref to timestamping doc required.
4.3.4 Time-Stamped Certificates and CRLs Attribute Definition
This attribute is used for the Type 2 X-Timestamp validation data. A
TimestampedCertsCRLsRef attribute is an unsigned attribute. It is a
list of referenced certificates and OCSP responses/CRLs which are been
timestamped to protect against certain CA compromises. Its syntax is as
follows:
The following object identifier identifies the TimestampedCertsCRLsRef
attribute:
id-aa-ets-certCRLTimestamp OBJECT IDENTIFIER ::= { iso(1) member-
body(2)
us(840) rsadsi(113549) pkcs(1) pkcs-9(9) smime(16) id-aa(2) 26}
The attribute value has the ASN.1 syntax TimestampedCertsCRLs.
TimestampedCertsCRLs ::= TimeStampToken
The value of messageImprint field within TimeStampToken must be a hash
of the concatenated values (without the type or length encoding for
that value) of the following data objects as present in the ES with
Complete validation data (ES-C):
* CompleteCertificateRefs attribute;
* CompleteRevocationRefs attribute.
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4.4 Archive Validation Data
Where an electronic signature is required to last for a very long time,
and a the timestamp on an electronic signature is in danger of being
invalidated due to algorithm weakness or limits in the validity period
of the TSA certificate, then it may be required to timestamp the
electronic signature several times. When this is required an archive
timestamp attribute may be required. This timestamp may be repeatedly
applied over a period of time.
4.4.1 Archive Timestamp Attribute Definition
The Archive Timestamp attribute is timestamp of the user data and the
entire electronic signature. If the Certificate values and Revocation
Values attributes are not present these attributes must be added to
the electronic signature prior to the timestamp. The Archive Timestamp
attribute is an unsigned attribute. Several instances of this attribute
may occur with on electronic signature both over time and from
different TSAs.
The following object identifier identifies the Nested Archive Timestamp
attribute:
id-aa-ets-archiveTimestamp OBJECT IDENTIFIER ::= { iso(1) member-
body(2)
us(840) rsadsi(113549) pkcs(1) pkcs-9(9) smime(16) id-aa(2) 27}
Archive timestamp attribute values have the ASN.1 syntax
ArchiveTimeStampToken
ArchiveTimeStampToken ::= TimeStampToken
The value of messageImprint field within TimeStampToken must be a hash
of the concatenated values (without the type or length encoding for
that value) of the following data objects as present in the electronic
signature:
* encapContentInfo eContent OCTET STRING;
* signedAttributes;
* signature field within SignerInfo;
* SignatureTimeStampToken attribute;
* CompleteCertificateRefs attribute;
* CompleteRevocationData attribute;
* CertificateValues attribute
(If not already present this information must be included in the
ES-A);
* RevocationValues attribute
(If not already present this information must be included in the
ES-A);
* ESCTimeStampToken attribute if present;
* TimestampedCertsCRLs attribute if present;
* any previous ArchiveTimeStampToken attributes.
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For further information and definition of TimeStampToken see see [TSP]
Temp note ;ref to timestamping doc required
The timestamp should be created using stronger algorithms (or longer
key lengths) than in the original electronic signatures and weak
algorithm (key length) timestamps .
5. Signature Policy Specification
This document mandates that:
* an electronic signature must be processed by the signer and
verifier in accordance with the signature policy as identified
by the signature policy attribute (see clause 4.1);
* the signature policy must be identifiable by an Object
Identifier;
* there must exist a specification of the signature policy;
* for a given signature policy there must be one definitive form
of the specification which has a unique binary encoding;
* a hash of the definitive specification, using an agreed
algorithm, must be provided by the signer and checked by the
verifier (see clause 4.1).
A signature policy specification includes general information about the
policy, the validation policy rules and other signature policy
information.
Clause 6 describes the kind of information to be included in a
signature policy.
The current document does not mandate the form of the signature policy
specification. The signature policy may be specified either:
* in a free form document for human interpretation; or
* in a structured form using an agreed syntax and encoding.
This document defines an ASN.1 based syntax that may be used to define
a structured signature policy.
5.1 Overall ASN.1 Structure
The overall structure of a signature policy defined using ASN.1 is
given in this clause. Use of this ASN.1 structure is optional.
This ASN.1 syntax is encoded using the Distinguished Encoding Rules
(DER).
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In this structure the policy information is preceded by an identifier
for the hashing algorithm used to protect the signature policy and
followed by the hash value which must be re-calculated and checked
whenever the policy is passed between the issuer and signer/verifier.
The hash is calculated without the outer type and length fields.
SignaturePolicy ::= SEQUENCE {
signPolicyHashAlg AlgorithmIdentifier,
signPolicyInfo SignPolicyInfo,
signPolicyHash SignPolicyHash OPTIONAL }
SignPolicyHash ::= OCTET STRING
SignPolicyInfo ::= SEQUENCE {
signPolicyIdentifier SignPolicyId,
dateOfIssue GeneralizedTime,
policyIssuerName PolicyIssuerName,
fieldOfApplication FieldOfApplication,
signatureValidationPolicy SignatureValidationPolicy,
signPolExtensions SignPolExtensions
OPTIONAL
}
SignPolicyId ::= OBJECT IDENTIFIER
The policyIssuerName field identifies the policy issuer in one or more
of the general name forms.
PolicyIssuerName ::= GeneralNames
The fieldofApplication is a description of the expected application of
this policy.
FieldOfApplication ::= DirectoryString
The signature validation policy rules are fully processable to allow
the validation of electronic signatures issued under that signature
policy. They are described in the rest of this clause.
5.2 Signature Validation Policy
The signature validation policy defines for the signer which data
elements must be present in the electronic signature he provides and
for the verifier which data elements must be present under that
signature policy for an electronic signature to be potentially valid.
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The signature validation policy is described as follows:
SignatureValidationPolicy ::= SEQUENCE {
signingPeriod SigningPeriod,
commonRules CommonRules,
commitmentRules CommitmentRules,
signPolExtensions SignPolExtensions OPTIONAL
}
The signingPeriod identifies the date and time before which the
signature policy should not be used for creating signatures, and an
optional date after which it should not be used for creating
signatures.
SigningPeriod ::= SEQUENCE {
notBefore GeneralizedTime,
notAfter GeneralizedTime OPTIONAL }
5.3 Common Rules
The CommonRules define rules that are common to all commitment types.
These rules are defined in terms of trust conditions for certificates,
timestamps and attributes, along with any constraints on attributes
that may be included in the electronic signature.
CommonRules ::= SEQUENCE {
signerAndVeriferRules [0] SignerAndVerifierRules
OPTIONAL,
signingCertTrustCondition [1] SigningCertTrustCondition
OPTIONAL,
timeStampTrustCondition [2] TimestampTrustCondition
OPTIONAL,
attributeTrustCondition [3] AttributeTrustCondition
OPTIONAL,
algorithmConstraintSet [4] AlgorithmConstraintSet
OPTIONAL,
signPolExtensions [5] SignPolExtensions
OPTIONAL
}
If a field is present in CommonRules then the equivalent field must
not be present in any of the CommitmentRules (see below). If any of the
following fields are not present in CommonRules then it must be
present in each CommitmentRule:
* signerAndVeriferRules;
* signingCertTrustCondition;
* timeStampTrustCondition.
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5.4 Commitment Rules
The CommitmentRules consists of the validation rules which apply to
given commitment types:
CommitmentRules ::= SEQUENCE OF CommitmentRule
The CommitmentRule for given commitment types are defined in terms of
trust conditions for certificates, timestamps and attributes, along
with any constraints on attributes that may be included in the
electronic signature.
CommitmentRule ::= SEQUENCE {
selCommitmentTypes SelectedCommitmentTypes,
signerAndVeriferRules [0] SignerAndVerifierRules
OPTIONAL,
signingCertTrustCondition [1] SigningCertTrustCondition
OPTIONAL,
timeStampTrustCondition [2] TimestampTrustCondition
OPTIONAL,
attributeTrustCondition [3] AttributeTrustCondition
OPTIONAL,
algorithmConstraintSet [4] AlgorithmConstraintSet
OPTIONAL,
signPolExtensions [5] SignPolExtensions
OPTIONAL
}
SelectedCommitmentTypes ::= SEQUENCE OF CHOICE {
empty NULL,
recognizedCommitmentType CommitmentType }
If the SelectedCommitmentTypes indicates "empty" then this rule applied
when a commitment type is not present (i.e.the type of commitment is
indicated in the semantics of the message). Otherwise, the electronic
signature must contain a commitment type indication that must fit one
of the commitments types that are mentioned in CommitmentType.
A specific commitment type identifier must not appear in more than one
commitment rule.
CommitmentType ::= SEQUENCE {
identifier CommitmentTypeIdentifier,
fieldOfApplication [0] FieldOfApplication OPTIONAL,
semantics [1] DirectoryString OPTIONAL }
The fieldOfApplication and semantics fields define the specific use and
meaning of the commitment within the overall field of application
defined for the policy.
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5.5 Signer and Verifier Rules
The SignerAndVerifierRules consists of signer rule and verification
rules as defined below:
SignerAndVerifierRules ::= SEQUENCE {
signerRules SignerRules,
verifierRules VerifierRules }
5.5.1 Signer Rules
The signer rules identify:
* if the eContent is empty and the signature is calculated using
a hash of signed data external to CMS structure.
* the CMS signed attributes that must be provided by the signer
under this policy;
* the CMS unsigned attribute that must be provided by the signer
under this policy;
* whether the certificate identifiers from the full certification
path up to the trust point must be provided by the signer in
the SigningCertificate attribute;
* whether a signer's certificate, or all certificates in the
certification path to the trust point must be provided by the
signer in the certificates field of SignedData.
SignerRules ::= SEQUENCE {
externalSignedData BOOLEAN OPTIONAL,
-- True if signed data is external to CMS structure
-- False if signed data part of CMS structure
-- not present if either allowed
mandatedSignedAttr CMSAttrs,
-- Mandated CMS signed attributes
mandatedUnsignedAttr CMSAttrs,
-- Mandated CMS unsigned attributed
mandatedCertificateRef [0] CertRefReq DEFAULT signerOnly,
-- Mandated Certificate Reference
mandatedCertificateInfo [1] CertInfoReq DEFAULT none,
-- Mandated Certificate Info
signPolExtensions [2] SignPolExtensions OPTIONAL
}
CMSAttrs ::= SEQUENCE OF OBJECT IDENTIFIER
The mandatedSignedAttr field must include the object identifier for
all those signed attributes required by this document as well as
additional attributes required by this policy.
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The mandatedUnsignedAttr field must include the object identifier for
all those unsigned attributes required by this document as well as
additional attributes required this policy. For example, if a signature
timestamp (see clause 1.1) is required by the signer the object
identifier for this attribute must be included.
The mandatedCertificateRef identifies whether just the signer's
certificate, or all the full certificate path must be provided by the
signer.
CertRefReq ::= ENUMERATED {
signerOnly (1),
-- Only reference to signer cert mandated
fullPath (2)
-- References for full cert path up to a trust point required
}
The mandatedCertificateInfo field identifies whether a signer's
certificate, or all certificates in the certification path to the trust
point must be provided by the signer in the certificates field of
SignedData.
CertInfoReq ::= ENUMERATED {
none (0) ,
-- No mandatory requirements
signerOnly (1) ,
-- Only reference to signer cert mandated
fullPath (2)
-- References for full cert path up to a
-- trust point mandated
}
5.5.2 Verifier Rules
The verifier rules identify:
* The CMS unsigned attributes that must be present under this policy
and must be added by the verifier if not added by the signer.
VerifierRules ::= SEQUENCE {
mandatedUnsignedAttr MandatedUnsignedAttr,
signPolExtensions SignPolExtensions OPTIONAL
}
MandatedUnsignedAttr ::= CMSAttrs
-- Mandated CMS unsigned attributed
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5.6 Certificate and Revocation Requirement
The SigningCertTrustCondition, TimestampTrustCondition and
AttributeTrustCondition (defined in subsequent sub-clauses) make use of
two ASN1 structures which are defined below: CertificateTrustTrees and
CertRevReq.
5.6.1 Certificate Requirements
The certificateTrustTrees identifies a set of self signed certificates
for the trust points used to start (or end) certificate path processing
and the initial conditions for certificate path validation as defined
RFC 2459 [7] section 5. This ASN1 structure is used to define policy
for validating the signing certificate, the TSA's certificate and
attribute certificates.
CertificateTrustTrees ::= SEQUENCE OF CertificateTrustPoint
CertificateTrustPoint ::= SEQUENCE {
trustpoint Certificate,
-- self-signed certificate
pathLenConstraint [0] PathLenConstraint OPTIONAL,
acceptablePolicySet [1] AcceptablePolicySet OPTIONAL,
-- If not present "any policy"
nameConstraints [2] NameConstraints OPTIONAL,
policyConstraints [3] PolicyConstraints OPTIONAL }
The trustPoint field gives the self signed certificate for the CA that
is used as the trust point for the start of certificate path
processing.
The pathLenConstraint field gives the maximum number of CA certificates
that may be in a certification path following the trustpoint. A value
of zero indicates that only the given trustpoint certificate and an
end-entity certificate may be used. If present, the pathLenConstraint
field must be greater than or equal to zero. Where pathLenConstraint
is not present, there is no limit to the allowed length of the
certification path.
PathLenConstraint ::= INTEGER (0..MAX)
The acceptablePolicySet field identifies the initial set of certificate
policies, any of which are acceptable under the signature policy.
AcceptablePolicySet ::= SEQUENCE OF CertPolicyId
CertPolicyId ::= OBJECT IDENTIFIER
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The nameConstraints field indicates a name space within which all
subject names in subsequent certificates in a certification path must
be located. Restrictions may apply to the subject distinguished name or
subject alternative names. Restrictions apply only when the specified
name form is present. If no name of the type is in the certificate, the
certificate is acceptable.
Restrictions are defined in terms of permitted or excluded name
subtrees. Any name matching a restriction in the excludedSubtrees field
is invalid regardless of information appearing in the ermittedSubtrees.
NameConstraints ::= SEQUENCE {
permittedSubtrees [0] GeneralSubtrees OPTIONAL,
excludedSubtrees [1] GeneralSubtrees OPTIONAL }
GeneralSubtrees ::= SEQUENCE SIZE (1..MAX) OF GeneralSubtree
GeneralSubtree ::= SEQUENCE {
base GeneralName,
minimum [0] BaseDistance DEFAULT 0,
maximum [1] BaseDistance OPTIONAL }
BaseDistance ::= INTEGER (0..MAX)
The policyConstraints extension constrains path processing in two ways.
It can be used to prohibit policy mapping or require that each
certificate in a path contain an acceptable policy identifier.
The policyConstraints field, if present specifies requirement for
explicit indication of the certificate policy and/or the constraints on
policy mapping.
PolicyConstraints ::= SEQUENCE {
requireExplicitPolicy [0] SkipCerts OPTIONAL,
inhibitPolicyMapping [1] SkipCerts OPTIONAL }
SkipCerts ::= INTEGER (0..MAX)
If the inhibitPolicyMapping field is present, the value indicates the
number of additional certificates that may appear in the path
(including the trustpoint's self certificate) before policy mapping is
no longer permitted. For example, a value of one indicates that policy
mapping may be processed in certificates issued by the subject of this
certificate, but not in additional certificates in the path.
If the requireExplicitPolicy field is present, subsequent certificates
must include an acceptable policy identifier. The value of
requireExplicitPolicy indicates the number of additional certificates
that may appear in the path (including the trustpoint's self
certificate) before an explicit policy is required. An acceptable
policy identifier is the identifier of a policy required by the user of
the certification path or the identifier of a policy which has been
declared equivalent through policy mapping.
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5.6.2 Revocation Requirements
The RevocRequirements field specifies minimum requirements for
revocation information, obtained through CRLs and/or OCSP responses, to
be used in checking the revocation status of certificates. This ASN1
structure is used to define policy for validating the signing
certificate, the TSA's certificate and attribute certificates.
CertRevReq ::= SEQUENCE {
endCertRevReq RevReq,
caCerts [0] RevReq
}
Certificate revocation requirements are specified in terms of checks
required on:
* endCertRevReq: end certificates (i.e. the signers certificate,
the attribute certificate or the timestamping authority
certificate).
* caCerts: CA certificates.
RevReq ::= SEQUENCE {
enuRevReq EnuRevReq,
exRevReq SignPolExtensions OPTIONAL}
An authority certificate is certificate issued to an authority (e.g.
either to a certification authority or to an attribute authority (AA)).
A TimeStamping Authority (TSA) is a trusted third party that creates
time stamp tokens in order to indicate that a datum existed at a
particular point in time (RFC??: "Internet X.509 Public Key
Infrastructure - Time Stamp Protocol").
EnuRevReq ::= ENUMERATED {
clrCheck (0),
--Checks must be made against current CRLs
-- (or authority revocation lists (ARL))
ocspCheck (1), -- The revocation status must be checked
-- using the Online Certificate Status Protocol
-- (OCSP),RFC 2450.
bothCheck (2),
-- Both CRL and OCSP checks must be carried out
eitherCheck (3),
-- At least one of CRL or OCSP checks must be
-- carried out
noCheck (4),
-- no check is mandated
other (5)
-- Other mechanism as defined by signature poilicy
-- extension
}
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Revocation requirements are specified in terms of:
* clrCheck: Checks must be made against current CRLs (or
authority revocation lists);
* ocspCheck: The revocation status must be checked using the
Online Certificate Status Protocol (RFC 2450);
* bothCheck: Both OCSP and CRL checks must be carried out;
* eitherCheck: Either OCSP or CRL checks must be carried out;
* noCheck: No check is mandated.
5.7 Signing Certificate Trust Conditions
The SigningCertTrustCondition field identifies trust conditions for
certificate path processing used to validate the signing certificate.
SigningCertTrustCondition ::= SEQUENCE {
signerTrustTrees CertificateTrustTrees,
signerRevReq CertRevReq
}
5.8 TimeStamp Trust Conditions
The TimeStampTrustCondition field identifies trust conditions for
certificate path processing used to authenticate the timstamping
authority and constraints on the name of the timestamping authority.
This applies to the timestamp that must be present in every ES-T.
TimestampTrustCondition ::= SEQUENCE {
ttsCertificateTrustTrees [0] CertificateTrustTrees
OPTIONAL,
ttsRevReq [1] CertRevReq
OPTIONAL,
ttsNameConstraints [2] NameConstraints
OPTIONAL,
cautionPeriod [3] DeltaTime
OPTIONAL,
signatureTimestampDelay [4] DeltaTime
OPTIONAL }
DeltaTime ::= SEQUENCE {
deltaSeconds INTEGER,
deltaMinutes INTEGER,
deltaHours INTEGER,
deltaDays INTEGER }
If ttsCertificateTrustTrees is not present then the same rule as
defined in certificateTrustCondition applies to certification of the
timestamping authorities public key.
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The tstrRevReq specifies minimum requirements for revocation
information, obtained through CRLs and/or OCSP responses, to be used in
checking the revocation status of the time stamp that must be present
in the ES-T.
If ttsNameConstraints is not present then there are no additional
naming constraints on the trusted timestamping authority other than
those implied by the ttsCertificateTrustTrees.
The cautionPeriod field specifies a caution period after the signing
time that it is mandated the verifier must wait to get high assurance
of the validity of the signer's key and that any relevant revocation
has been notified. The revocation status information forming the ES
with Complete validation data must not be collected and used to
validate the electronic signature until after this caution period.
The signatureTimestampDelay field specifies a maximum acceptable time
between the signing time and the time at which the signature timestamp,
as used to form the ES Timestamped, is created for the verifier. If the
signature timestamp is later that the time in the signing-time
attribute by more than the value given in signatureTimestampDelay, the
signature must be considered invalid.
5.9 Attribute Trust Conditions
If the attributeTrustCondition field is not present then any certified
attributes may not considered to be valid under this validation policy.
The AttributeTrustCondition field is defined as follows:
AttributeTrustCondition ::= SEQUENCE {
attributeMandated BOOLEAN,
-- Attribute must be present
howCertAttribute HowCertAttribute,
attrCertificateTrustTrees [0] CertificateTrustTrees OPTIONAL,
attrRevReq [1] CertRevReq OPTIONAL,
attributeConstraints [2] AttributeConstraints OPTIONAL }
If attributeMandated is true then an attribute, certified within the
following constraints, must be present. If false, then the signature
is still valid if no attribute is specified.
The howCertAttribute field specifies whether attributes uncertified
attributes "claimed" by the signer, or certified in an attribute
certificate or either using the signer attributes attribute defined
in 4.12.3.
HowCertAttribute ::= ENUMERATED {
claimedAttribute (0),
certifiedAttribtes (1),
either (2) }
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The attrCertificateTrustTrees specifies certificate path conditions for
any attribute certificate. If not present the same rules apply as in
certificateTrustCondition.
The attrRevReq specifies minimum requirements for revocation
information, obtained through CRLs and/or OCSP responses, to be used in
checking the revocation status of Attribute Certificates, if any are
present.
If the attributeConstraints field is not present then there are no
constraints on the attributes that may be validated under this policy.
The attributeConstraints field is defined as follows:
AttributeConstraints ::= SEQUENCE {
attributeTypeConstarints [0] AttributeTypeConstraints
OPTIONAL,
attributeValueConstarints [1] AttributeValueConstraints
OPTIONAL }
If present, the attributeTypeConstarints field specifies the attribute
types which are considered valid under the signature policy. Any value
for that attribute is considered valid.
AttributeTypeConstraints ::= SEQUENCE OF AttributeType
If present, the attributeTypeConstraints field specifies the specific
attribute values which are considered valid under the signature policy.
AttributeValueConstraints ::= SEQUENCE OF AttributeTypeAndValue
5.10 Algorithm Constraints
The algorithmConstrains fields, if present, identifies the signing
algorithms (hash, public key cryptography, combined hash and public key
cryptography) that may be used for specific purposes and any minimum
length. If this field is not present then the policy applies no
constraints.
AlgorithmConstraintSet ::= SEQUENCE { -- Algorithm constrains on:
signerAlgorithmConstraints [0] AlgorithmConstraints OPTIONAL,
-- signer
eeCertAlgorithmConstraints [1] AlgorithmConstraints OPTIONAL,
-- issuer of end entity certs.
caCertAlgorithmConstraints [2] AlgorithmConstraints OPTIONAL,
-- issuer of CA certificates
aaCertAlgorithmConstraints [3] AlgorithmConstraints OPTIONAL,
-- Attribute Authority
tsaCertAlgorithmConstraints [4] AlgorithmConstraints OPTIONAL
-- TimeStamping Authority
}
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AlgorithmConstraints ::= SEQUENCE OF AlgAndLength
AlgAndLength ::= SEQUENCE {
algID OBJECT IDENTIFIER,
minKeyLength INTEGER OPTIONAL,
-- Minimum key length in bits
other SignPolExtensions OPTIONAL
}
An Attribute Authority (AA)is authority which assigns privileges by
issuing attribute certificates
5.11 Signature Policy Extensions
Additional signature policy rules may be added to:
* the overall signature policy structure, as defined in
clause 5.1;
* the signature validation policy structure, as defined in
clause 5.2;
* the common rules, as defined in clause 5.3;
* the commitment rules, as defined in clause 5.4;
* the signer rules, as defined in clause 5.5.1;
* the verifier rules, as defined in clause 5.5.2;
* the revocation requirements in clause 5.6.2;
* the algorithm constraints in clause 5.10.
These extensions to the signature policy rules must be defined using
an ASN.1 syntax with an associated object identifier carried in the
SignPolExtn as defined below:
SignPolExtensions ::= SEQUENCE OF SignPolExtn
SignPolExtn ::= SEQUENCE {
extnID OBJECT IDENTIFIER,
extnValue OCTET STRING }
The extnID field must contain the object identifier for the extension.
The extnValue field must contain the DER (see ITU-T Recommendation
X.690 [4]) encoded value of the extension. The definition of an
extension, as identified by extnID must include a definition of the
syntax and semantics of the extension.
6. Security considerations
6.1 Protection of Private Key
The security of the electronic signature mechanism defined in this
document depends on the privacy of the signer's private key.
Implementations must take steps to ensure that private keys cannot be
compromised.
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6.2 Choice of Algorithms
Implementers should be aware that cryptographic algorithms become
weaker with time. As new cryptoanalysis techniques are developed and
computing performance improves, the work factor to break a particular
cryptographic algorithm will reduce. Therefore, cryptographic algorithm
implementations should be modular allowing new algorithms to be readily
inserted. That is, implementers should be prepared for the set of
mandatory to implement algorithms to change over time.
7. Conformance Requirements
This document only defines conformance requirements up to a ES with
Complete validation data (ES-C). This means that none of the extended
and archive forms of Electronic Signature (ES-X, ES-A) need to be
implemented to get conformance to this standard.
This document mandates support for elements of the signature policy.
7.1 Signer
A system supporting signers according to this document must, at a
minimum, support generation of an electronic signature consisting of
the following components:
* The general CMS syntax and content type as defined in RFC 2630
(see clauses 4.1 and 4.2).
* CMS SignedData as defined in RFC 2630 with version set to 3
and at least one SignerInfo must be present
(see clauses 4.3, 4.4, 4.5, 4.6).
* The following CMS Attributes as defined in RFC 2630 :
- ContentType; This must always be present
(see clause 3.7.1);
- MessageDigest; This must always be present
(see clause 3.7.2);
- SigningTime; This must always be present
(see clause 3.7.3).
* The following ESS Attributes as defined in RFC 2634 :
- SigningCertificate: This must be set as defined
in clauses 3.8.1 and 3.8.2.
* The following Attributes as defined in clause 3.9:
- SignaturePolicyIdentifier; This must always be present.
* Public Key Certificates as defined in ITU-T Recommendation
X.509 [1] and profiled in RFC 2459 [7] (see clause 9.1).
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7.2 Verifier
A system supporting verifiers according to this document must, at a
minimum, support:
* Verification of the mandated components of an electronic
signature, as defined in clause 14.1.
* Signature Timestamp attribute, as defined in clause 5.1.1.
* Complete Certificate Refs attribute, as defined in
clause 5.2.1.
* Complete Revocation Refs Attribute, as defined in
clause 5.2.2.
* Public Key Certificates, as defined in ITU-T
Recommendation X.509 and profiled in RFC 2459
(see clause 10.1)
* Either of:
- Certificate Revocation Lists. as defined in ITU-T
Recommendation X.509 [1] and profiled in RFC 2459 [7]
(see clause 10.2); Or
- On-line Certificate Status Protocol, as defined in
RFC 2560 (see clause 10.3).
7.3 Signature Policy
Both signer and verifier systems must be able to process an electronic
signature in accordance with the specification of at least one
signature policy, as identified by the signature policy attribute
(see clause 4.9.1).
8. References
[RFC2510] C. Adams, S. Farrell, "Internet X.509 Public Key
Infrastructure, Certificate Management Protocols," RFC 2510, March 1999.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2246] T. Dierks, C. Allen, "The TLS Protocol, Version 1.0," RFC
2246, January 1999.
[RFC 2634] P. Hoffman, "Enhanced Security Services for S/MIME",
[RFC 2630] R. Housley, "Cryptographic Message Syntax", RFC 2630, June
1999.
ETSI TC-SEC, Ross, Pinkas, Pope Informational RFC [Page 52]
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[RFC2459] R. Housley, W. Ford, W. Polk, D. Solo, "Internet X.509 Public
Key Infrastructure, Certificate and CRL Profile," RFC 2459, January
1999.
[PKCS9] RSA Laboratories, "The Public-Key Cryptography Standards
(PKCS)", RSA Data Security Inc., Redwood City, California, November
1993 Release.
[ISONR] ISO/IEC 10181-5: Security Frameworks in Open Systems.
Non-Repudiation Framework. April 1997.
9. Authors' Addresses
This Informational RFC has been produced in ETSI TC-SEC.
ETSI
F-06921 Sophia Antipolis, Cedex - FRANCE
650 Route des Lucioles - Sophia Antipolis
Valbonne - France
Tel: +33 4 92 94 42 00 Fax: +33 4 93 65 47 16
secretariat@etsi.fr
http://www.etsi.org
ETSI Contact Point
Harri Rasilainen
ETSI
F-06921 Sophie Antipolis
650 Route des Lucioles
Sophia Antipolis, Valbonne
FRANCE
harri.rasilainen@etsi.fr
Additional Contact Points
John Ross
Security & Standards
192 Moulsham Street
Chelmsford, Essex
CM2 0LG
United Kingdom
ross@secstan.com
Denis Pinkas Nick Pope
Bull S.A. Security & Standards
12, rue de Paris 192 Moulsham Street
B.P. 59 Chelmsford, Essex
78231 Le Pecq CM2 0LG
FRANCE United Kingdom
pinkas.denis@bull.net pope@secstan.com
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10. Full Copyright Statement
Copyright (C) The Internet Society (2000). All Rights Reserved.
This document and translations of it may be copied and furnished to others,
and derivative works that comment on or otherwise explain it or assist in
its implementation may be prepared, copied, published and distributed, in
whole or in part, without restriction of any kind, provided that the above
copyright notice and this paragraph are included on all such copies and
derivative works. However, this document itself may not be modified in any
way, such as by removing the copyright notice or references to the Internet
Society or other Internet organizations, except as needed for the purpose of
developing Internet standards in which case the procedures for copyrights
defined in the Internet Standards process must be followed, or as required to
translate it into languages other than English.
The limited permissions granted above are perpetual and will not be revoked
by the Internet Society or its successors or assigns.
This document and the information contained herein is provided on an
"AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT
NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION HEREIN WILL
NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR
FITNESS FOR A PARTICULAR PURPOSE.
11.Temportary Issues
It might be interesting to split this document into two RFCs, one RFC
dealing only with ES formats, the other one only with Signature
Policies. In such a case, the basis of this split will be, sections 6
and annex C will be removed from this document and placed in the another
RFC dealing with Signature policies. The signature policy ASN.1 will be
removed the current ASN.1 modules in annex A and placed in a new ASN.1
module in the other RFC dealing with Signature Policies. Opinions are
requested on this issue.
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Note: If there is a request to split this document into two RFCs, one
RFC dealing with ES formats, the other with Signature policies, then the
signature policy ASN.1 will be removed the current ASN.1 modules in
annex A and placed in a new ASN.1 module in the other RFC dealing with
Signature policies.
Annex A (normative):
ASN.1 Definitions
This annex provides a summary of all the ASN.1 syntax definitions for
new syntax defined in this document.
A.1 Definitions Using X.208 (1988) ASN.1 Syntax
NOTE: The ASN.1 module defined in clause A.1 has precedence over that
defined in Annex A-2 in the case of any conflict.
ETS-ElectronicSignature-88syntax { iso(1) member-body(2)
us(840) rsadsi(113549) pkcs(1) pkcs-9(9) smime(16) id-mod(0) 5}
DEFINITIONS EXPLICIT TAGS ::=
BEGIN
-- EXPORTS All -
IMPORTS
-- Crypographic Message Syntax (CMS): RFC 2630
ContentInfo, ContentType, id-data, id-signedData, SignedData,
EncapsulatedContentInfo,
SignerInfo, id-contentType, id-messageDigest, MessageDigest,
id-signingTime, SigningTime,
id-countersignature, Countersignature
FROM CryptographicMessageSyntax
{ iso(1) member-body(2) us(840) rsadsi(113549) pkcs(1) pkcs-9(9)
smime(16) modules(0) cms(1) }
-- ESS Defined attributes: RFC 2634
-- (Enhanced Security Services for S/MIME)
id-aa-signingCertificate, SigningCertificate, IssuerSerial,
id-aa-contentReference, ContentReference,
id-aa-contentIdentifier, ContentIdentifier
FROM ExtendedSecurityServices
{ iso(1) member-body(2) us(840) rsadsi(113549)
pkcs(1) pkcs-9(9) smime(16) modules(0) ess(2) }
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-- Internet X.509 Public Key Infrastructure
- - Certificate and CRL Profile: RFC 2459
Certificate, AlgorithmIdentifier, CertificateList, Name,
GeneralNames, GeneralName,
DirectoryString,Attribute, AttributeTypeAndValue, AttributeType,
AttributeValue,
PolicyInformation, BMPString, UTF8String
FROM PKIX1Explicit88
{iso(1) identified-organization(3) dod(6) internet(1)
security(5) mechanisms(5) pkix(7) id-mod(0) id-pkix1-explicit-
88(1)}
-- X.509 '97 Authentication Framework
AttributeCertificate
FROM AuthenticationFramework
{joint-iso-ccitt ds(5) module(1) authenticationFramework(7) 3}
-- The imported AttributeCertificate is defined using the X.680 1997
-- ASN.1 Syntax,
-- an equivalent using the 88 ASN.1 syntax may be used.
-- OCSP 2560
BasicOCSPResponse, ResponderID
FROM OCSP {-- OID not assigned -- }
-- Time Stamp Protocol Internet Draft
-- TimeStampToken
FROM TSP {-- OID not assigned -- };
-- S/MIME Object Identifier arcs used in this document
-- ==================================================================
-- S/MIME OID arc used in this document
-- id-smime OBJECT IDENTIFIER ::= { iso(1) member-body(2)
-- us(840) rsadsi(113549) pkcs(1) pkcs-9(9) 16 }
-- S/MIME Arcs
-- id-mod OBJECT IDENTIFIER ::= { id-smime 0 }
-- modules
-- id-ct OBJECT IDENTIFIER ::= { id-smime 1 }
-- content types
-- id-aa OBJECT IDENTIFIER ::= { id-smime 2 }
-- attributes
-- id-spq OBJECT IDENTIFIER ::= { id-smime 5 }
-- signature policy qualifier
-- id-cti OBJECT IDENTIFIER ::= { id-smime 6 }
-- commitment type identifier
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-- Definitions of Object Identifier arcs used in this document
-- ==================================================================
-- The allocation of OIDs to specific objects are given below with the
-- associated ASN.1 syntax definition
-- OID used referencing electronic signature mechanisms based on this
-- standard for use with the IDUP API (see annex D)
id-etsi-es-IDUP-Mechanism-v1 OBJECT IDENTIFIER ::=
{ itu-t(0) identified-organization(4) etsi(0)
electronic-signature-standard (1733) part1 (1)
idupMechanism (4)etsiESv1(1) }
-- CMS Attributes Defined in this document
-- ==============================================
-- Mandatory Electronic Signature Attributes
-- OtherSigningCertificate
id-aa-ets-otherSigCert OBJECT IDENTIFIER ::= { iso(1)
member-body(2) us(840) rsadsi(113549) pkcs(1) pkcs9(9)
smime(16) id-aa(2) 19 }
OtherSigningCertificate ::= SEQUENCE {
certs SEQUENCE OF OtherCertID,
policies SEQUENCE OF PolicyInformation OPTIONAL
-- NOT USED IN THIS DOCUMENT
}
OtherCertID ::= SEQUENCE {
otherCertHash OtherHash,
issuerSerial IssuerSerial OPTIONAL }
OtherHash ::= CHOICE {
sha1Hash OtherHashValue, -- This contains a SHA-1 hash
otherHash OtherHashAlgAndValue}
OtherHashValue ::= OCTET STRING
OtherHashAlgAndValue ::= SEQUENCE {
hashAlgorithm AlgorithmIdentifier,
hashValue OtherHashValue }
-- Signature Policy Identifier
id-aa-ets-sigPolicyId OBJECT IDENTIFIER ::= { iso(1)
member-body(2) us(840) rsadsi(113549) pkcs(1) pkcs9(9)
smime(16) id-aa(2) 15 }
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SignaturePolicyIdentifier ::= SEQUENCE {
sigPolicyIdentifier SigPolicyId,
sigPolicyHash SigPolicyHash,
sigPolicyQualifiers SEQUENCE SIZE (1..MAX) OF
SigPolicyQualifierInfo OPTIONAL}
SigPolicyId ::= OBJECT IDENTIFIER
SigPolicyHash ::= ETSIHashAlgAndValue
SigPolicyQualifierInfo ::= SEQUENCE {
sigPolicyQualifierId SigPolicyQualifierId,
sigQualifier ANY DEFINED BY sigPolicyQualifierId }
SigPolicyQualifierId ::=
OBJECT IDENTIFIER
id-spq-ets-uri OBJECT IDENTIFIER ::= { iso(1)
member-body(2) us(840) rsadsi(113549) pkcs(1) pkcs9(9)
smime(16) id-spq(5) 1 }
SPuri ::= IA5String
id-spq-ets-unotice OBJECT IDENTIFIER ::= { iso(1)
member-body(2) us(840) rsadsi(113549) pkcs(1) pkcs9(9)
smime(16) id-spq(5) 2 }
SPUserNotice ::= SEQUENCE {
noticeRef NoticeReference OPTIONAL,
explicitText DisplayText OPTIONAL}
NoticeReference ::= SEQUENCE {
organization DisplayText,
noticeNumbers SEQUENCE OF INTEGER }
DisplayText ::= CHOICE {
visibleString VisibleString (SIZE (1..200)),
bmpString BMPString (SIZE (1..200)),
utf8String UTF8String (SIZE (1..200)) }
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-- Optional Electronic Signature Attributes
-- Commitment Type
id-aa-ets-commitmentType OBJECT IDENTIFIER ::= { iso(1) member-body(2)
us(840) rsadsi(113549) pkcs(1) pkcs-9(9) smime(16) id-aa(2) 16}
CommitmentTypeIndication ::= SEQUENCE {
commitmentTypeId CommitmentTypeIdentifier,
commitmentTypeQualifier SEQUENCE SIZE (1..MAX) OF
CommitmentTypeQualifier
OPTIONAL}
CommitmentTypeIdentifier ::= OBJECT IDENTIFIER
CommitmentTypeQualifier ::= SEQUENCE {
commitmentTypeIdentifier CommitmentTypeIdentifier,
qualifier ANY DEFINED BY commitmentTypeIdentifier }
id-cti-ets-proofOfOrigin OBJECT IDENTIFIER ::= { iso(1) member-
body(2) us(840) rsadsi(113549) pkcs(1) pkcs-9(9) smime(16)
cti(6) 1}
id-cti-ets-proofOfReceipt OBJECT IDENTIFIER ::= { iso(1) member-
body(2) us(840) rsadsi(113549) pkcs(1) pkcs-9(9) smime(16)
cti(6) 2}
id-cti-ets-proofOfDelivery OBJECT IDENTIFIER ::= { iso(1) member-
body(2) us(840) rsadsi(113549) pkcs(1) pkcs-9(9) smime(16)
cti(6) 3}
id-cti-ets-proofOfSender OBJECT IDENTIFIER ::= { iso(1) member-
body(2) us(840) rsadsi(113549) pkcs(1) pkcs-9(9) smime(16)
cti(6) 4}
id-cti-ets-proofOfApproval OBJECT IDENTIFIER ::= { iso(1) member-
body(2) us(840) rsadsi(113549) pkcs(1) pkcs-9(9) smime(16)
cti(6) 5}
id-cti-ets-proofOfCreation OBJECT IDENTIFIER ::= { iso(1) member-
body(2) us(840) rsadsi(113549) pkcs(1) pkcs-9(9) smime(16)
cti(6) 6}
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-- Signer Location
id-aa-ets-signerLocation OBJECT IDENTIFIER ::= { iso(1) member-body(2)
us(840) rsadsi(113549) pkcs(1) pkcs-9(9) smime(16) id-aa(2) 17}
SignerLocation ::= SEQUENCE {
-- At least one of the following must be present
countryName [0] DirectoryString OPTIONAL,
-- As used to name a Country in X.500
localityName [1] DirectoryString OPTIONAL,
-- As used to name a locality in X.500
postalAdddress [2] PostalAddress OPTIONAL }
PostalAddress ::= SEQUENCE SIZE(1..6) OF DirectoryString
-- Signer Attributes
id-aa-ets-signerAttr OBJECT IDENTIFIER ::= { iso(1) member-body(2)
us(840) rsadsi(113549) pkcs(1) pkcs-9(9) smime(16) id-aa(2) 18}
SignerAttribute ::= SEQUENCE OF CHOICE {
claimedAttributes [0] ClaimedAttributes,
certifiedAttributes [1] CertifiedAttributes }
ClaimedAttributes ::= SEQUENCE OF Attribute
CertifiedAttributes ::= AttributeCertificate -- As defined in X.509 :
see section 10.3
-- Content Timestamp
id-aa-ets-contentTimestamp OBJECT IDENTIFIER ::= { iso(1) member-
body(2) us(840) rsadsi(113549) pkcs(1) pkcs-9(9) smime(16)
id-aa(2) 20}
ContentTimestamp::= TimeStampToken
-- Validation Data
-- Signature Timestamp
id-aa-signatureTimeStampToken OBJECT IDENTIFIER ::= { iso(1) member-
body(2) us(840) rsadsi(113549) pkcs(1) pkcs-9(9) smime(16)
id-aa(2) 14}
SignatureTimeStampToken ::= TimeStampToken
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-- Complete Certificate Refs.
id-aa-ets-certificateRefs OBJECT IDENTIFIER ::= { iso(1) member-body(2)
us(840) rsadsi(113549) pkcs(1) pkcs-9(9) smime(16) id-aa(2) 21}
CompleteCertificateRefs ::= SEQUENCE OF ETSICertID
-- Complete Revocation Refs
id-aa-ets-revocationRefs OBJECT IDENTIFIER ::= { iso(1) member-body(2)
us(840) rsadsi(113549) pkcs(1) pkcs-9(9) smime(16) id-aa(2) 22}
CompleteRevocationRefs ::= SEQUENCE OF CrlOcspRef
CrlOcspRef ::= SEQUENCE {
crlids [0] CRLListID OPTIONAL,
ocspids [1] OcspListID OPTIONAL,
otherRev [2] OtherRevRefs OPTIONAL
}
CRLListID ::= SEQUENCE {
crls SEQUENCE OF CrlValidatedID}
CrlValidatedID ::= SEQUENCE {
crlHash ETSIHash,
crlIdentifier CrlIdentifier OPTIONAL}
CrlIdentifier ::= SEQUENCE {
crlissuer Name,
crlIssuedTime UTCTime,
crlNumber INTEGER OPTIONAL
}
OcspListID ::= SEQUENCE {
ocspResponses SEQUENCE OF OcspResponsesID}
OcspResponsesID ::= SEQUENCE {
ocspIdentifier OcspIdentifier,
ocspRepHash ETSIHash OPTIONAL
}
OcspIdentifier ::= SEQUENCE {
ocspResponderID ResponderID,
-- As in OCSP response data
producedAt GeneralizedTime
-- As in OCSP response data
}
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OtherRevRefs ::= SEQUENCE {
otherRevRefType OtherRevRefType,
otherRevRefs ANY DEFINED BY otherRevRefType
}
OtherRevRefType ::= OBJECT IDENTIFIER
-- Certificate Values
id-aa-ets-certValues OBJECT IDENTIFIER ::= { iso(1) member-body(2)
us(840) rsadsi(113549) pkcs(1) pkcs-9(9) smime(16) id-aa(2) 23}
CertificateValues ::= SEQUENCE OF Certificate
-- Certificate Revocation Values
id-aa-ets-revocationValues OBJECT IDENTIFIER ::= { iso(1) member-
body(2) us(840) rsadsi(113549) pkcs(1) pkcs-9(9) smime(16)
id-aa(2) 24}
RevocationValues ::= SEQUENCE {
crlVals [0] SEQUENCE OF CertificateList OPTIONAL,
ocspVals [1] SEQUENCE OF BasicOCSPResponse OPTIONAL,
otherRevVals [2] OtherRevVals }
OtherRevVals ::= SEQUENCE {
otherRevValType OtherRevValType,
otherRevVals ANY DEFINED BY otherRevValType
}
OtherRevValType ::= OBJECT IDENTIFIER
-- ES-C Timestamp
id-aa-ets-escTimeStamp OBJECT IDENTIFIER ::= { iso(1) member-body(2)
us(840) rsadsi(113549) pkcs(1) pkcs-9(9) smime(16) id-aa(2) 25}
ESCTimeStampToken ::= TimeStampToken
-- Time-Stamped Certificates and CRLs
id-aa-ets-certCRLTimestamp OBJECT IDENTIFIER ::= { iso(1) member-
body(2) us(840) rsadsi(113549) pkcs(1) pkcs-9(9) smime(16)
id-aa(2) 26}
TimestampedCertsCRLs ::= TimeStampToken
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-- Archive Timestamp
id-aa-ets-archiveTimestamp OBJECT IDENTIFIER ::= { iso(1) member-
body(2) us(840) rsadsi(113549) pkcs(1) pkcs-9(9) smime(16)
id-aa(2) 27}
ArchiveTimeStampToken ::= TimeStampToken
-- Signature Policy Specification
-- ==============================
SignaturePolicy ::= SEQUENCE {
signPolicyHashAlg AlgorithmIdentifier,
signPolicyInfo SignPolicyInfo,
signPolicyHash SignPolicyHash OPTIONAL }
SignPolicyHash ::= OCTET STRING
SignPolicyInfo ::= SEQUENCE {
signPolicyIdentifier SignPolicyId,
dateOfIssue GeneralizedTime,
policyIssuerName PolicyIssuerName,
fieldOfApplication FieldOfApplication,
signatureValidationPolicy SignatureValidationPolicy,
signPolExtensions SignPolExtensions
OPTIONAL
}
SignPolicyId ::= OBJECT IDENTIFIER
PolicyIssuerName ::= GeneralNames
FieldOfApplication ::= DirectoryString
SignatureValidationPolicy ::= SEQUENCE {
signingPeriod SigningPeriod,
commonRules CommonRules,
commitmentRules CommitmentRules,
signPolExtensions SignPolExtensions
OPTIONAL
}
SigningPeriod ::= SEQUENCE {
notBefore GeneralizedTime,
notAfter GeneralizedTime OPTIONAL }
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CommonRules ::= SEQUENCE {
signerAndVeriferRules [0] SignerAndVerifierRules
OPTIONAL,
signingCertTrustCondition [1] SigningCertTrustCondition
OPTIONAL,
timeStampTrustCondition [2] TimestampTrustCondition
OPTIONAL,
attributeTrustCondition [3] AttributeTrustCondition
OPTIONAL,
algorithmConstraintSet [4] AlgorithmConstraintSet
OPTIONAL,
signPolExtensions [5] SignPolExtensions
OPTIONAL
}
CommitmentRules ::= SEQUENCE OF CommitmentRule
CommitmentRule ::= SEQUENCE {
selCommitmentTypes SelectedCommitmentTypes,
signerAndVeriferRules [0] SignerAndVerifierRules
OPTIONAL,
signingCertTrustCondition [1] SigningCertTrustCondition
OPTIONAL,
timeStampTrustCondition [2] TimestampTrustCondition
OPTIONAL,
attributeTrustCondition [3] AttributeTrustCondition
OPTIONAL,
algorithmConstraintSet [4] AlgorithmConstraintSet
OPTIONAL,
signPolExtensions [5] SignPolExtensions
OPTIONAL
}
SelectedCommitmentTypes ::= SEQUENCE OF CHOICE {
empty NULL,
recognizedCommitmentType CommitmentType }
CommitmentType ::= SEQUENCE {
identifier CommitmentTypeIdentifier,
fieldOfApplication [0] FieldOfApplication OPTIONAL,
semantics [1] DirectoryString OPTIONAL }
SignerAndVerifierRules ::= SEQUENCE {
signerRules SignerRules,
verifierRules VerifierRules }
ETSI TC-SEC, Ross, Pinkas, Pope Informational RFC [Page 64]
Internet Draft Electronic Signature Formats
SignerRules ::= SEQUENCE {
externalSignedData BOOLEAN OPTIONAL,
-- True if signed data is external to CMS structure
-- False if signed data part of CMS structure
-- not present if either allowed
mandatedSignedAttr CMSAttrs,
-- Mandated CMS signed attributes
mandatedUnsignedAttr CMSAttrs,
-- Mandated CMS unsigned attributed
mandatedCertificateRef [0] CertRefReq DEFAULT signerOnly,
-- Mandated Certificate Reference
mandatedCertificateInfo [1] CertInfoReq DEFAULT none,
-- Mandated Certificate Info
signPolExtensions [2] SignPolExtensions
OPTIONAL}
CMSAttrs ::= SEQUENCE OF OBJECT IDENTIFIER
CertRefReq ::= ENUMERATED {
signerOnly (1),
-- Only reference to signer cert mandated
fullPath (2)
-- References for full cert path up to a trust point required
}
CertInfoReq ::= ENUMERATED {
none (0),
-- No mandatory requirements
signerOnly (1),
-- Only reference to signer cert mandated
fullPath (2)
-- References for full cert path up to a trust point mandated
}
VerifierRules ::= SEQUENCE {
mandatedUnsignedAttr MandatedUnsignedAttr,
signPolExtensions SignPolExtensions OPTIONAL
}
MandatedUnsignedAttr ::= CMSAttrs
-- Mandated CMS unsigned attributed
ETSI TC-SEC, Ross, Pinkas, Pope Informational RFC [Page 65]
Internet Draft Electronic Signature Formats
CertificateTrustTrees ::= SEQUENCE OF CertificateTrustPoint
CertificateTrustPoint ::= SEQUENCE {
trustpoint Certificate,
-- self-signed certificate
pathLenConstraint [0] PathLenConstraint OPTIONAL,
acceptablePolicySet [1] AcceptablePolicySet OPTIONAL,
-- If not present "any policy"
nameConstraints [2] NameConstraints OPTIONAL,
policyConstraints [3] PolicyConstraints OPTIONAL }
PathLenConstraint ::= INTEGER (0..MAX)
AcceptablePolicySet ::= SEQUENCE OF CertPolicyId
CertPolicyId ::= OBJECT IDENTIFIER
NameConstraints ::= SEQUENCE {
permittedSubtrees [0] GeneralSubtrees OPTIONAL,
excludedSubtrees [1] GeneralSubtrees OPTIONAL }
GeneralSubtrees ::= SEQUENCE SIZE (1..MAX) OF GeneralSubtree
GeneralSubtree ::= SEQUENCE {
base GeneralName,
minimum [0] BaseDistance DEFAULT 0,
maximum [1] BaseDistance OPTIONAL }
BaseDistance ::= INTEGER (0..MAX)
PolicyConstraints ::= SEQUENCE {
requireExplicitPolicy [0] SkipCerts OPTIONAL,
inhibitPolicyMapping [1] SkipCerts OPTIONAL }
SkipCerts ::= INTEGER (0..MAX)
CertRevReq ::= SEQUENCE {
endCertRevReq RevReq,
caCerts [0] RevReq
}
RevReq ::= SEQUENCE {
enuRevReq EnuRevReq,
exRevReq SignPolExtensions OPTIONAL}
ETSI TC-SEC, Ross, Pinkas, Pope Informational RFC [Page 66]
Internet Draft Electronic Signature Formats
EnuRevReq ::= ENUMERATED {
clrCheck (0), --Checks must be made against current CRLs
-- (or authority revocation lists)
ocspCheck (1), -- The revocation status must be checked
-- using the Online Certificate Status Protocol (RFC 2450)
bothCheck (2),
-- Both CRL and OCSP checks must be carried out
eitherCheck (3),
-- At least one of CRL or OCSP checks must be carried out
noCheck (4),
-- no check is mandated
other (5)
-- Other mechanism as defined by signature policy extension
}
SigningCertTrustCondition ::= SEQUENCE {
signerTrustTrees CertificateTrustTrees,
signerRevReq CertRevReq
}
TimestampTrustCondition ::= SEQUENCE {
ttsCertificateTrustTrees [0] CertificateTrustTrees
OPTIONAL,
ttsRevReq [1] CertRevReq
OPTIONAL,
ttsNameConstraints [2] NameConstraints
OPTIONAL,
cautionPeriod [3] DeltaTime
OPTIONAL,
signatureTimestampDelay [4] DeltaTime
OPTIONAL }
DeltaTime ::= SEQUENCE {
deltaSeconds INTEGER,
deltaMinutes INTEGER,
deltaHours INTEGER,
deltaDays INTEGER }
AttributeTrustCondition ::= SEQUENCE {
attributeMandated BOOLEAN,
-- Attribute must be present
howCertAttribute HowCertAttribute,
attrCertificateTrustTrees [0] CertificateTrustTrees OPTIONAL,
attrRevReq [1] CertRevReq OPTIONAL,
attributeConstraints [2] AttributeConstraints OPTIONAL }
HowCertAttribute ::= ENUMERATED {
claimedAttribute (0),
certifiedAttribtes (1),
either (2) }
ETSI TC-SEC, Ross, Pinkas, Pope Informational RFC [Page 67]
Internet Draft Electronic Signature Formats
AttributeConstraints ::= SEQUENCE {
attributeTypeConstarints [0] AttributeTypeConstraints
OPTIONAL,
attributeValueConstarints [1] AttributeValueConstraints
OPTIONAL }
AttributeTypeConstraints ::= SEQUENCE OF AttributeType
AttributeValueConstraints ::= SEQUENCE OF AttributeTypeAndValue
AlgorithmConstraintSet ::= SEQUENCE { -- Algorithm constrains on:
signerAlgorithmConstraints [0] AlgorithmConstraints OPTIONAL,
-- signer
eeCertAlgorithmConstraints [1] AlgorithmConstraints OPTIONAL,
-- issuer of end entity certs.
caCertAlgorithmConstraints [2] AlgorithmConstraints OPTIONAL,
-- issuer of CA certificates
aaCertAlgorithmConstraints [3] AlgorithmConstraints OPTIONAL,
-- Attribute Authority
tsaCertAlgorithmConstraints [4] AlgorithmConstraints OPTIONAL
-- TimeStamping Authority
}
AlgorithmConstraints ::= SEQUENCE OF AlgAndLength
AlgAndLength ::= SEQUENCE {
algID OBJECT IDENTIFIER,
minKeyLength INTEGER OPTIONAL,
-- Minimum key length in bits other
SignPolExtensions OPTIONAL
}
SignPolExtensions ::= SEQUENCE OF SignPolExtn
SignPolExtn ::= SEQUENCE {
extnID OBJECT IDENTIFIER,
extnValue OCTET STRING }
END -- ETS-ElectronicSignature-88syntax --
ETSI TC-SEC, Ross, Pinkas, Pope Informational RFC [Page 68]
Internet Draft Electronic Signature Formats
A.2 Definitions Using X.680 1997 ASN.1 Syntax
NOTE: The ASN.1 module defined in clause A.1 has precedence over that
defined in clause A.2 in the case of any conflict.
ETS-ElectronicSignature-97Syntax { iso(1) member-body(2)
us(840) rsadsi(113549) pkcs(1) pkcs-9(9) smime(16) id-mod(0) 6}
DEFINITIONS EXPLICIT TAGS ::=
BEGIN
-- EXPORTS All -
IMPORTS
-- Crypographic Message Syntax (CMS): RFC 2630
ContentInfo, ContentType, id-data, id-signedData, SignedData,
EncapsulatedContentInfo, SignerInfo,
id-contentType, id-messageDigest, MessageDigest, id-signingTime,
SigningTime, id-countersignature, Countersignature
FROM CryptographicMessageSyntax
{ iso(1) member-body(2) us(840) rsadsi(113549) pkcs(1) pkcs-9(9)
smime(16) modules(0) cms(1) }
-- ESS Defined attributes: RFC 2634 (Enhanced Security Services
-- for S/MIME)
id-aa-signingCertificate, SigningCertificate, IssuerSerial,
id-aa-contentReference, ContentReference,
id-aa-contentIdentifier, ContentIdentifier
FROM ExtendedSecurityServices
{ iso(1) member-body(2) us(840) rsadsi(113549)
pkcs(1) pkcs-9(9) smime(16) modules(0) ess(2) }
-- Internet X.509 Public Key Infrastructure
- - Certificate and CRL Profile:RFC 2459
Certificate, AlgorithmIdentifier, CertificateList, Name,
GeneralNames, GeneralName, DirectoryString, Attribute,
AttributeTypeAndValue, AttributeType, AttributeValue,
PolicyInformation.
FROM PKIX1Explicit93
{iso(1) identified-organization(3) dod(6) internet(1)
security(5) mechanisms(5) pkix(7) id-mod(0)
id-pkix1-explicit-88(1)}
-- X.509 '97 Authentication Framework
AttributeCertificate
FROM AuthenticationFramework
{joint-iso-ccitt ds(5) module(1) authenticationFramework(7) 3}
ETSI TC-SEC, Ross, Pinkas, Pope Informational RFC [Page 69]
Internet Draft Electronic Signature Formats
-- OCSP 2560
BasicOCSPResponse, ResponderID
FROM OCSP
-- { OID not assigned }
-- Time Stamp Protocol Internet Draft TimeStampToken
FROM TSP
-- { OID not assigned };
-- S/MIME Object Identifier arcs used in this document
-- ==================================================================
-- S/MIME OID arc used in this document
-- id-smime OBJECT IDENTIFIER ::= { iso(1) member-body(2)
-- us(840) rsadsi(113549) pkcs(1) pkcs-9(9) 16 }
-- S/MIME Arcs
-- id-mod OBJECT IDENTIFIER ::= { id-smime 0 }
-- modules
-- id-ct OBJECT IDENTIFIER ::= { id-smime 1 }
-- content types
-- id-aa OBJECT IDENTIFIER ::= { id-smime 2 }
-- attributes
-- id-spq OBJECT IDENTIFIER ::= { id-smime 5 }
-- signature policy qualifier
-- id-cti OBJECT IDENTIFIER ::= { id-smime 6 }
-- commitment type identifier
-- Definitions of Object Identifier arcs used in this document
-- ==================================================================
-- The allocation of OIDs to specific objects are given below with the
-- associated ASN.1 syntax definition
-- OID used referencing electronic signature mechanisms based on this
-- standard for use with the IDUP API (see annex D)
id-etsi-es-IDUP-Mechanism-v1 OBJECT IDENTIFIER ::=
{ itu-t(0) identified-organization(4) etsi(0)
electronic-signature-standard (1733) part1 (1)
idupMechanism (4)etsiESv1(1) }
ETSI TC-SEC, Ross, Pinkas, Pope Informational RFC [Page 70]
Internet Draft Electronic Signature Formats
-- CMS Attributes Defined in this document
-- ==============================================
-- Mandatory Electronic Signature Attributes
-- OtherSigningCertificate
id-aa-ets-otherSigCert OBJECT IDENTIFIER ::= { iso(1)
member-body(2) us(840) rsadsi(113549) pkcs(1) pkcs9(9)
smime(16) id-aa(2) 19 }
OtherSigningCertificate ::= SEQUENCE {
certs SEQUENCE OF OtherCertID,
policies SEQUENCE OF PolicyInformation OPTIONAL
-- NOT USED IN THIS DOCUMENT
}
OtherCertID ::= SEQUENCE {
otherCertHash OtherHash,
issuerSerial IssuerSerial OPTIONAL }
OtherHash ::= CHOICE {
sha1Hash OtherHashValue, -- This contains a SHA-1 hash
otherHash OtherHashAlgAndValue}
OtherHashValue ::= OCTET STRING
OtherHashAlgAndValue ::= SEQUENCE {
hashAlgorithm AlgorithmIdentifier,
hashValue OtherHashValue }
-- Signature Policy Identifier
id-aa-ets-sigPolicyId OBJECT IDENTIFIER ::= { iso(1)
member-body(2) us(840) rsadsi(113549) pkcs(1) pkcs9(9)
smime(16) id-aa(2) 15 }
SignaturePolicyIdentifier ::= SEQUENCE {
sigPolicyIdentifier SigPolicyId,
sigPolicyHash SigPolicyHash,
sigPolicyQualifiers SEQUENCE SIZE (1..MAX) OF
SigPolicyQualifierInfo OPTIONAL}
ETSI TC-SEC, Ross, Pinkas, Pope Informational RFC [Page 71]
Internet Draft Electronic Signature Formats
SigPolicyId ::= OBJECT IDENTIFIER
SigPolicyHash ::= ETSIHashAlgAndValue
SigPolicyQualifierInfo ::= SEQUENCE {
sigPolicyQualifierId SIG-POLICY-QUALIFIER.&id
({SupportedSigPolicyQualifiers}),
qualifier SIG-POLICY-QUALIFIER.&Qualifier
({SupportedSigPolicyQualifiers}
{@sigPolicyQualifierId})OPTIONAL }
SupportedSigPolicyQualifiers SIG-POLICY-QUALIFIER ::=
{ noticeToUser | pointerToSigPolSpec }
SIG-POLICY-QUALIFIER ::= CLASS {
&id OBJECT IDENTIFIER UNIQUE,
&Qualifier OPTIONAL }
WITH SYNTAX {
SIG-POLICY-QUALIFIER-ID &id
[SIG-QUALIFIER-TYPE &Qualifier] }
noticeToUser SIG-POLICY-QUALIFIER ::= {
SIG-POLICY-QUALIFIER-ID id-sqt-unotice SIG-QUALIFIER-TYPE
SPUserNotice
}
pointerToSigPolSpec SIG-POLICY-QUALIFIER ::= {
SIG-POLICY-QUALIFIER-ID id-sqt-uri SIG-QUALIFIER-TYPE SPuri }
id-spq-ets-uri OBJECT IDENTIFIER ::= { iso(1)
member-body(2) us(840) rsadsi(113549) pkcs(1) pkcs9(9)
smime(16) id-spq(5) 1 }
SPuri ::= IA5String
id-spq-ets-unotice OBJECT IDENTIFIER ::= { iso(1)
member-body(2) us(840) rsadsi(113549) pkcs(1) pkcs9(9)
smime(16) id-spq(5) 2 }
SPUserNotice ::= SEQUENCE {
noticeRef NoticeReference OPTIONAL,
explicitText DisplayText OPTIONAL}
NoticeReference ::= SEQUENCE {
organization DisplayText,
noticeNumbers SEQUENCE OF INTEGER }
DisplayText ::= CHOICE {
visibleString VisibleString (SIZE (1..200)),
bmpString BMPString (SIZE (1..200)),
utf8String UTF8String (SIZE (1..200)) }
ETSI TC-SEC, Ross, Pinkas, Pope Informational RFC [Page 72]
Internet Draft Electronic Signature Formats
-- Optional Electronic Signature Attributes
-- Commitment Type
id-aa-ets-commitmentType OBJECT IDENTIFIER ::= { iso(1) member-body(2)
us(840) rsadsi(113549) pkcs(1) pkcs-9(9) smime(16) id-aa(2) 16}
CommitmentTypeIndication ::= SEQUENCE {
commitmentTypeId CommitmentTypeIdentifier,
commitmentTypeQualifier SEQUENCE SIZE (1..MAX) OF
CommitmentTypeQualifier
OPTIONAL}
CommitmentTypeIdentifier ::= OBJECT IDENTIFIER
CommitmentTypeQualifier ::= SEQUENCE {
commitmentQualifierId COMMITMENT-QUALIFIER.&id,
qualifier COMMITMENT-QUALIFIER.&Qualifier
OPTIONAL }
COMMITMENT-QUALIFIER ::= CLASS {
&id OBJECT IDENTIFIER UNIQUE,
&Qualifier OPTIONAL }
WITH SYNTAX {
COMMITMENT-QUALIFIER-ID &id
[COMMITMENT-TYPE &Qualifier] }
id-cti-ets-proofOfOrigin OBJECT IDENTIFIER ::= { iso(1)
member-body(2) us(840) rsadsi(113549) pkcs(1) pkcs-9(9)
smime(16) cti(6) 1}
id-cti-ets-proofOfReceipt OBJECT IDENTIFIER ::= { iso(1)
member-body(2) us(840) rsadsi(113549) pkcs(1) pkcs-9(9)
smime(16) cti(6) 2}
id-cti-ets-proofOfDelivery OBJECT IDENTIFIER ::= { iso(1)
member-body(2) us(840) rsadsi(113549) pkcs(1) pkcs-9(9)
smime(16) cti(6) 3}
id-cti-ets-proofOfSender OBJECT IDENTIFIER ::= { iso(1)
member-body(2) us(840) rsadsi(113549) pkcs(1) pkcs-9(9)
smime(16) cti(6) 4}
id-cti-ets-proofOfApproval OBJECT IDENTIFIER ::= { iso(1)
member-body(2) us(840) rsadsi(113549) pkcs(1) pkcs-9(9)
smime(16) cti(6) 5}
id-cti-ets-proofOfCreation OBJECT IDENTIFIER ::= { iso(1)
member-body(2) us(840) rsadsi(113549) pkcs(1) pkcs-9(9)
smime(16) cti(6) 6}
ETSI TC-SEC, Ross, Pinkas, Pope Informational RFC [Page 73]
Internet Draft Electronic Signature Formats
-- Signer Location
id-aa-ets-signerLocation OBJECT IDENTIFIER ::= { iso(1) member-body(2)
us(840) rsadsi(113549) pkcs(1) pkcs-9(9) smime(16) id-aa(2) 17}
SignerLocation ::= SEQUENCE {
-- at least one of the following must be present
countryName [0] DirectoryString OPTIONAL,
-- As used to name a Country in X.500
localityName [1] DirectoryString OPTIONAL,
-- As used to name a locality in X.500
postalAdddress [2] PostalAddress OPTIONAL }
PostalAddress ::= SEQUENCE SIZE(1..6) OF DirectoryString
-- Signer Attributes
id-aa-ets-signerAttr OBJECT IDENTIFIER ::= { iso(1) member-body(2)
us(840) rsadsi(113549) pkcs(1) pkcs-9(9) smime(16) id-aa(2) 18}
SignerAttribute ::= SEQUENCE OF CHOICE {
claimedAttributes [0] ClaimedAttributes,
certifiedAttributes [1] CertifiedAttributes }
ClaimedAttributes ::= SEQUENCE OF Attribute
CertifiedAttributes ::= AttributeCertificate
-- As defined in X.509 : see section 10.3
-- Content Timestamp
id-aa-ets-contentTimestamp OBJECT IDENTIFIER ::= { iso(1)
member-body(2) us(840) rsadsi(113549) pkcs(1) pkcs-9(9)
smime(16) id-aa(2) 20}
ContentTimestamp::= TimeStampToken
-- Validation Data
-- Signature Timestamp
id-aa-signatureTimeStampToken OBJECT IDENTIFIER ::= { iso(1)
member-body(2) us(840) rsadsi(113549) pkcs(1) pkcs-9(9)
smime(16) id-aa(2) 14}
SignatureTimeStampToken ::= TimeStampToken
ETSI TC-SEC, Ross, Pinkas, Pope Informational RFC [Page 74]
Internet Draft Electronic Signature Formats
-- Complete Certificate Refs.
id-aa-ets-certificateRefs OBJECT IDENTIFIER ::= { iso(1) member-body(2)
us(840) rsadsi(113549) pkcs(1) pkcs-9(9) smime(16) id-aa(2) 21}
CompleteCertificateRefs ::= SEQUENCE OF ETSICertID
-- Complete Revocation Refs
id-aa-ets-revocationRefs OBJECT IDENTIFIER ::= { iso(1) member-body(2)
us(840) rsadsi(113549) pkcs(1) pkcs-9(9) smime(16) id-aa(2) 22}
CompleteRevocationRefs ::= SEQUENCE OF CrlOcspRef
CrlOcspRef ::= SEQUENCE {
crlids [0] CRLListID OPTIONAL,
ocspids [1] OcspListID OPTIONAL,
otherRev [2] OtherRevRefs OPTIONAL
}
CRLListID ::= SEQUENCE {
crls SEQUENCE OF CrlValidatedID}
CrlValidatedID ::= SEQUENCE {
crlHash ETSIHash,
crlIdentifier CrlIdentifier OPTIONAL}
CrlIdentifier ::= SEQUENCE {
crlissuer Name,
crlIssuedTime UTCTime,
crlNumber INTEGER OPTIONAL
}
OcspListID ::= SEQUENCE {
ocspResponses SEQUENCE OF OcspResponsesID}
OcspResponsesID ::= SEQUENCE {
ocspIdentifier OcspIdentifier,
ocspRepHash ETSIHash OPTIONAL
}
OcspIdentifier ::= SEQUENCE {
ocspResponderID ResponderID,
-- As in OCSP response data
producedAt GeneralizedTime
-- As in OCSP response data
}
ETSI TC-SEC, Ross, Pinkas, Pope Informational RFC [Page 75]
Internet Draft Electronic Signature Formats
OtherRevRefs ::= SEQUENCE {
otherRevRefType OTHER-REVOCATION-REF.&id,
otherRevRefs OTHER-REVOCATION-REF.&Type
}
OTHER-REVOCATION-REF ::= CLASS {
&Type,
&id OBJECT IDENTIFIER UNIQUE }
WITH SYNTAX {
&Type ID &id }
-- Certificate Values
id-aa-ets-certValues OBJECT IDENTIFIER ::= { iso(1) member-body(2)
us(840) rsadsi(113549) pkcs(1) pkcs-9(9) smime(16) id-aa(2) 23}
CertificateValues ::= SEQUENCE OF Certificate
-- Certificate Revocation Values
id-aa-ets-revocationValues OBJECT IDENTIFIER ::= { iso(1)
member-body(2)us(840) rsadsi(113549) pkcs(1) pkcs-9(9)
smime(16) id-aa(2) 24}
RevocationValues ::= SEQUENCE {
crlVals [0] SEQUENCE OF CertificateList OPTIONAL,
ocspVals [1] SEQUENCE OF BasicOCSPResponse OPTIONAL,
otherRevVals [2] OtherRevVals }
OtherRevVals ::= SEQUENCE {
otherRevValType OTHER-REVOCATION-VAL.&id,
otherRevVals OTHER-REVOCATION-VAL.&Type
}
OTHER-REVOCATION-VAL ::= CLASS {
&Type,
&id OBJECT IDENTIFIER UNIQUE }
WITH SYNTAX {
&Type ID &id }
-- ES-C Timestamp
id-aa-ets-escTimeStamp OBJECT IDENTIFIER ::= { iso(1)
member-body(2) us(840) rsadsi(113549) pkcs(1) pkcs-9(9)
smime(16) id-aa(2) 25}
ESCTimeStampToken ::= TimeStampToken
ETSI TC-SEC, Ross, Pinkas, Pope Informational RFC [Page 76]
Internet Draft Electronic Signature Formats
-- Time-Stamped Certificates and CRLs
id-aa-ets-certCRLTimestamp OBJECT IDENTIFIER ::= { iso(1)
member-body(2) us(840) rsadsi(113549) pkcs(1) pkcs-9(9)
smime(16) id-aa(2) 26}
TimestampedCertsCRLs ::= TimeStampToken
-- Archive Timestamp
id-aa-ets-archiveTimestamp OBJECT IDENTIFIER ::= { iso(1)
member-body(2)us(840) rsadsi(113549) pkcs(1) pkcs-9(9)
smime(16) id-aa(2) 27}
ArchiveTimeStampToken ::= TimeStampToken
-- Signature Policy Specification
-- ==============================
SignaturePolicy ::= SEQUENCE {
signPolicyHashAlg AlgorithmIdentifier,
signPolicyInfo SignPolicyInfo,
signPolicyHash SignPolicyHash OPTIONAL }
SignPolicyHash ::= OCTET STRING
SignPolicyInfo ::= SEQUENCE {
signPolicyIdentifier SignPolicyId,
dateOfIssue GeneralizedTime,
policyIssuerName PolicyIssuerName,
fieldOfApplication FieldOfApplication,
signatureValidationPolicy SignatureValidationPolicy,
signPolExtensions SignPolExtensions
OPTIONAL
}
SignPolicyId ::= OBJECT IDENTIFIER
PolicyIssuerName ::= GeneralNames
FieldOfApplication ::= DirectoryString
SignatureValidationPolicy ::= SEQUENCE {
signingPeriod SigningPeriod,
commonRules CommonRules,
commitmentRules CommitmentRules,
signPolExtensions SignPolExtensions OPTIONAL
}
ETSI TC-SEC, Ross, Pinkas, Pope Informational RFC [Page 77]
Internet Draft Electronic Signature Formats
SigningPeriod ::= SEQUENCE {
notBefore GeneralizedTime,
notAfter GeneralizedTime OPTIONAL }
CommonRules ::= SEQUENCE {
signerAndVeriferRules [0] SignerAndVerifierRules
OPTIONAL,
signingCertTrustCondition [1] SigningCertTrustCondition
OPTIONAL,
timeStampTrustCondition [2] TimestampTrustCondition
OPTIONAL,
attributeTrustCondition [3] AttributeTrustCondition
OPTIONAL,
algorithmConstraintSet [4] AlgorithmConstraintSet
OPTIONAL,
signPolExtensions [5] SignPolExtensions
OPTIONAL
}
CommitmentRules ::= SEQUENCE OF CommitmentRule
CommitmentRule ::= SEQUENCE {
selCommitmentTypes SelectedCommitmentTypes,
signerAndVeriferRules [0] SignerAndVerifierRules
OPTIONAL,
signingCertTrustCondition [1] SigningCertTrustCondition
OPTIONAL,
timeStampTrustCondition [2] TimestampTrustCondition
OPTIONAL,
attributeTrustCondition [3] AttributeTrustCondition
OPTIONAL,
algorithmConstraintSet [4] AlgorithmConstraintSet
OPTIONAL,
signPolExtensions [5] SignPolExtensions
OPTIONAL
}
SelectedCommitmentTypes ::= SEQUENCE OF CHOICE {
empty NULL,
recognizedCommitmentType CommitmentType }
CommitmentType ::= SEQUENCE {
identifier CommitmentTypeIdentifier,
fieldOfApplication [0] FieldOfApplication OPTIONAL,
semantics [1] DirectoryString OPTIONAL }
SignerAndVerifierRules ::= SEQUENCE {
signerRules SignerRules,
verifierRules VerifierRules }
ETSI TC-SEC, Ross, Pinkas, Pope Informational RFC [Page 78]
Internet Draft Electronic Signature Formats
SignerRules ::= SEQUENCE {
externalSignedData BOOLEAN OPTIONAL,
-- True if signed data is external to CMS structure
-- False if signed data part of CMS structure
-- not present if either allowed
mandatedSignedAttr CMSAttrs,
-- Mandated CMS signed attributes
mandatedUnsignedAttr CMSAttrs,
-- Mandated CMS unsigned attributed
mandatedCertificateRef [0] CertRefReq DEFAULT signerOnly,
-- Mandated Certificate Reference
mandatedCertificateInfo [1] CertInfoReq DEFAULT none,
-- Mandated Certificate Info
signPolExtensions [2] SignPolExtensions OPTIONAL
}
CMSAttrs ::= SEQUENCE OF OBJECT IDENTIFIER
CertRefReq ::= ENUMERATED {
signerOnly (1),
-- Only reference to signer cert mandated
fullPath (2)
-- References for full cert path up to a trust
-- point required
}
CertInfoReq ::= ENUMERATED {
none (0) ,
-- No mandatory requirements
signerOnly (1) ,
-- Only reference to signer cert mandated
fullPath (2)
-- References for full cert path up to a
-- trust point mandated
}
VerifierRules ::= SEQUENCE {
mandatedUnsignedAttr MandatedUnsignedAttr,
signPolExtensions SignPolExtensions OPTIONAL
}
MandatedUnsignedAttr ::= CMSAttrs
-- Mandated CMS unsigned attributed
ETSI TC-SEC, Ross, Pinkas, Pope Informational RFC [Page 79]
Internet Draft Electronic Signature Formats
CertificateTrustTrees ::= SEQUENCE OF CertificateTrustPoint
CertificateTrustPoint ::= SEQUENCE {
trustpoint Certificate,
-- self-signed certificate
pathLenConstraint [0] PathLenConstraint OPTIONAL,
acceptablePolicySet [1] AcceptablePolicySet OPTIONAL,
-- If not present "any policy"
nameConstraints [2] NameConstraints OPTIONAL,
policyConstraints [3] PolicyConstraints OPTIONAL }
PathLenConstraint ::= INTEGER (0..MAX)
AcceptablePolicySet ::= SEQUENCE OF CertPolicyId
CertPolicyId ::= OBJECT IDENTIFIER
NameConstraints ::= SEQUENCE {
permittedSubtrees [0] GeneralSubtrees OPTIONAL,
excludedSubtrees [1] GeneralSubtrees OPTIONAL }
GeneralSubtrees ::= SEQUENCE SIZE (1..MAX) OF GeneralSubtree
GeneralSubtree ::= SEQUENCE {
base GeneralName,
minimum [0] BaseDistance DEFAULT 0,
maximum [1] BaseDistance OPTIONAL }
BaseDistance ::= INTEGER (0..MAX)
PolicyConstraints ::= SEQUENCE {
requireExplicitPolicy [0] SkipCerts OPTIONAL,
inhibitPolicyMapping [1] SkipCerts OPTIONAL }
SkipCerts ::= INTEGER (0..MAX)
CertRevReq ::= SEQUENCE {
endCertRevReq RevReq,
caCerts [0] RevReq
}
RevReq ::= SEQUENCE {
enuRevReq EnuRevReq,
exRevReq SignPolExtensions OPTIONAL}
ETSI TC-SEC, Ross, Pinkas, Pope Informational RFC [Page 80]
Internet Draft Electronic Signature Formats
EnuRevReq ::= ENUMERATED {
clrCheck (0),
-- Checks must be made against current CRLs
-- (or authority revocation lists)
ocspCheck (1),
-- The revocation status must be checked using
-- the Online Certificate Status Protocol (RFC 2450)
bothCheck (2),
-- Both CRL and OCSP checks must be carried out
eitherCheck (3),
-- At least one of CRL or OCSP checks must be carried out
noCheck (4),
-- no check is mandated
other (5)
-- Other mechanism as defined by signature poilicy
-- extension
}
SigningCertTrustCondition ::= SEQUENCE {
signerTrustTrees CertificateTrustTrees,
signerRevReq CertRevReq
}
TimestampTrustCondition ::= SEQUENCE {
ttsCertificateTrustTrees [0] CertificateTrustTrees
OPTIONAL,
ttsRevReq [1] CertRevReq
OPTIONAL,
ttsNameConstraints [2] NameConstraints
OPTIONAL,
cautionPeriod [3] DeltaTime
OPTIONAL,
signatureTimestampDelay [4] DeltaTime
OPTIONAL }
DeltaTime ::= SEQUENCE {
deltaSeconds INTEGER,
deltaMinutes INTEGER,
deltaHours INTEGER,
deltaDays INTEGER }
AttributeTrustCondition ::= SEQUENCE {
attributeMandated BOOLEAN,
-- Attribute must be present
howCertAttribute HowCertAttribute,
attrCertificateTrustTrees [0] CertificateTrustTrees OPTIONAL,
attrRevReq [1] CertRevReq OPTIONAL,
attributeConstraints [2] AttributeConstraints OPTIONAL }
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HowCertAttribute ::= ENUMERATED {
claimedAttribute (0),
certifiedAttribtes (1),
either (2) }
AttributeConstraints ::= SEQUENCE {
attributeTypeConstarints [0] AttributeTypeConstraints
OPTIONAL,
attributeValueConstarints [1] AttributeValueConstraints
OPTIONAL }
AttributeTypeConstraints ::= SEQUENCE OF AttributeType
AttributeValueConstraints ::= SEQUENCE OF AttributeTypeAndValue
AlgorithmConstraintSet ::= SEQUENCE {
-- Algorithm constrains on:
signerAlgorithmConstraints [0] AlgorithmConstraints OPTIONAL,
-- signer
eeCertAlgorithmConstraints [1] AlgorithmConstraints OPTIONAL,
-- issuer of end entity certs.
caCertAlgorithmConstraints [2] AlgorithmConstraints OPTIONAL,
-- issuer of CA certificates
aaCertAlgorithmConstraints [3] AlgorithmConstraints OPTIONAL,
-- Attribute Authority
tsaCertAlgorithmConstraints [4] AlgorithmConstraints OPTIONAL
-- TimeStamping Authority
}
AlgorithmConstraints ::= SEQUENCE OF AlgAndLength
AlgAndLength ::= SEQUENCE {
algID OBJECT IDENTIFIER,
minKeyLength INTEGER OPTIONAL,
-- Minimum key length in bits
other SignPolExtensions OPTIONAL
}
SignPolExtensions ::= SEQUENCE OF SignPolExtn
SignPolExtn ::= SEQUENCE {
extnID OBJECT IDENTIFIER,
extnValue OCTET STRING }
END -- ETS-ElectronicSignature-97Syntax
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Annex B (informative):
General Description
This annex captures the concepts that apply to this document and the
rational for the elements of the specification defined using ASN.1 in
the main text of this document.
The specification below includes a description why the component is
needed, with a brief description of the vulnerabilities and threats and
the manner by which they are countered.
B.1 The Signature Policy
The signature policy is a set of rules for the creation and validation
of an electronic signature, under which the signature can be determined
to be valid. A given legal/contractual context may recognize a
particular signature policy as meeting its requirements. A signature
policy may be issued, for example, by a party relying on the electronic
signatures and selected by the signer for use with that relying party.
Alternatively, a signature policy may be established through an
electronic trading association for use amongst its members. Both the
signer and verifier use the same signature policy.
A signature policy has a globally unique reference, which is bound to
an electronic signature by the signer as part of the signature
calculation.
The signature policy needs to be available in human readable form so
that it can be assessed to meet the requirements of the legal and
contractual context in which it is being applied. To facilitate the
automatic processing of an electronic signature the parts of the
signature policy which specify the electronic rules for the creation
and validation of the electronic signature also needs to be in a
computer processable form.
The signature policy thus includes the following:
* Rules, which apply to functionality, covered by this document
(referred to as the Signature Validation Policy).
* Rules which may be implied through adoption of Certificate
Policies that apply to the electronic signature (e.g. rules for
ensuring the secrecy of the private signing key).
* Rules, which relate to the environment used by the signer,
e.g. the use of an agreed CAD (Card Accepting Device) used
in conjunction with a smart card.
The Signature Validation Policy may be structured so that it can be
computer processable. The current document includes, as an option, a
formal structure for the signature validation policy based on the used
of Abstract Syntax Notation 1 (ASN.1). Other formats of the signature
validation policy are allowed by this document. However, for a given
signature policy there must be one definitive form that has a unique
binary encoded value.
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The Signature Validation Policy includes rules regarding use of TSPs
(CA, Attribute Authorities, Time Stamping Authorities) as well as rules
defining the components of the electronic signature that must be
provided by the signer with data required by the verifier to provide
long term proof.
B.2 Signed Information
The information being signed may be defined as a MIME-encapsulated
message which can be used to signal the format of the content in order
to select the right display or application. It can be composed of
formatted text (e.g. EDIFACT), free text or of fields from an
electronic form (e-form). For example, the Adobe(tm) format "pdf" may
be used or the eXtensible Mark up Language (XML).
B.3 Components of an Electronic Signature
B.3.1 Reference to the Signature Policy
The definition of electronic signature includes: "a commitment has been
explicitly endorsed under a "Signature policy", at a given time, by a
signer under an identifier, e.g. a name or a pseudonym, and optionally
a role".
When two independent parties want to evaluate an electronic signature,
it is fundamental that they get the same result. To meet this
requirement the technical components and technical aspects used in
creating the signature must be referenced, this is provided by a
reference to the "Signature Validation Policy". The "Signature
Validation Policy" defines:
* the components of an electronic signature to be provided by the
signer;
* any additional components (i.e. verifier components) used to
validate an electronic signature at the time of receipt by a
verifier and later by an arbitrator, auditor or other
independent parties.
By signing over the signature policy identifier, the algorithm
identifier and the hash of the signature policy, the signer explicitly
indicates that he or she has applied the signature policy in creating
the signature. Thus, undertakes any commitments implied by the
signature policy, any indication of commitment type included in the
electronic signature, and the user data that is signed.
The hash algorithm identifier and value is included to ensure that both
the signer and verifier use exactly the same signature policy. This
unambiguously binds the signer and verifier to same definitive form of
the signature policy has a unique binary encoding.
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In order to identify unambiguously the "Signature Validation Policy" to
be used to verify the signature an identifier and hash of the
"Signature policy" must be part of the signed data. Additional
information about the policy (e.g. web reference to the document) may
be carried as "qualifiers" to the signature policy identifier
B.3.2 Commitment Type Indication
The definition of electronic signature includes: "a commitment has been
explicitly endorsed under a signature policy, at a given time, by a
signer under an identifier, e.g. a name or a pseudonym, and optionally a
role".
The commitment type can be indicated in the electronic signature
either:
* explicitly using a "commitment type indication" in the
electronic signature;
* implicitly or explicitly from the semantics of the signed data.
If the indicated commitment type is explicit using a "commitment type
indication" in the electronic signature , acceptance of a verified
signature implies acceptance of the semantics of that commitment type.
The semantics of explicit commitment types indications must be
specified either as part of the signature policy or may be registered
for generic use across multiple policies.
If a signature includes a commitment type indication other than one of
those recognized under the signature policy the signature must be
treated as invalid.
How commitment is indicated using the semantics of the data being
signed is outside the scope of this document.
NOTE: Examples of commitment indicated through the semantics of the
data being signed, are:
* An explicit commitment made by the signer indicated by the type
of data being signed over. Thus, the data structure being
signed can have an explicit commitment within the context of the
application (e.g. EDIFACT purchase order).
* An implicit commitment which is a commitment made by the signer
because the data being signed over has specific semantics
(meaning) which is only interpretable by humans,
(i.e. free text).
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B.3.4 Certificate Identifier from the Signer
The definition of the ETSI electronic signature includes: "a commitment
has been explicitly endorsed under a signature policy, at a given time,
by a signer under an identifier, e.g. a name or a pseudonym, and
optionally a role."
In many real life environments users will be able to get from different
CAs or even from the same CA, different certificates containing the
same public key for different names. The prime advantage is that a user
can use the same private key for different purposes. Multiple use of
the private key is an advantage when a smart card is used to protect
the private key, since the storage of a smart card is always limited.
When several CAs are involved, each different certificate may contain a
different identity, e.g. as a national or as an employee from a
company. Thus when a private key is used for various purposes, the
certificate is needed to clarify the context in which the private key
was used when generating the signature. Where there is the possibility
of multiple use of private keys it is necessary for the
signer to indicate to the verifier the precise certificate to be used.
Many current schemes simply add the certificate after the signed data
and thus are subject to various substitution attacks. An example of a
substitution attack is a "bad" CA that would issue a certificate to
someone with the public key of someone else. If the certificate from
the signer was simply appended to the signature and thus not protected
by the signature, any one could substitute one certificate by another
and the message would appear to be signed by some one else.
In order to counter this kind of attack, the identifier of the signer
has to be protected by the digital signature from the signer.
Although it does not provide the same advantages as the previous
technique, another technique to counter that threat has been
identified. It requires all CAs to perform a Proof Of Possession of the
private key at the time of registration. The problem with that
technique is that it does not provide any guarantee at the time of
verification and only some proof "after the event" may be obtained, if
and only if the CA keeps the Proof Of Possession in audit trail.
In order to identify unambiguously the certificate to be used for the
verification of the signature an identifier of the certificate from the
signer must be part of the signed data.
B.3.5 Role Attributes
The definition of electronic signature includes: "a commitment has been
explicitly endorsed under a non repudiation security policy, at a given
time, by a signer under an identifier, e.g. a name or a pseudonym, and
optionally a role. "
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While the name of the signer is important, the position of the signer
within a company or an organization can be even more important. Some
contracts may only be valid if signed by a user in a particular role,
e.g. a Sales Director. In many cases whom the sales Director really is,
is not that important but being sure that the signer is empowered by
his company to be the Sales Director is fundamental.
This document defines two different ways for providing this feature:
* by placing a claimed role name in the CMS signed
attributes field;
* by placing a attribute certificate containing a certified
role name in the CMS signed attributes field.
NOTE: Another possible approach would have been to use additional
attributes containing the roles name(s) in the signer's certificate.
However, it was decided not to follow this approach as it breaks the
basic philosophy of the certificate being issued for one primary
purpose. Also, by using separate certificates for management of the
signer's identity certificate and management of additional roles can
simplify the management, as new identity keys need not be issued if a
use of role is to be changed.
B.3.5.1 Claimed Role
The signer may be trusted to state his own role without any certificate
to corroborate this claim. In which case the claimed role can be added
to the signature as a signed attribute.
B.3.5.2 Certified Role
Unlike public key certificates that bind an identifier to a public key,
Attribute Certificates bind the identifier of a certificate to some
attributes, like a role. An Attribute Certificate is NOT issued by a CA
but by an Attribute Authority (AA). The Attribute Authority will be
most of the time under the control of an organization or a company that
is best placed to know which attributes are relevant for which
individual. The Attribute Authority may use or point to public key
certificates issued by any CA, provided that the appropriate trust may
be placed in that CA. Attribute Certificates may have various periods
of validity. That period may be quite short, e.g. one day. While this
requires that a new Attribute Certificate is obtained every day, valid
for that day, this can be advantageous since revocation of such
certificates may not be needed. When signing, the signer will have to
specify which Attribute Certificate it selects. In order to do
so, the Attribute Certificate will have to be included in the signed
data in order to be protected by the digital signature from the signer.
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In order to identify unambiguously the attribute certificate(s) to be
used for the verification of the signature an identifier of the
attribute certificate(s) from the signer must be part of the signed
data.
B.3.6 Signer Location
In some transactions the purported location of the signer at the time
he or she applies his signature may need to be indicated. For this
reason an optional location indicator must be able to be included.
In order to provide indication of the location of the signer at the
time he or she applied his signature a location attribute may be
included in the signature.
B.3.7 Signing Time
The definition of electronic signature includes: "a commitment has been
explicitly endorsed under a signature policy, at a given time, by a
signer under an identifier, e.g. a name or a pseudonym, and optionally a
role. "
There are several ways to address this problem. The solution adopted in
this document is to sign over a time which the signer claims is the
signing time (i.e. claimed signing time) and to require a trusted time
stamp to be obtained when building a ES with Timestamp. When a verifier
accepts a signature, the two times must be within acceptable limits.
The solution that is adopted in this document offers the major
advantage that electronic signatures can be generated without any on-
line connection to a trusted time source (i.e. they may be generated
off-line).
Thus two dates and two signatures are required:
* a signing time indicated by the signer and which is part of
the data signed by the signer (i.e. part of the basic electronic
signature);
* a time indicated by a TimeStamping Authority (TSA) which is
signed over the digital signature value of the basic electronic
signature. The signer, verifier or both may obtain the TSA
timestamp.
In order for an electronic signature to be valid under a signature
policy, it must be timestamped by a TSA where the signing time as
indicated by the signer and the time of time stamping as indicated by a
TSA must be "close enough" to meet the requirements of the signature
validation policy.
"Close enough" means a few minutes, hours or even days according to the
"Signature Validation Policy".
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NOTE: The need for Timestamping is further explained in clause B.4.5.
A further optional attribute is defined in this document to timestamp
the content, to provide proof of the existence of the content, at the
time indicated by the timestamp.
Using this optional attribute a trusted secure time may be obtained
before the document is signed and included under the digital signature.
This solution requires an on-line connection to a trusted timestamping
service before generating the signature and may not represent the
precise signing time, since it can be obtained in advance. However,
this optional attribute may be used by the signer to prove that the
signed object existed before the date included in the timestamp (see
4.12.3, Content Timestamp).
Also, the signing time should be between the time indicated by this
timestamp and time indicated by the ES-T timestamp.
B.4 Components of Validation Data
B.4.1 Revocation Status Information
A verifier will have to prove that the certificate of the signer was
valid at the time of the signature. This can be done by either:
* using Certificate Revocation Lists (CRLs);
* using responses from an on-line certificate status server
(for example; obtained through the OCSP protocol).
B.4.2 CRL Information
When using CRLs to get revocation information, a verifier will have to
make sure that he or she gets at the time of the first verification the
appropriate certificate revocation information from the signer's CA.
This should be done as soon as possible to minimize the time delay
between the generation and verification of the signature. This involves
checking that the signer certificate serial number is not included in
the CRL. The signer, the verifier or any other third party may obtain
either this CRL. If obtained by the signer, then it must be conveyed
to the verifier. It may be convenient to archive the CRL for ease of
subsequent verification or arbitration.
Alternatively, provided the CRL is archived elsewhere which is
accessible for the purpose of arbitration, then the serial number of
the CRL used may be archived together with the verified electronic
signature.
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It may happen that the certificate serial number appears in the CRL but
with the status "suspended" (i.e. on hold). In such a case, the
electronic signature is not yet valid, since it is not possible to know
whether the certificate will or will not be revoked at the end of the
suspension period. If a decision has to be taken immediately then the
signature has to be considered as invalid. If a decision can wait until
the end of the suspension period, then two cases are possible:
* the certificate serial number has disappeared from the list
and thus the certificate can be considered as valid and that CRL
must be captured and archived either by the verifier or
elsewhere and be kept accessible for the purpose of arbitration.
* the certificate serial number has been maintained on the list
with the status definitively revoked and thus the electronic
signature must be considered as invalid and discarded.
At this point the verifier may be convinced that he or she got a valid
signature, but is not yet in a position to prove at a later time that
the signature was verified as valid. Before addressing this point, an
alternative to CRL is to use OCSP responses.
B.4.3 OCSP Information
When using OCSP to get revocation information , a verifier will have to
make sure that he or she gets at the time of the first verification an
OCSP response that contains the status "valid". This should be done as
soon as possible after the generation of the signature. The signer, the
verifier or any other third party may fetch this OCSP response. Since
OSCP responses are transient and thus are not archived by any TSP
including CA, it is the responsibility of every verifier to make sure
that it is stored in a safe place. The simplest way is to store them
associated with the electronic signature. An alternative would be to
store them in some storage so that they can then be easily retrieved.
In the same way as for the case of the CRL, it may happen that the
certificate is declared as invalid but with the secondary status
"suspended".
In such a case, the electronic signature is not yet valid, since it is
not possible to know whether the certificate will or will not be
revoked at the end of the suspension period. If a decision has to be
taken immediately then the electronic signature has to be considered as
invalid. If a decision can wait until the end of the suspension period,
then two cases are possible:
* An OCSP response with a valid status is obtained at a later date
and thus the certificate can be considered as valid and that
OCSP response must be captured.
* An OCSP response with an invalid status is obtained with a
secondary status indicating that the certificate is definitively
revoked and thus the electronic signature must be considered as
invalid and discarded.
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As in the CRL case, at this point, the verifier may be convinced that
he or she got a valid signature, but is not yet in a position to prove
at a later time that the signature was verified as valid.
B.4.4 Certification Path
A verifier will have to prove that the certification path was valid, at
the time of the signature, up to a trust point according to the naming
constraints and the certificate policy constraints from the "Signature
Validation Policy". It will be necessary to capture all the
certificates from the certification path, starting with those from the
signer and ending up with those of the self-signed certificate from one
trusted root of the "Signature Validation Policy". In addition, it will
be necessary to capture the Authority Revocation Lists (ARLs) to prove
than none of the CAs from the chain was revoked at the time of the
signature.
As in the OCSP case, at this point, the verifier may be convinced that
he or she got a valid signature, but is not yet in a position to prove
at a later time that the signature was verified as valid.
B.4.5 Timestamping for Long Life of Signature
An important property for long standing signatures is that a signature,
having been found once to be valid, must continue to be so months or
years later.
A signer, verifier or both may be required to provide on request, proof
that a digital signature was created or verified during the validity
period of the all the certificates that make up the certificate path.
In this case, the signer, verifier or both will also be required to
provide proof that all the user and CA certificates used were not
revoked when the signature was created or verified.
It would be quite unacceptable, to consider a signature as invalid even
if the keys or certificates were later compromised. Thus there is a
need to be able to demonstrate that the signature keys was valid around
the time that the signature was created to provide long term evidence
of the validity of a signature.
It could be the case that a certificate was valid at the time of the
signature but revoked some time later. In this event, evidence must be
provided that the document was signed before the signing key was
revoked.
Timestamping by a Time Stamping Authority (TSA) can provide such
evidence. A time stamp is obtained by sending the hash value of the
given data to the TSA. The returned "timestamp" is a signed document
that contains the hash value, the identity of the TSA, and the time of
stamping. This proves that the given data existed before the time of
stamping. Timestamping a digital signature (by sending a hash of the
signature to the TSA) before the revocation of the signer's private
key, provides evidence that the signature has been created before the
key was revoked.
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If a recipient wants to hold a valid electronic signature he will have
to ensure that he has obtained a valid time stamp for it, before that
key (and any key involved in the validation) is revoked. The sooner the
timestamp is obtained after the signing time, the better.
It is important to note that signatures may be generated "off-line" and
time-stamped at a later time by anyone, for example by the signer or
any recipient interested in the value of the signature. The time stamp
can thus be provided by the signer together with the signed document,
or obtained by the recipient following receipt of the signed document.
The time stamp is NOT a component of the Electronic Signature, but the
essential component of the ES with Timestamp.
It is required in this document that signer's digital signature value
is timestamped by a trusted source, known as a TimeStamping Authority.
This document requires that the signer's digital signature value is
timestamped by a trusted source before the electronic signature can
become a ES with Complete validation data (ES-C). The acceptable TSAs
are specified in the Signature Validation Policy.
Should both the signer and verifier be required to timestamp the
signature value to meet the requirements of the signature policy, the
signature policy MAY specify a permitted time delay between the two
time stamps.
B.4.6 Timestamping for Long Life of Signature before CA Key Compromises
Timestamped extended electronic signatures are needed when there is a
requirement to safeguard against the possibility of a CA key in the
certificate chain ever being compromised. A verifier may be required to
provide on request, proof that the certification path and the
revocation information used a the time of the signature were valid,
even in the case where one of the issuing keys or OCSP responder keys
is later compromised.
The current document defines two ways of using timestamps to protect
against this compromise:
* Timestamp the ES with Complete validation data, when an OCSP
response is used to get the status of the certificate from the
signer.
* Timestamp only the certification path and revocation information
references when a CRL is used to get the status of the
certificate from the signer.
NOTE: the signer, verifier or both may obtain the timestamp.
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B.4.6.1 Timestamping the ES with Complete validation data
When an OCSP response is used, it is necessary to time stamp in
particular that response in the case the key from the responder would
be compromised. Since the information contained in the OCSP response is
user specific and time specific, an individual time stamp is needed for
every signature received. Instead of placing the time stamp only over
the certification path references and the revocation information
references, which include the OCSP response, the time stamp is placed
on the ES-C. Since the certification path and revocation information
references are included in the ES with Complete validation data they
are also protected. For the same cryptographic price, this provides an
integrity mechanism over the ES with Complete validation data. Any
modification can be immediately detected. It should be noticed that
other means of protecting/detecting the integrity of the ES with
Complete Validation Data exist and could be used.
Although the technique requires a time stamp for every signature, it is
well suited for individual users wishing to have an integrity protected
copy of all the validated signatures they have received.
By timestamping the complete electronic signature, including the
digital signature as well as the references to the certificates and
revocation status information used to support validation of that
signature, the timestamp ensures that there is no ambiguity in the
means of validating that signature.
This technique is referred to as ES with eXtended validation data (ES-
X), type 1 Timestamped in this document.
NOTE: Trust is achieved in the references by including a hash of the
data being referenced.
If it is desired for any reason to keep a copy of the additional data
being referenced, the additional data may be attached to the electronic
signature, in which case the electronic signature becomes a ES-X Long
as defined by this document.
A ES-X Long Timestamped is simply the concatenation of a ES-X
Timestamped with a copy of the additional data being referenced.
B.4.6.2 Timestamping Certificates and Revocation Information
References Timestamping each ES with Complete validation data as
defined above may not be efficient, particularly when the same set of
CA certificates and CRL information is used to validate many
signatures.
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Timestamping CA certificates will stop any attacker from issuing bogus
CA certificates that could be claimed to existing before the CA key was
compromised. Any bogus timestamped CA certificates will show that the
certificate was created after the legitimate CA key was compromised. In
the same way, timestamping CA CRLs, will stop any attacker from issuing
bogus CA CRLs which could be claimed to existing before the CA key was
compromised.
Timestamping of commonly used certificates and CRLs can be done
centrally, e.g. inside a company or by a service provider. This method
reduces the amount of data the verifier has to timestamp, for example
it could reduce to just one time stamp per day (i.e. in the case were
all the signers use the same CA and the CRL applies for the whole day).
The information that needs to be time stamped is not the actual
certificates and CRLs but the unambiguous references to those
certificates and CRLs.
To comply with extended validation data, type 2 Timestamped, this
document requires the following:
* All the CA certificates references and revocation information
references (i.e. CRLs) used in validating the ES-C are covered
by one or more timestamp.
Thus a ES-C with a timestamp signature value at time T1, can be proved
valid if all the CA and CRL references are timestamped at time T1+.
B.4.7 Timestamping for Long Life of Signature
Advances in computing increase the probability of being able to break
algorithms and compromise keys. There is therefore a requirement to be
able to protect electronic signatures against this probability.
Over a period of time weaknesses may occur in the cryptographic
algorithms used to create an electronic signature (e.g. due to the time
available for cryptoanalysis, or improvements in cryptoanalytical
techniques). Before this such weaknesses become likely, a verifier
should take extra measures to maintain the validity of the electronic
signature. Several techniques could be used to achieve this goal
depending on the nature of the weakened cryptography. In order to
simplify, a single technique, called Archive validation data, covering
all the cases is being used in this document.
Archive validation data consists of the Complete validation data and
the complete certificate and revocation data, time stamped together
with the electronic signature. The Archive validation data is
necessary if the hash function and the crypto algorithms that were used
to create the signature are no longer secure. Also, if it cannot be
assumed that the hash function used by the Time Stamping Authority is
secure, then nested timestamps of Archived Electronic Signature are
required.
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The potential for Trusted Service Provider (TSP) key compromise should
be significantly lower than user keys, because TSP(s) are expected to
use stronger cryptography and better key protection. It can be expected
that new algorithms (or old ones with greater key lengths) will be
used. In such a case, a sequence of timestamps will protect against
forgery. Each timestamp needs to be affixed before either the
compromise of the signing key or of the cracking of the algorithms used
by the TSA. TSAs (TimeStamping Authorities) should have long keys (e.g.
which at the time of drafting this document was 2048 bits for the
signing RSA algorithm) and/or a "good" or different algorithm.
Nested timestamps will also protect the verifier against key compromise
or cracking the algorithm on the old electronic signatures.
The process will need to be performed and iterated before the
cryptographic algorithms used for generating the previous time stamp
are no longer secure. Archive validation data may thus bear multiple
embedded time stamps.
B.4.8 Reference to Additional Data
Using type 1 or 2 of Timestamped extended validation data verifiers
still needs to keep track of all the components that were used to
validate the signature, in order to be able to retrieve them again
later on. These components may be archived by an external source like a
trusted service provider, in which case referenced information that is
provided as part of the ES with Complete validation data (ES-C) is
adequate. The actual certificates and CRL information reference in the
ES-C can be gathered when needed for arbitration.
B.4.9 Timestamping for Mutual Recognition
In some business scenarios both the signer and the verifier need to
timestamp their own copy of the signature value. Ideally the two
timestamps should be as close as possible to each other.
Example: A contract is signed by two parties A and B representing their
respective organizations, to timestamp the signer and verifier data two
approaches are possible:
* under the terms of the contract pre-defined common "trusted"
TSA may be used;
* if both organizations run their own timestamping services, A
and B can have the transaction timestamped by these two
timestamping services.In the latter case, the electronic
signature will only be considered as valid, if both timestamps
were obtained in due time (i.e. there should not be a long
delay between obtaining the two timestamps). Thus, neither A
nor B can repudiate the signing time indicated by their own
timestamping service.
Therefore, A and B do not need to agree on a common "trusted" TSA to
get a valid transaction.
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It is important to note that signatures may be generated "off-line" and
timestamped at a later time by anyone, e.g. by the signer or any
recipient interested in validating the signature. The timestamp over
the signature from the signer can thus be provided by the signer
together with the signed document, and /or obtained by the verifier
following receipt of the signed document.
The business scenarios may thus dictate that one or more of the long-
term signature timestamping methods describe above be used. This will
need to be part of a mutually agreed the Signature Validation Policy
with is part of the overall signature policy under which digital
signature may be used to support the business relationship between the
two parties.
B.4.10 TSA Key Compromise
TSA servers should be built in such a way that once the private
signature key is installed, that there is minimal likelihood of
compromise over as long as possible period. Thus the validity period
for the TSA's keys should be as long as possible.
Both the ES-T and the ES-C contain at least one time stamp over the
signer's signature. In order to protect against the compromise of the
private signature key used to produce that timestamp, the Archive
validation data can be used when a different TimeStamping Authority key
is involved to produce the additional timestamp. If it is believed that
the TSA key used in providing an earlier timestamp may ever be
compromised (e.g. outside its validity period), then the ES-A should be
used. For extremely long periods this may be applied repeatedly using
new TSA keys.
B.5 Multiple Signatures
Some electronic signatures may only be valid if they bear more than one
signature. This is the case generally when a contract is signed between
two parties. The ordering of the signatures may or may not be
important, i.e. one may or may not need to be applied before the other.
Several forms of multiple and counter signatures need to be supported,
which fall into two basic categories:
* independent signatures;
* embedded signatures.
Independent signatures are parallel signatures where the ordering of
the signatures is not important. The capability to have more than one
independent signature over the same data must be provided.
Embedded signatures are applied one after the other and are used where
the order the signatures are applied is important. The capability to
sign over signed data must be provided.
These forms are described in clause 4.13. All other multiple signature
schemes, e.g. a signed document with a countersignature, double
countersignatures or multiple signatures, can be reduced to one or more
occurrence of the above two cases.
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Annex C (informative):
C.1 Signature Policy and Signature Validation Policy
The definition of electronic signature mentions: "a commitment has been
explicitly endorsed under a "Signature Policy", at a given time, by a
signer under an identifier, e.g. a name or a pseudonym, and optionally
a role. "
Electronic signatures are commonly applied within the context of a
legal or contractual framework. This establishes the requirements on
the electronic signatures and any special semantics (e.g. agreement,
intent). These requirements may be defined in very general abstract
terms or in terms of detailed rules. The specific semantics associated
with an electronic signature implied by a legal or contractual
framework are outside the scope of this document.
If the signature policy is recognized, within the legal/contractual
context, as providing commitment, then the signer explicitly agrees
with terms and conditions which are implicitly or explicitly part of
the signed data.
When two independent parties want to evaluate an electronic signature,
it is fundamental that they get the same result. It is therefore
important that the conditions agreed by the signer at the time of
signing are indicated to the verifier and any arbitrator. An aspect
that enables this to be known by all parties is the signature policy.
The technical implications of the signature policy on the electronic
signature with all the validation data are called the "Signature
Validation Policy". The signature validation policy specifies
the rules used to validate the signature.
This document does not mandate the form and encoding of the
specification of the signature policy. However, for a given signature
policy there must be one definitive form that has a unique binary
encoded value.
This document includes, as an option, a formal structure for signature
validation policy based on the use of Abstract Syntax Notation 1
(ASN.1).
Given the specification of the signature policy and its hash value an
implementation of a verification process must obey the rules defined
in the specification.
This document places no restriction on how it should be implemented.
Provide the implementation conforms to the conformance requirements as
define in clause 14.1, 14.2 and 14.3 implementation options include:
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A validation process that supports a specific signature policy as
identified by the signature policy OID. Such an implementation should
conform to a human readable description provided all the processing
rules of the signature policy are clearly defined. However, if
additional policies need to be supported, then such an implementation
would need to be customized for each additional policy. This type of
implementation may be simpler to implement initially, but can be
difficult to enhance to support numerous additional signature policies.
A validation process that is dynamically programmable and able to adapt
its validation rules in accordance with a description of the signature
policy provided in a computer-processable language. This present
document defines such a policy using an ASN.1 structure (see 6.1). This
type of implementation could support multiple signature policies
without being modified every time, provided all the validation rules
specified as part of the signature policy are known by the
implementation. (i.e. only requires modification if there are
additional rules specified).
The precise content of a signature policy is not mandated by the
current document. However, a signature policy must be sufficiently
definitive to avoid any ambiguity as to its implementation
requirements. It must be absolutely clear under which conditions an
electronic signature should be accepted. For this reason, it should
contain the following information:
* General information about the signature policy which includes:
- a unique identifier of the policy;
- the name of the issuer of the policy;
- the date the policy was issued;
- the field of application of the policy.
* The signature verification policy which includes:
- the signing period,
- a list of recognized commitment types;
- rules for Use of Certification Authorities;
- rules for Use of Revocation Status Information;
- rules for Use of Roles;
- rules for use of Timestamping and Timing;
- signature verification data to be provided by the
signer/collected by verifier;
- any constraints on signature algorithms and key lengths.
* Other signature policy rules required to meet the objectives of
the signature.
Variations of the validation policy rules may apply to different
commitment types.
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C.2 Identification of Signature Policy
When data is signed the signer indicates the signature policy
applicable to that electronic signature by including an object
identifier for the signature policy with the signature. The signer and
verifier must apply the rules specified by the identified policy. In
addition to the identifier of the signature policy the signer must
include the hash of the signature policy, so it can be verified that
the policy selected by the signer is the identical to the one being
used the verifier.
A signature policy may be qualified by additional information. This can
includes:
* A URL where a copy of the Signature Policy may be obtained;
* A user notice that should be displayed when the signature is
verified;
If no signature policy is identified then the signature may be assumed
to have been generated/verified without any policy constraints, and
hence may be given no specific legal or contractual significance
through the context of a signature policy.
A "Signature Policy" will be identifiable by an OID (Object Identifier)
and verifiable using a hash of the signature policy.
C.3 General Signature Policy Information
General information should be recorded about the signature policy along
with the definition of the rules which form the signature policy as
described in subsequent subclauses. This should include:
* Policy Object Identifier: The "Signature Policy" will be
identifiable by an OID (Object Identifier) whose last component
(i.e. right most) is an integer that is specific to a particular
version issued on the given date.
* Date of issue: When the "Signature Policy" was issued.
* Signature Policy Issuer name: An identifier for the body
responsible for issuing the Signature Policy. This may be used
by the signer or verifying in deciding if a policy is to be
trusted, in which case the signer/verifier must authenticate
the origin of the signature policy as coming from the identified
issuer.
* Signing period: The start time and date, optionally with an end
time and date, for the period over which the signature policy
may be used to generate electronic signatures.
* Field of application: This defines in general terms the general
legal/contract/application contexts in which the signature
policy is to be used and the specific purposes for which the
electronic signature is to be applied.
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C.4 Recognized Commitment Types
The signature validation policy may recognize one or more types of
commitment as being supported by electronic signatures produced under
the security policy.If an electronic signature does not contain a
recognized commitment type then the semantics of the electronic
signature is dependent on the data being signed and the context in
which it is being used.
Only recognized commitment types are allowed in an electronic
signature.
The definition of a commitment type includes:
* the object identifier for the commitment;
* the contractual/legal/application context in which the signature
may be used (e.g. submission of messages);
* a description of the support provided within the terms of the
context (e.g. proof that the identified source submitted the
message if the signature is created when message submission is
initiated).
The definition of a commitment type can be registered:
* as part of the validation policy;
* as part of the application/contract/legal environment;
* as part of generic register of definitions.
The legal/contractual context will determine the rules applied to the
signature, as defined by the signature policy and its recognized
commitment types, make it fit for purpose intended.
C.5 Rules for Use of Certification Authorities
The certificate validation process of the verifier, and hence the
certificates that may be used by the signer for a valid electronic
signature, may be constrained by the combination of the trust point and
certificate path constraints in the signature validation policy.
C.5.1 Trust Points
The signature validation policy defines the certification authority
trust points that are to be used for signature verification. Several
trust points may be specified under one signature policy. Specific
trust points may be specified for a particular type of commitment
defined under the signature policy. For a signature to be valid a
certification path must exists between the Certification Authority
that has granted the certificate selected by the signer (i.e. the used
user-certificate) and one of the trust point of the "Signature
Validation Policy".
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C.5.2 Certification Path
There may be constraints on the use of certificates issued by one or
more CA(s) in the certificate chain and trust points. The two prime
constraints are certificate policy constraints and naming constraints:
* Certificate policy constraints limit the certification chain
between the user certificate and the certificate of the trusted
point to a given set of certificate policies, or equivalents
identified through certificate policy mapping.
* The naming constraints limit the forms of names that the CA is
allowed to certify.
Name constraints are particularly important when a "Signature policy"
identifies more than one trust point. In this case, a certificate of a
particular trusted point may only be used to verify signatures from
users with names permitted under the name constraint.
Certificate Authorities may be organized in a tree structure, this tree
structure may represent the trust relationship between various CA(s)
and the users CA. Alternatively, a mesh relationship may exist where a
combination of tree and peer cross-certificates may be used. The
requirement of the certificate path in this document is that it
provides the trust relationship between all the CAs and the signers
user certificate. The starting point from a verification point of view,
is the "trust point". A trust point is usually a CA that publishes
self-certified certificates, is the starting point from which the
verifier verifies the certificate chain. Naming constraints may
apply from the trust point, in which case they apply throughout the set
of certificates that make up the certificate path down to the signer's
user certificate.
Policy constraints can be easier to process but to be effective require
the presence of a certificate policy identifier in the certificates
used in a certification path.
Certificate path processing, thus generally starts with one of the
trust point from the signature policy and ends with the user
certificate. The certificate path processing procedures defined in RFC
2459 clause 6 identifies the following initial parameters that are
selected by the verifier in certificate path processing:
* acceptable certificate policies;
* naming constraints in terms of constrained and excluded naming
subtree;
* requirements for explicit certificate policy indication and
whether certificate policy mapping are allowed;
* restrictions on the certificate path length.
The signature validation policy identifies constraints on these
parameters.
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C.5 Revocation Rules
The signature policy should defines rules specifying requirements for
the use of certificate revocation lists (CRLs) and/or on-line
certificate status check service to check the validity of a certificate.
These rules specify the mandated minimum checks that must be carried
out.
It is expected that in many cases either check may be selected with
CRLs checks being carried out for certificate status that are
unavailable from OCSP servers. The verifier may take into account
information in the certificate in deciding how best to check the
revocation status (e.g. a certificate extension field about authority
information access or a CRL distribution point) provided that it does
not conflict with the signature policy revocation rules.
C.6 Rules for the Use of Roles
Roles can be supported as claimed roles or as certified roles using
Attribute Certificates.
C.6.1 Attribute Values
When signature under a role is mandated by the signature policy, then
either Attribute Certificates may be used or the signer may provide a
claimed role attribute. The acceptable attribute types or values may be
dependent on the type of commitment. For example, a user may have
several roles that allow the user to sign data that imply commitments
based on one or more of his roles.
C.6.2 Trust Points for Certified Attributes
When a signature under a certified role is mandated by the signature
policy, Attribute Authorities are used and need to be validated as part
of the overall validation of the electronic signature. The trust points
for Attribute Authorities do not need to be the same as the trust
points to evaluate a certificate from the CA of the signer. Thus the
trust point for verifying roles need not be the same as trust point
used to validate the certificate path of the user's key.
Naming and certification policy constraints may apply to the AA in
similar circumstance to when they apply to CA. Constraints on the AA
and CA need not be exactly the same.
AA(s) may be used when a signer is creating a signature on behalf of an
organization, they can be particularly useful when the signature
represents an organizational role. AA(s) may or may not be the same
authority as CA(s).
Thus, the Signature Policy identifies trust points that can be used for
Attribute Authorities, either by reference to the same trust points as
used for Certification Authorities, or by an independent list.
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C.6.3 Certification Path for Certified Attributes
Attribute Authorities may be organized in a tree structure in similar
way to CA where the AAs are the leafs of such a tree. Naming and other
constraints may be required on attribute certificate paths in a similar
manner to other electronic signature certificate paths.
Thus, the Signature Policy identify constraints on the following
parameters used as input to the certificate path processing:
* acceptable certificate policies, including requirements for
explicit certificate policy indication and whether certificate
policy mapping is allowed;
* naming constraints in terms of constrained and excluded naming
subtrees;
* restrictions on the certificate path length.
C.7 Rules for the Use of Timestamping and Timing
The following rules should be used when specifying, constraints on the
certificate paths for timestamping authorities, constraints on the
timestamping authority names and general timing constraints.
C.7.1 Trust Points and Certificate Paths
Signature keys from timestamping authorities will need to be supported
by a certification path. The certification path used for timestamping
authorities requires a trustpoint and possibly path constraints in the
same way that the certificate path for the signer's key.
C.7.2 Timestamping Authority Names
Restrictions may need to be placed by the validation policy on the
named entities that may act a timestamping authorities.
C.7.3 Timing Constraints - Caution Period
Before an electronic signature may really be valid, the verifier has to
be sure that the holder of the private key was really the only one in
possession of key at the time of signing. However, there is an
inevitable delay between a compromise or loss of key being noted, and a
report of revocation being distributed. To allow greater confidence in
the validity of a signature, a "cautionary period" may be identified
before a signature may be said to be valid with high confidence. A
verifier may revalidate a signature after this cautionary signature, or
wait for this period before validating a signature.
The validation policy may specify such a cautionary period.
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C.7.4 Timing Constraints - Timestamp Delay
There will be some delay between the time that a signature is created
and the time the signer's digital signature is timestamped. However,
the longer this elapsed period the greater the risk of the signature
being invalidated due to compromise or deliberate revocation of its
private signing key by the signer. Thus the signature policy should
specify a maximum acceptable delay between the signing time as claimed
by the signer and the time included within the timestamp.
C.8 Rules for Verification Data to be followed
By specifying the requirements on the signer and verifier the
responsibilities of the two parties can be clearly defined to establish
all the necessary information.
These verification data rules should include:
* requirements on the signer to provide given signed attributes;
* requirements on the verifier to obtain additional certificates, CRLs,
results of on line certificate status checks and to use timestamps (if
no already provided by the signer).
C.9 Rules for Algorithm Constraints and Key Lengths
The signature validation policy may identify a set of signing
algorithms (hashing, public key, combinations) and minimum key lengths
that may be used:
* by the signer in creating the signature;
* in end entity public key Certificates;
* CA Certificates;
* attribute Certificates;
* by the timestamping authority.
C.10 Other Signature Policy Rules
The signature policy may specify additional policy rules, for example
rules that relate to the environment used by the signer. These
additional rules may be defined in computer processable and/or human
readable form.
C.11 Signature Policy Protection
When signer or verifier obtains a copy of the Signature Policy from an
issuer, the source should be authenticated (for example by using
electronic signatures). When the signer references a signature policy
the Object Identifier (OID) of the policy, the hash value and the hash
algorithm OID of that policy must be included in the Electronic
Signature.
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It is a mandatory requirement of this present document that the
signature policy value computes to one, and only one hash value using
the specified hash algorithm. This means that there must be a single
binary value of the encoded form of the signature policy for the unique
hash value to be calculated. For example, there may exist a particular
file type, length and format on which the hash value is calculated
which is fixed and definitive for a particular signature policy.
The hash value may be obtained by:
the signer performing his own computation of the hash over the
signature policy using his preferred hash algorithm permitted by
the signature policy, and the definitive binary encoded form.
the signer, having verified the source of the policy, may use
both the hash algorithm and the hash value included in the
computer processable form of the policy (see section 6.1).
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Annex D (informative):
Identifiers and roles
D.1 Signer Name Forms
The name used by the signer, held as the subject in the signer's
certificate, must uniquely identify the entity. The name must be
allocated and verified on registration with the Certification
Authority, either directly or indirectly through a Registration
Authority, before being issued with a Certificate.
This document places no restrictions on the form of the name. The
subject's name may be a distinguished name, as defined in ITU-T
Recommendation X.500 [15], held in the subject field of the
certificate, or any other name form held in the X.509 subjectAltName
certificate extension field. In the case that the subject has no
distinguished name, the subject name can be an empty
sequence and the subjectAltName extension must be critical.
D.2 TSP Name Forms
All TSP name forms (Certification Authorities, Attribute Authorities
and TimeStamping Authorities) must be in the form of a distinguished
name held in the subject field of the certificate.
The TSP name form must include identifiers for the organization
providing the service and the legal jurisdiction (e.g. country) under
which it operates.
D.3 Roles and Signer Attributes
Where a signer signs as an individual but wishes to also identify
him/herself as acting on behalf of an organization, it may be necessary
to provide two independent forms of identification. The first identity,
with is directly associated with the signing key identifies him/her as
an individual. The second, which is managed independently, identifies
that person acting as part of the organization, possibly with a given
role.
In this case the first identity is carried in the
subject/subjectAltName field of the signer's certificate as described
above.
This document supports the following means of providing a second form
of identification:
* by placing a secondary name field containing a claimed role in
the CMS signed attributes field;
* by placing an attribute certificate containing a certified role
in the CMS signed attributes field.
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