RFC 3126
Electronic Signature Formats for long term electronic signatures
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-ElectronicSignatureFormats-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) } -- 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 Work in Progress
TimeStampToken
FROM PKIXTSP
{iso(1) identified-organization(3) dod(6) internet(1)
security(5) mechanisms(5) pkix(7) id-mod(0) id-mod-tsp(13)}
-- 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) }
-- 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 }
"SignaturePolicy CHOICE {
SignaturePolicyId SignaturePolicyId,
SignaturePolicyImplied SignaturePolicyImplied
}
SignaturePolicyId ::= SEQUENCE {
sigPolicyIdentifier SigPolicyId,
sigPolicyHash SigPolicyHash,
sigPolicyQualifiers SEQUENCE SIZE (1..MAX) OF
SigPolicyQualifierInfo OPTIONAL
}
SignaturePolicyImplied ::= NULL
SigPolicyId ::= OBJECT IDENTIFIER
SigPolicyHash ::= OtherHashAlgAndValue
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))
}
-- 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}
-- 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 Time-Stamp
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 Time-Stamp
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
-- 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 OTHERCertID
-- 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 OtherHash,
crlIdentifier CrlIdentifier OPTIONAL
}
CrlIdentifier ::= SEQUENCE {
crlissuer Name,
crlIssuedTime UTCTime,
crlNumber INTEGER OPTIONAL
}
OcspListID ::= SEQUENCE {
ocspResponses SEQUENCE OF OcspResponsesID}
OcspResponsesID ::= SEQUENCE {
ocspIdentifier OcspIdentifier,
ocspRepHash OtherHash OPTIONAL
}
OcspIdentifier ::= SEQUENCE {
ocspResponderID ResponderID,
-- as in OCSP response data
producedAt GeneralizedTime
-- as in OCSP response data
}
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 Time-Stamp
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
-- Archive Time-Stamp
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
END -- ETS-ElectronicSignatureFormats-88syntax --
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-ElectronicSignatureFormats-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
-- Cryptographic 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}
-- OCSP 2560
BasicOCSPResponse, ResponderID
FROM OCSP
-- { OID not assigned }
-- Time Stamp Protocol Work in Progress TimeStampToken
FROM PKIXTSP
{iso(1) identified-organization(3) dod(6) internet(1)
security(5) mechanisms(5) pkix(7) id-mod(0) id-mod-tsp(13)}
-- 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) }
-- 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 }
"SignaturePolicy CHOICE {
SignaturePolicyId SignaturePolicyId,
SignaturePolicyImplied SignaturePolicyImplied
}
SignaturePolicyId ::= SEQUENCE {
sigPolicyIdentifier SigPolicyId,
sigPolicyHash SigPolicyHash,
sigPolicyQualifiers SEQUENCE SIZE (1..MAX) OF
SigPolicyQualifierInfo OPTIONAL
}
SignaturePolicyImplied ::= NULL
SigPolicyId ::= OBJECT IDENTIFIER
SigPolicyHash ::= OtherHashAlgAndValue
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))
}
-- 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}
-- 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 Time-Stamp
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 Time-Stamp
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
-- 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 OTHERCertID
-- 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 OtherHash,
crlIdentifier CrlIdentifier OPTIONAL}
CrlIdentifier ::= SEQUENCE {
crlissuer Name,
crlIssuedTime UTCTime,
crlNumber INTEGER OPTIONAL
}
OcspListID ::= SEQUENCE {
ocspResponses SEQUENCE OF OcspResponsesID}
OcspResponsesID ::= SEQUENCE {
ocspIdentifier OcspIdentifier,
ocspRepHash OtherHash OPTIONAL
}
OcspIdentifier ::= SEQUENCE {
ocspResponderID ResponderID,
-- As in OCSP response data
producedAt GeneralizedTime
-- As in OCSP response data
}
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 Time-Stamp
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
-- Archive Time-Stamp
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
END -- ETS-ElectronicSignatureFormats-97Syntax
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.
The signature policy may be explicitly identified or may be implied
by the semantics of the data being signed and other external data
like a contract being referenced which itself refers to a signature
policy.
An explicit 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:
* Information about the signature policy that can be displayed to
the signer or the verifiers.
* 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.
An explicit Signature Validation Policy may be structured so that it
can be computer processable. Any format of the signature validation
policy is allowed by this document. However, for a given explicit
signature policy there must be one definitive form that has a unique
binary encoded value.
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 same signature policy must be used by the signer and verifier. The signature policy may be explicitly identified or may be implied by the semantics of the data being signed and other external data which designate the signature policy to be used. By signing over the signature policy identifier the signer explicitly indicates that he or she has applied the signature policy in creating the signature. Thus, undertakes any explicit or implied commitments. In order to unambiguously identify an explicit signature policy that is to be used to verify the signature an identifier and hash of the "Signature policy" shall be part of the signed data. Additional information about the explicit policy (e.g., web reference to the document) may be carried as "qualifiers" to the signature policy identifier. When the signature policy not explicitly identified, but is implied by the semantics of the data being signed, then the signature will include a signature policy identifier that indicates that the signature policy is implied. In this case the verification rules must be determined by using other external data which will designate the signature policy to be used. If it may be determined from the context that all the documents to be verified refer to the same signature policy, then that policy may be predetermined or fixed within the application. 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).B.3.3 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.3.4 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."
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.3.4.1 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.3.4.2 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, a reference to the Attribute Certificate will have to be included in the signed data in order to be protected by the digital signature from the signer. 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.3.5 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.3.6 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 Time-Stamp. 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 Time-Stamping Authority (TSA) which is signed over the digital signature value of the basic electronic signature. The signer, verifier or both may obtain the TSA time-stamp.
In order for an electronic signature to be valid under a signature policy, it must be time-stamped 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". NOTE: The need for Time-Stamping is further explained in clause B.4.5. A further optional attribute is defined in this document to time-stamp the content, to provide proof of the existence of the content, at the time indicated by the time-stamp. 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 time-stamping 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 time-stamp (see 3.12.3, Content Time-Stamp). Also, the signing time should be between the time indicated by this time-stamp and time indicated by the ES-T time-stamp.B.3.7 Content Format
When presenting signed data to a human user it may be important that there is no ambiguity as to the presentation of the signed information to the relying party. In order for the appropriate representation (text, sound or video) to be selected by the relying party a content hint may be indicated by the signer. If a relying party system does not use the format specified in the content hints to present the data to the relying party, the electronic signature may not be valid.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. 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.
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 Time-Stamping 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. Time-Stamping 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 "time-stamp" 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. Time-Stamping 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. 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 time-stamp 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 Time-Stamp. It is required in this document that signer's digital signature value is time-stamped by a trusted source, known as a Time-Stamping Authority. This document requires that the signer's digital signature value is time-stamped 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 time-stamp 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 Time-Stamping before CA Key Compromises
Time-Stamped 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 time-stamps to protect against this compromise: * Time-Stamp the ES with Complete validation data, when an OCSP response is used to get the status of the certificate from the signer. * Time-Stamp 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 time-stamp.B.4.6.1 Time-Stamping 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 time-stamping 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 time-stamp 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 Time-Stamped 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 Time-Stamped is simply the concatenation of a ES-X Time- Stamped with a copy of the additional data being referenced.B.4.6.2 Time-Stamping Certificates and Revocation Information
References Time-Stamping 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. Time-Stamping 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 time-stamped CA certificates will show that the certificate was created after the legitimate CA key was
compromised. In the same way, time-stamping CA CRLs, will stop any
attacker from issuing bogus CA CRLs which could be claimed to
existing before the CA key was compromised.
Time-Stamping 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 time-stamp, 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 Time-stamped, 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 time-stamp.
Thus a ES-C with a time-stamp signature value at time T1, can be
proved valid if all the CA and CRL references are time-stamped at
time T1+.
B.4.7 Time-Stamping 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 time-stamps of Archived Electronic Signature are required. 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 time-stamps will protect against forgery. Each time-stamp needs to be affixed before either the compromise of the signing key or of the cracking of the algorithms used by the TSA. TSAs (Time-Stamping 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 time-stamps 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 Time-Stamped 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 Time-Stamping for Mutual Recognition
In some business scenarios both the signer and the verifier need to time-stamp their own copy of the signature value. Ideally the two time-stamps 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 time-stamp 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 time-stamping services, A
and B can have the transaction time-stamped by these two time-
stamping services. In the latter case, the electronic
signature will only be considered as valid, if both time-stamps
were obtained in due time (i.e., there should not be a long
delay between obtaining the two time-stamps). Thus, neither A
nor B can repudiate the signing time indicated by their own
time-stamping service.
Therefore, A and B do not need to agree on a common "trusted" TSA to
get a valid transaction.
It is important to note that signatures may be generated "off-line"
and time-stamped at a later time by anyone, e.g., by the signer or
any recipient interested in validating the signature. The time-stamp
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 time-stamping 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 time-stamp, the
Archive validation data can be used when a different Time-Stamping
Authority key is involved to produce the additional time-stamp. If
it is believed that the TSA key used in providing an earlier time-
stamp 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 may 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 3.13. 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.
Annex C (informative): Identifiers and roles
C.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 [RFC2459],
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.
C.2 TSP Name Forms
All TSP name forms (Certification Authorities, Attribute Authorities
and Time-Stamping Authorities) must be in the form of a distinguished
name held in the subject field of the certificate.
The TSP name form must include the legal jurisdiction (i.e., country)
under which it operates and an identification for the organization
providing the service.
C.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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