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Network Working Group                                          J. SchaadRequest for Comments: 5035                       Soaring Hawk ConsultingUpdates:2634                                                August 2007Category: Standards TrackEnhanced Security Services (ESS) Update:Adding CertID Algorithm AgilityStatus of This Memo   This document specifies an Internet standards track protocol for the   Internet community, and requests discussion and suggestions for   improvements.  Please refer to the current edition of the "Internet   Official Protocol Standards" (STD 1) for the standardization state   and status of this protocol.  Distribution of this memo is unlimited.Abstract   In the original Enhanced Security Services for S/MIME document (RFC2634), a structure for cryptographically linking the certificate to   be used in validation with the signature was introduced; this   structure was hardwired to use SHA-1.  This document allows for the   structure to have algorithm agility and defines a new attribute for   this purpose.Table of Contents1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .21.1.  Notation . . . . . . . . . . . . . . . . . . . . . . . . .21.2.  Updates toRFC 2634  . . . . . . . . . . . . . . . . . . .2   2.  ReplaceSection 5.4 'Signing Certificate Attribute       Definitions' . . . . . . . . . . . . . . . . . . . . . . . . .3   3.  Insert NewSection 5.4.1 'Signing Certificate Attribute       Definition Version 2'  . . . . . . . . . . . . . . . . . . . .4   4.  Insert NewSection 5.4.1.1 'Certificate Identification       Version 2' . . . . . . . . . . . . . . . . . . . . . . . . . .5   5.  Insert NewSection 5.4.2 'Signing Certificate Attribute       Definition Version 1'  . . . . . . . . . . . . . . . . . . . .7   6.  Insert NewSection 5.4.2.1 'Certificate Identification       Version 1' . . . . . . . . . . . . . . . . . . . . . . . . . .87.  Security Considerations  . . . . . . . . . . . . . . . . . . .98.  Normative References . . . . . . . . . . . . . . . . . . . . .10Appendix A.  ASN.1 Module  . . . . . . . . . . . . . . . . . . . .11Schaad                      Standards Track                     [Page 1]

RFC 5035                    ESSCertID Update                 August 20071.  Introduction   In the original Enhanced Security Services (ESS) for S/MIME document   [ESS], a structure for cryptographically linking the certificate to   be used in validation with the signature was defined.  This   structure, called ESSCertID, identifies a certificate by its hash.   The structure is hardwired to use a SHA-1 hash value.  The recent   attacks on SHA-1 require that we define a new attribute that allows   for the use of different algorithms.  This document performs that   task.   This document defines the structure ESSCertIDv2 along with a new   attribute SigningCertificateV2, which uses the updated structure.   This document allows for the structure to have algorithm agility by   including an algorithm identifier and defines a new signed attribute   to use the new structure.   This document specifies the continued use of ESSCertID to ensure   compatibility when SHA-1 is used for certificate disambiguation.1.1.  Notation   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this   document are to be interpreted as described in [RFC2119].1.2.  Updates toRFC 2634   This document updatesSection 5.4 of RFC 2634.  Once the updates are   applied, the revised section will have the following structure:   5.4  Signing Certificate Attribute Definitions   5.4.1  Signing Certificate Attribute Definition Version 2   5.4.1.1  Certificate Identification Version 2   5.4.2  Signing Certificate Attribute Definition Version 1   5.4.2.1  Certificate Identification Version 1   In addition, the ASN.1 module inAppendix A is replaced.Schaad                      Standards Track                     [Page 2]

RFC 5035                    ESSCertID Update                 August 20072.  ReplaceSection 5.4 'Signing Certificate Attribute Definitions'   5.4 Signing Certificate Attribute Definitions   The signing certificate attribute is designed to prevent simple   substitution and re-issue attacks, and to allow for a restricted set   of certificates to be used in verifying a signature.   Two different attributes exist for this due to a flaw in the original   design.  The only substantial difference between the two attributes   is that SigningCertificateV2 allows for hash algorithm agility, while   SigningCertificate forces the use of the SHA-1 hash algorithm.  With   the recent advances in the ability to create hash collisions for   SHA-1, it is wise to move forward sooner rather than later.   When the SHA-1 hash function is used, the SigningCertificate   attribute MUST be used.  The SigningCertificateV2 attribute MUST be   used if any algorithm other than SHA-1 is used and SHOULD NOT be used   for SHA-1.  Applications SHOULD recognize both attributes as long as   they consider SHA-1 able to distinguish between two different   certificates, (i.e., the possibility of a collision is sufficiently   low).  If both attributes exist in a single message, they are   independently evaluated.   Four cases exist that need to be taken into account when using this   attribute for correct processing:   1.  Signature validates and the hashes match: This is the success       case.   2.  Signature validates and the hashes do not match: In this case,       the certificate contained the correct public key, but the       certificate containing the public key is not the one that the       signer intended to be used.  In this case the application should       attempt a search for a different certificate with the same public       key and for which the hashes match.  If no such certificate can       be found, this is a failure case.   3.  Signature fails validation and the hashes match: In this case, it       can be assumed that the signature has been modified in some       fashion.  This is a failure case.   4.  Signature fails validation and the hashes do not match: In this       case, it can be either that the signature has been modified, or       that the wrong certificate has been used.  Applications should       attempt a search for a different certificate that matches the       hash value in the attribute and use the new certificate to retry       the signature validation.Schaad                      Standards Track                     [Page 3]

RFC 5035                    ESSCertID Update                 August 20073.  Insert NewSection 5.4.1 'Signing Certificate Attribute Definition    Version 2'   5.4.1 Signing Certificate Attribute Definition Version 2   The signing certificate attribute is designed to prevent the simple   substitution and re-issue attacks, and to allow for a restricted set   of certificates to be used in verifying a signature.   SigningCertificateV2 is identified by the OID:       id-aa-signingCertificateV2 OBJECT IDENTIFIER ::= { iso(1)           member-body(2) us(840) rsadsi(113549) pkcs(1) pkcs9(9)           smime(16) id-aa(2) 47 }   The attribute has the ASN.1 definition:       SigningCertificateV2 ::=  SEQUENCE {           certs        SEQUENCE OF ESSCertIDv2,           policies     SEQUENCE OF PolicyInformation OPTIONAL       }   certs      contains the list of certificates that are to be used in      validating the message.  The first certificate identified in the      sequence of certificate identifiers MUST be the certificate used      to verify the signature.  The encoding of the ESSCertIDv2 for this      certificate SHOULD include the issuerSerial field.  If other      constraints ensure that issuerAndSerialNumber will be present in      the SignerInfo, the issuerSerial field MAY be omitted.  The      certificate identified is 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.      If more than one certificate is present, subsequent certificates      limit the set of certificates that are used during validation.      Certificates can be either attribute certificates (limiting      authorizations) or public key certificates (limiting path      validation).  The issuerSerial field (in the ESSCertIDv2      structure) SHOULD be present for these certificates, unless the      client who is validating the signature is expected to have easy      access to all the certificates required for validation.  If only      the signing certificate is present in the sequence, there are no      restrictions on the set of certificates used in validating the      signature.Schaad                      Standards Track                     [Page 4]

RFC 5035                    ESSCertID Update                 August 2007   policies      contains a sequence of policy information terms that identify      those certificate policies that the signer asserts apply to the      certificate, and under which the certificate should be relied      upon.  This value suggests a policy value to be used in the      relying party's certification path validation.  The definition of      PolicyInformation can be found in [RFC3280].   If present, the SigningCertificateV2 attribute MUST be a signed   attribute; it MUST NOT be an unsigned attribute.  CMS defines   SignedAttributes as a SET OF Attribute.  A SignerInfo MUST NOT   include multiple instances of the SigningCertificateV2 attribute.   CMS defines the ASN.1 syntax for the signed attributes to include   attrValues SET OF AttributeValue.  A SigningCertificateV2 attribute   MUST include only a single instance of AttributeValue.  There MUST   NOT be zero or multiple instances of AttributeValue present in the   attrValues SET OF AttributeValue.4.  Insert NewSection 5.4.1.1 'Certificate Identification Version 2'   Insert the following text as a new section.   5.4.1.1 Certificate Identification Version 2   The best way to identify certificates is an often-discussed issue.   The ESSCertIDv2 structure supplies two different fields that are used   for this purpose.   The hash of the entire certificate allows for a verifier to check   that the certificate used in the verification process was the same   certificate the signer intended.  Hashes are convenient in that they   are frequently used by certificate stores as a method of indexing and   retrieving certificates as well.  The use of the hash is required by   this structure since the detection of substituted certificates is   based on the fact they would map to different hash values.   The issuer/serial number pair is the method of identification of   certificates used in [RFC3280].  That document imposes a restriction   for certificates that the issuer distinguished name must be present.   The issuer/serial number pair would therefore normally be sufficient   to identify the correct signing certificate.  (This assumes the same   issuer name is not reused from the set of trust anchors.)  The   issuer/serial number pair can be stored in the sid field of the   SignerInfo object.  However, the sid field is not covered by the   signature.  In the cases where the issuer/serial number pair is not   used in the sid or the issuer/serial number pair needs to be signed,   it SHOULD be placed in the issuerSerial field of the ESSCertIDv2   structure.Schaad                      Standards Track                     [Page 5]

RFC 5035                    ESSCertID Update                 August 2007   Attribute certificates and additional public key certificates   containing information do not have an issuer/serial number pair   represented anywhere in a SignerInfo object.  When an attribute   certificate or an additional public key certificate is not included   in the SignedData object, it becomes much more difficult to get the   correct set of certificates based only on a hash of the certificate.   For this reason, these certificates SHOULD be identified by the   IssuerSerial object.   This document defines a certificate identifier as:        ESSCertIDv2 ::=  SEQUENCE {            hashAlgorithm           AlgorithmIdentifier                   DEFAULT {algorithm id-sha256},            certHash                 Hash,            issuerSerial             IssuerSerial OPTIONAL        }        Hash ::= OCTET STRING        IssuerSerial ::= SEQUENCE {            issuer                   GeneralNames,            serialNumber             CertificateSerialNumber       }   The fields of ESSCertIDv2 are defined as follows:   hashAlgorithm      contains the identifier of the algorithm used in computing      certHash.   certHash      is computed over the entire DER-encoded certificate (including the      signature) using the SHA-1 algorithm.   issuerSerial      holds the identification of the certificate.  The issuerSerial      would normally be present unless the value can be inferred from      other information (e.g., the sid field of the SignerInfo object).   The fields of IssuerSerial are defined as follows:   issuer      contains the issuer name of the certificate.  For non-attribute      certificates, the issuer MUST contain only the issuer name from      the certificate encoded in the directoryName choice of      GeneralNames.  For attribute certificates, the issuer MUST contain      the issuer name field from the attribute certificate.Schaad                      Standards Track                     [Page 6]

RFC 5035                    ESSCertID Update                 August 2007   serialNumber      holds the serial number that uniquely identifies the certificate      for the issuer.5.  Insert NewSection 5.4.2 'Signing Certificate Attribute Definition    Version 1'   (Note: This section does not present new material.  This section   contains the original contents of Section 5.4 in [ESS], which are   retained with minor changes in this specification to achieve   backwards compatibility.)   Insert the following text as a new section.   5.4.2 Signing Certificate Attribute Definition Version 1   The signing certificate attribute is designed to prevent the simple   substitution and re-issue attacks, and to allow for a restricted set   of certificates to be used in verifying a signature.   The definition of SigningCertificate is       SigningCertificate ::=  SEQUENCE {           certs        SEQUENCE OF ESSCertID,           policies     SEQUENCE OF PolicyInformation OPTIONAL       }       id-aa-signingCertificate OBJECT IDENTIFIER ::= { iso(1)           member-body(2) us(840) rsadsi(113549) pkcs(1) pkcs9(9)           smime(16) id-aa(2) 12 }   The first certificate identified in the sequence of certificate   identifiers MUST be the certificate used to verify the signature.   The encoding of the ESSCertID for this certificate SHOULD include the   issuerSerial field.  If other constraints ensure that   issuerAndSerialNumber will be present in the SignerInfo, the   issuerSerial field MAY be omitted.  The certificate identified is   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.   If more than one certificate is present in the sequence of   ESSCertIDs, the certificates after the first one limit the set of   certificates that are used during validation.  Certificates can be   either attribute certificates (limiting authorizations) or public key   certificates (limiting path validation).  The issuerSerial field (in   the ESSCertID structure) SHOULD be present for these certificates,   unless the client who is validating the signature is expected to haveSchaad                      Standards Track                     [Page 7]

RFC 5035                    ESSCertID Update                 August 2007   easy access to all the certificates required for validation.  If only   the signing certificate is present in the sequence, there are no   restrictions on the set of certificates used in validating the   signature.   The sequence of policy information terms identifies those certificate   policies that the signer asserts apply to the certificate, and under   which the certificate should be relied upon.  This value suggests a   policy value to be used in the relying party's certification path   validation.   If present, the SigningCertificate attribute MUST be a signed   attribute; it MUST NOT be an unsigned attribute.  Cryptographic   Message Syntax (CMS) defines SignedAttributes as a SET OF Attribute.   A SignerInfo MUST NOT include multiple instances of the   SigningCertificate attribute.  CMS defines the ASN.1 syntax for the   signed attributes to include attrValues SET OF AttributeValue.  A   SigningCertificate attribute MUST include only a single instance of   AttributeValue.  There MUST NOT be zero or multiple instances of   AttributeValue present in the attrValues SET OF AttributeValue.6.  Insert NewSection 5.4.2.1 'Certificate Identification Version 1'   (Note: This section does not present new material.  This section   contains the original contents of Section 5.4 in [ESS], which are   retained with minor changes in this specification to achieve   backwards compatibility.)   Delete oldSection 5.4.1   Insert the following as new text   5.4.2.1 Certificate Identification Version 1   Certificates are uniquely identified using the information in the   ESSCertID structure.  Discussion can be found inSection 5.4.1.1.   This document defines a certificate identifier as:       ESSCertID ::=  SEQUENCE {            certHash                 Hash,            issuerSerial             IssuerSerial OPTIONAL       }Schaad                      Standards Track                     [Page 8]

RFC 5035                    ESSCertID Update                 August 2007   The fields of ESSCertID are defined as follows:   certHash      is computed over the entire DER-encoded certificate (including the      signature).   issuerSerial      holds the identification of the certificate.  This field would      normally be present unless the value can be inferred from other      information (e.g., the sid field of the SignerInfo object).   The fields of IssuerSerial are discussed inSection 5.4.1.17.  Security Considerations   This document is designed to address the security issue of a   substituted certificate used by the validator.  If a different   certificate is used by the validator than the signer, the validator   may not get the correct result.  An example of this would be that the   original certificate was revoked and a new certificate with the same   public key was issued for a different individual.  Since the issuer/   serial number field is not protected, the attacker could replace this   and point to the new certificate and validation would be successful.   The attributes defined in this document are to be placed in locations   that are protected by the signature.  This attribute does not provide   any additional security if placed in an unsigned or un-authenticated   location.   The attributes defined in this document permit a signer to select a   hash algorithm to identify a certificate.  A poorly selected hash   algorithm may provide inadequate protection against certificate   substitution or result in denial of service for this protection.  By   employing the attributes defined in this specification with the same   hash algorithm used for message signing, the sender can ensure that   these attributes provide commensurate security.   Since recipients must support the hash algorithm to verify the   signature, selecting the same hash algorithm also increases the   likelihood that the hash algorithm is supported in the context of   certificate identification.  Note that an unsupported hash algorithm   for certificate identification does not preclude validating the   message but does deny the message recipient protection against   certificate substitution.   To ensure that legacy implementations are provided protection against   certificate substitution, clients are permitted to include both   ESScertID and ESScertIDv2 in the same message.  Since theseSchaad                      Standards Track                     [Page 9]

RFC 5035                    ESSCertID Update                 August 2007   attributes are generated and evaluated independently, the contents   could conceivably be in conflict.  Specifically, where a signer has   multiple certificates containing the same public key, the two   attributes could specify different signing certificates.  The result   of signature processing may vary depending on which certificate is   used to validate the signature.   Recipients that attempt to evaluate both attributes may choose to   reject such a message.8.  Normative References   [ESS]      Hoffman, P., "Enhanced Security Services for S/MIME",RFC 2634, June 1999.   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate              Requirement Levels",RFC 2119,BCP 14, March 1997.   [RFC3280]  Housley, R., Ford, W., Polk, W., and D. Solo, "Internet              X.509 Public Key Infrastructure Certificate and              Certificate Revocation List (CRL) Profile",RFC 3280,              April 2002.   [RFC3852]  Housley, R., "Cryptographic Message Syntax (CMS)",RFC 3852, July 2004.   [UTF8]     Yergeau, F., "UTF-8, a transformation format of ISO              10646", STD 63,RFC 3629, November 2003.Schaad                      Standards Track                    [Page 10]

RFC 5035                    ESSCertID Update                 August 2007Appendix A.  ASN.1 Module   Replace the ASN.1 module inRFC 2634 with this one.ExtendedSecurityServices-2006      { iso(1) member-body(2) us(840) rsadsi(113549)        pkcs(1) pkcs-9(9) smime(16) modules(0) id-mod-ess-2006(30) }DEFINITIONS IMPLICIT TAGS ::=BEGINIMPORTS-- Cryptographic Message Syntax (CMS) [RFC3852]    ContentType, IssuerAndSerialNumber, SubjectKeyIdentifier       FROM CryptographicMessageSyntax2004 { iso(1) member-body(2)                us(840) rsadsi(113549) pkcs(1) pkcs-9(9) smime(16)                modules(0) cms-2004(24)}-- PKIX Certificate and CRL Profile, Section A.1 Explicity Tagged Module--  1988 Syntax             [RFC3280]    AlgorithmIdentifier, CertificateSerialNumber       FROM PKIX1Explicit88 { iso(1) identified-organization(3) dod(6)                internet(1) security(5) mechanisms(5) pkix(7) id-mod(0)                id-pkix1-explicit(18) }-- PKIX Certificate and CRL Profile, Sec A.2 Implicitly Tagged Module,--  1988 Syntax             [RFC3280]    PolicyInformation, GeneralNames          FROM PKIX1Implicit88 {iso(1) identified-organization(3) dod(6)                internet(1) security(5) mechanisms(5) pkix(7) id-mod(0)                id-pkix1-implicit(19)};-- Extended Security Services-- The construct "SEQUENCE SIZE (1..MAX) OF" appears in several ASN.1-- constructs in this module.  A valid ASN.1 SEQUENCE can have zero or-- more entries.  The SIZE (1..MAX) construct constrains the SEQUENCE to-- have at least one entry.  MAX indicates the upper bound is-- unspecified.  Implementations are free to choose an upper bound that-- suits their environment.-- UTF8String ::= [UNIVERSAL 12] IMPLICIT OCTET STRING-- The contents are formatted as described in [UTF8]--Section 2.7ReceiptRequest ::= SEQUENCE {  signedContentIdentifier ContentIdentifier,  receiptsFrom ReceiptsFrom,  receiptsTo SEQUENCE SIZE (1..ub-receiptsTo) OF GeneralNames}Schaad                      Standards Track                    [Page 11]

RFC 5035                    ESSCertID Update                 August 2007ub-receiptsTo INTEGER ::= 16id-aa-receiptRequest OBJECT IDENTIFIER ::= { iso(1) member-body(2)    us(840) rsadsi(113549) pkcs(1) pkcs-9(9) smime(16) id-aa(2) 1}ContentIdentifier ::= OCTET STRINGid-aa-contentIdentifier OBJECT IDENTIFIER ::= { iso(1) member-body(2)    us(840) rsadsi(113549) pkcs(1) pkcs-9(9) smime(16) id-aa(2) 7}ReceiptsFrom ::= CHOICE { allOrFirstTier [0] AllOrFirstTier, -- formerly "allOrNone [0]AllOrNone" receiptList [1] SEQUENCE OF GeneralNames}AllOrFirstTier ::= INTEGER { -- Formerly AllOrNone allReceipts (0), firstTierRecipients (1)}--Section 2.8Receipt ::= SEQUENCE {  version ESSVersion,  contentType ContentType,  signedContentIdentifier ContentIdentifier,  originatorSignatureValue OCTET STRING}id-ct-receipt OBJECT IDENTIFIER ::= { iso(1) member-body(2) us(840)   rsadsi(113549) pkcs(1) pkcs-9(9) smime(16) id-ct(1) 1}ESSVersion ::= INTEGER  { v1(1) }--Section 2.9ContentHints ::= SEQUENCE {  contentDescription UTF8String (SIZE (1..MAX)) OPTIONAL,  contentType ContentType}id-aa-contentHint OBJECT IDENTIFIER ::= { iso(1) member-body(2) us(840)    rsadsi(113549) pkcs(1) pkcs-9(9) smime(16) id-aa(2) 4}--Section 2.10MsgSigDigest ::= OCTET STRINGSchaad                      Standards Track                    [Page 12]

RFC 5035                    ESSCertID Update                 August 2007id-aa-msgSigDigest OBJECT IDENTIFIER ::= { iso(1) member-body(2)   us(840) rsadsi(113549) pkcs(1) pkcs-9(9) smime(16) id-aa(2) 5}--Section 2.11ContentReference ::= SEQUENCE {  contentType ContentType,  signedContentIdentifier ContentIdentifier,  originatorSignatureValue OCTET STRING}id-aa-contentReference   OBJECT IDENTIFIER ::= { iso(1) member-body(2)    us(840) rsadsi(113549) pkcs(1) pkcs-9(9) smime(16) id-aa(2) 10 }--Section 3.2ESSSecurityLabel ::= SET {  security-policy-identifier SecurityPolicyIdentifier,  security-classification SecurityClassification OPTIONAL,  privacy-mark ESSPrivacyMark OPTIONAL,  security-categories SecurityCategories OPTIONAL}id-aa-securityLabel OBJECT IDENTIFIER ::= { iso(1) member-body(2)    us(840) rsadsi(113549) pkcs(1) pkcs-9(9) smime(16) id-aa(2) 2}SecurityPolicyIdentifier ::= OBJECT IDENTIFIERSecurityClassification ::= INTEGER {  unmarked (0),  unclassified (1),  restricted (2),  confidential (3),  secret (4),  top-secret (5)}(0..ub-integer-options)ub-integer-options INTEGER ::= 256ESSPrivacyMark ::= CHOICE {    pString      PrintableString (SIZE (1..ub-privacy-mark-length)),    utf8String   UTF8String (SIZE (1..MAX))}ub-privacy-mark-length INTEGER ::= 128SecurityCategories ::= SET SIZE (1..ub-security-categories) OF        SecurityCategorySchaad                      Standards Track                    [Page 13]

RFC 5035                    ESSCertID Update                 August 2007ub-security-categories INTEGER ::= 64SecurityCategory ::= SEQUENCE {  type  [0] OBJECT IDENTIFIER,  value [1] ANY DEFINED BY type}--Note: The aforementioned SecurityCategory syntax produces identical--hex encodings as the following SecurityCategory syntax that is--documented in the X.411 specification:----SecurityCategory ::= SEQUENCE {--     type  [0]  SECURITY-CATEGORY,--     value [1]  ANY DEFINED BY type }----SECURITY-CATEGORY MACRO ::=--BEGIN--TYPE NOTATION ::= type | empty--VALUE NOTATION ::= value (VALUE OBJECT IDENTIFIER)--END--Section 3.4EquivalentLabels ::= SEQUENCE OF ESSSecurityLabelid-aa-equivalentLabels OBJECT IDENTIFIER ::= { iso(1) member-body(2)    us(840) rsadsi(113549) pkcs(1) pkcs-9(9) smime(16) id-aa(2) 9}--Section 4.4MLExpansionHistory ::= SEQUENCE      SIZE (1..ub-ml-expansion-history) OF MLDataid-aa-mlExpandHistory OBJECT IDENTIFIER ::= { iso(1) member-body(2)    us(840) rsadsi(113549) pkcs(1) pkcs-9(9) smime(16) id-aa(2) 3 }ub-ml-expansion-history INTEGER ::= 64  MLData ::= SEQUENCE {  mailListIdentifier EntityIdentifier,  expansionTime GeneralizedTime,  mlReceiptPolicy MLReceiptPolicy OPTIONAL}EntityIdentifier ::= CHOICE {  issuerAndSerialNumber IssuerAndSerialNumber,  subjectKeyIdentifier SubjectKeyIdentifier}Schaad                      Standards Track                    [Page 14]

RFC 5035                    ESSCertID Update                 August 2007MLReceiptPolicy ::= CHOICE {  none [0] NULL,  insteadOf [1] SEQUENCE SIZE (1..MAX) OF GeneralNames,  inAdditionTo [2] SEQUENCE SIZE (1..MAX) OF GeneralNames}--Section 5.4SigningCertificate ::=  SEQUENCE {    certs        SEQUENCE OF ESSCertID,    policies     SEQUENCE OF PolicyInformation OPTIONAL}id-aa-signingCertificate OBJECT IDENTIFIER ::= { iso(1)    member-body(2) us(840) rsadsi(113549) pkcs(1) pkcs9(9)    smime(16) id-aa(2) 12 }SigningCertificateV2 ::=  SEQUENCE {    certs        SEQUENCE OF ESSCertIDv2,    policies     SEQUENCE OF PolicyInformation OPTIONAL}id-aa-signingCertificateV2 OBJECT IDENTIFIER ::= { iso(1)    member-body(2) us(840) rsadsi(113549) pkcs(1) pkcs9(9)    smime(16) id-aa(2) 47 }id-sha256  OBJECT IDENTIFIER  ::=  { joint-iso-itu-t(2)    country(16) us(840) organization(1) gov(101)    csor(3) nistalgorithm(4) hashalgs(2) 1 }ESSCertIDv2 ::= SEQUENCE {     hashAlgorithm           AlgorithmIdentifier            DEFAULT {algorithm id-sha256},     certHash                Hash,     issuerSerial            IssuerSerial OPTIONAL}ESSCertID ::=  SEQUENCE {     certHash                 Hash,     issuerSerial             IssuerSerial OPTIONAL}Hash ::= OCTET STRING  IssuerSerial ::= SEQUENCE {     issuer                   GeneralNames,     serialNumber             CertificateSerialNumber}ENDSchaad                      Standards Track                    [Page 15]

RFC 5035                    ESSCertID Update                 August 2007-- of ExtendedSecurityServices-2006Author's Address   Jim Schaad   Soaring Hawk Consulting   PO Box 675   Gold Bar, WA  98251   EMail: jimsch@exmsft.comSchaad                      Standards Track                    [Page 16]

RFC 5035                    ESSCertID Update                 August 2007Full Copyright Statement   Copyright (C) The IETF Trust (2007).   This document is subject to the rights, licenses and restrictions   contained inBCP 78, and except as set forth therein, the authors   retain all their rights.   This document and the information contained herein are provided on an   "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS   OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND   THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS   OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF   THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED   WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.Intellectual Property   The IETF takes no position regarding the validity or scope of any   Intellectual Property Rights or other rights that might be claimed to   pertain to the implementation or use of the technology described in   this document or the extent to which any license under such rights   might or might not be available; nor does it represent that it has   made any independent effort to identify any such rights.  Information   on the procedures with respect to rights in RFC documents can be   found inBCP 78 andBCP 79.   Copies of IPR disclosures made to the IETF Secretariat and any   assurances of licenses to be made available, or the result of an   attempt made to obtain a general license or permission for the use of   such proprietary rights by implementers or users of this   specification can be obtained from the IETF on-line IPR repository athttp://www.ietf.org/ipr.   The IETF invites any interested party to bring to its attention any   copyrights, patents or patent applications, or other proprietary   rights that may cover technology that may be required to implement   this standard.  Please address the information to the IETF at   ietf-ipr@ietf.org.Schaad                      Standards Track                    [Page 17]