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rfc:rfc5126

Table of Contents

Network Working Group D. Pinkas Request for Comments: 5126 Bull SAS Obsoletes: 3126 N. Pope Category: Informational Thales eSecurity

                                                               J. Ross
                                                Security and Standards
                                                         February 2008
             CMS Advanced Electronic Signatures (CAdES)

Status of This Memo

 This memo provides information for the Internet community.  It does
 not specify an Internet standard of any kind.  Distribution of this
 memo is unlimited.

Abstract

 This document 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
 (i.e., repudiates) the validity of the signature.
 The format can be considered as an extension to RFC 3852 and RFC
 2634, where, when appropriate, additional signed and unsigned
 attributes have been defined.
 The contents of this Informational RFC amount to a transposition of
 the ETSI Technical Specification (TS) 101 733 V.1.7.4 (CMS Advanced
 Electronic Signatures -- CAdES) and is technically equivalent to it.
 The technical contents of this specification are maintained by ETSI.
 The ETSI TS and further updates are available free of charge at:
 http://www.etsi.org/WebSite/Standards/StandardsDownload.aspx

Pinkas, et al. Informational [Page 1] RFC 5126 CMS Advanced Electronic Signatures February 2008

Table of Contents

 1. Introduction ....................................................6
 2. Scope ...........................................................6
 3. Definitions and Abbreviations ...................................8
    3.1. Definitions ................................................8
    3.2. Abbreviations .............................................11
 4. Overview .......................................................12
    4.1. Major Parties .............................................13
    4.2. Signature Policies ........................................14
    4.3. Electronic Signature Formats ..............................15
         4.3.1. CAdES Basic Electronic Signature (CAdES-BES) .......15
         4.3.2. CAdES Explicit Policy-based Electronic
                Signatures (CAdES-EPES) ............................18
    4.4. Electronic Signature Formats with Validation Data .........19
         4.4.1. Electronic Signature with Time (CAdES-T) ...........20
         4.4.2. ES with Complete Validation Data References
                (CAdES-C) ..........................................21
         4.4.3. Extended Electronic Signature Formats ..............23
                4.4.3.1. EXtended Long Electronic Signature
                         (CAdES-X Long) ............................24
                4.4.3.2. EXtended Electronic Signature with
                         Time Type 1 ...............................25
                4.4.3.3. EXtended Electronic Signature with
                         Time Type 2 ...............................26
                4.4.3.4. EXtended Long Electronic Signature
                         with Time (CAdES-X Long ...................27
         4.4.4. Archival Electronic Signature (CAdES-A) ............27
    4.5. Arbitration ...............................................28
    4.6. Validation Process ........................................29
 5. Electronic Signature Attributes ................................30
    5.1. General Syntax ............................................30
    5.2. Data Content Type .........................................30
    5.3. Signed-data Content Type ..................................30
    5.4. SignedData Type ...........................................31
    5.5. EncapsulatedContentInfo Type ..............................31
    5.6. SignerInfo Type ...........................................31
         5.6.1. Message Digest Calculation Process .................32
         5.6.2. Message Signature Generation Process ...............32
         5.6.3. Message Signature Verification Process .............32
    5.7. Basic ES Mandatory Present Attributes .....................32
         5.7.1. content-type .......................................32
         5.7.2. Message Digest .....................................33
         5.7.3. Signing Certificate Reference Attributes ...........33
                5.7.3.1. ESS signing-certificate Attribute
                         Definition ................................34
                5.7.3.2. ESS signing-certificate-v2
                         Attribute Definition ......................34

Pinkas, et al. Informational [Page 2] RFC 5126 CMS Advanced Electronic Signatures February 2008

                5.7.3.3. Other signing-certificate
                         Attribute Definition ......................35
    5.8. Additional Mandatory Attributes for Explicit
         Policy-based Electronic Signatures ........................36
         5.8.1. signature-policy-identifier ........................36
    5.9. CMS Imported Optional Attributes ..........................38
         5.9.1. signing-time .......................................38
         5.9.2. countersignature ...................................39
    5.10. ESS-Imported Optional Attributes .........................39
         5.10.1. content-reference Attribute .......................39
         5.10.2. content-identifier Attribute ......................39
         5.10.3. content-hints Attribute ...........................40
    5.11. Additional Optional Attributes Defined in the
          Present Document .........................................40
         5.11.1. commitment-type-indication Attribute ..............41
         5.11.2. signer-location Attribute .........................43
         5.11.3. signer-attributes Attribute .......................43
         5.11.4. content-time-stamp Attribute ......................44
    5.12. Support for Multiple Signatures ..........................44
         5.12.1. Independent Signatures ............................44
         5.12.2. Embedded Signatures ...............................45
 6. Additional Electronic Signature Validation Attributes ..........45
    6.1. signature time-stamp Attribute (CAdES-T) ..................47
         6.1.1. signature-time-stamp Attribute Definition ..........47
    6.2. Complete Validation Data References (CAdES-C) .............48
         6.2.1. complete-certificate-references Attribute
                Definition .........................................48
         6.2.2. complete-revocation-references Attribute
                Definition .........................................49
         6.2.3. attribute-certificate-references Attribute
                Definition .........................................51
         6.2.4. attribute-revocation-references Attribute
                Definition .........................................52
    6.3. Extended Validation Data (CAdES-X) ........................52
         6.3.1. Time-Stamped Validation Data (CAdES-X Type
                1 or Type 2) .......................................53
         6.3.2. Long Validation Data (CAdES-X Long, CAdES-X
                Long Type 1 or 2) ..................................53
         6.3.3. certificate-values Attribute Definition ............54
         6.3.4. revocation-values Attribute Definition .............54
         6.3.5. CAdES-C-time-stamp Attribute Definition ............56
         6.3.6. time-stamped-certs-crls-references
                Attribute Definition ...............................57
    6.4. Archive Validation Data ...................................58
         6.4.1. archive-time-stamp Attribute Definition ............58
 7. Other Standard Data Structures .................................60
    7.1. Public Key Certificate Format .............................60
    7.2. Certificate Revocation List Format ........................60

Pinkas, et al. Informational [Page 3] RFC 5126 CMS Advanced Electronic Signatures February 2008

    7.3. OCSP Response Format ......................................60
    7.4. Time-Stamp Token Format ...................................60
    7.5. Name and Attribute Formats ................................60
    7.6. AttributeCertificate ......................................61
 8. Conformance Requirements .......................................61
    8.1. CAdES-Basic Electronic Signature (CAdES-BES) ..............62
    8.2. CAdES-Explicit Policy-based Electronic Signature ..........63
    8.3. Verification Using Time-Stamping ..........................63
    8.4. Verification Using Secure Records .........................63
 9. References .....................................................64
    9.1. Normative References ......................................64
    9.2. Informative References ....................................65
 Annex A (normative): ASN.1 Definitions ............................69
         A.1. Signature Format Definitions Using
              X.208 ASN.1 Syntax ...................................69
         A.2. Signature Format Definitions Using
              X.680 ASN.1 Syntax ...................................77
 Annex B (informative): Extended Forms of Electronic Signatures ....86
         B.1. Extended Forms of Validation Data ....................86
              B.1.1. CAdES-X Long ..................................87
              B.1.2. CAdES-X Type 1 ................................88
              B.1.3. CAdES-X Type 2 ................................90
              B.1.4. CAdES-X Long Type 1 and CAdES-X Long Type 2 ...91
         B.2. Time-Stamp Extensions ................................93
         B.3. Archive Validation Data (CAdES-A) ....................94
         B.4. Example Validation Sequence ..........................97
         B.5. Additional Optional Features ........................102
 Annex C (informative): General Description .......................103
         C.1. The Signature Policy ................................103
         C.2. Signed Information ..................................104
         C.3. Components of an Electronic Signature ...............104
              C.3.1. Reference to the Signature Policy ............104
              C.3.2. Commitment Type Indication ...................105
              C.3.3. Certificate Identifier from the Signer .......106
              C.3.4. Role Attributes ..............................106
                     C.3.4.1.  Claimed Role .......................107
                     C.3.4.2.  Certified Role .....................107
              C.3.5. Signer Location ..............................108
              C.3.6. Signing Time .................................108
              C.3.7. Content Format ...............................108
              C.3.8. content-hints ................................109
              C.3.9. Content Cross-Referencing ....................109
         C.4. Components of Validation Data .......................109
              C.4.1. Revocation Status Information ................109
                     C.4.1.1. CRL Information .....................110
                     C.4.1.2. OCSP Information ....................110
              C.4.2. Certification Path ...........................111
              C.4.3. Time-stamping for Long Life of Signatures ....111

Pinkas, et al. Informational [Page 4] RFC 5126 CMS Advanced Electronic Signatures February 2008

              C.4.4. Time-stamping for Long Life of Signature
                     before CA key Compromises ....................113
                      C.4.4.1. Time-stamping the ES with
                               Complete Validation Data ...........113
                      C.4.4.2. Time-Stamping Certificates and
                               Revocation Information References ..114
              C.4.5. Time-stamping for Archive of Signature .......115
              C.4.6. Reference to Additional Data .................116
              C.4.7. Time-Stamping for Mutual Recognition .........116
              C.4.8. TSA Key Compromise ...........................117
         C.5. Multiple Signatures .................................118
 Annex D (informative): Data Protocols to Interoperate with TSPs ..118
         D.1. Operational Protocols ...............................118
              D.1.1. Certificate Retrieval ........................118
              D.1.2. CRL Retrieval ................................118
              D.1.3. Online Certificate Status ....................119
              D.1.4. Time-Stamping ................................119
         D.2. Management Protocols ................................119
              D.2.1. Request for Certificate Revocation ...........119
 Annex E (informative): Security Considerations ...................119
         E.1. Protection of Private Key ...........................119
         E.2. Choice of Algorithms ................................119
 Annex F (informative): Example Structured Contents and MIME ......120
         F.1. General Description .................................120
              F.1.1. Header Information ...........................120
              F.1.2. Content Encoding .............................121
              F.1.3. Multi-Part Content ...........................121
         F.2. S/MIME ..............................................122
              F.2.1. Using application/pkcs7-mime .................123
              F.2.2. Using application/pkcs7-signature ............124
 Annex G (informative): Relationship to the European Directive
                        and EESSI .................................125
         G.1. Introduction ........................................125
         G.2. Electronic Signatures and the Directive .............126
         G.3. ETSI Electronic Signature Formats and the Directive .127
         G.4. EESSI Standards and Classes of Electronic Signature .127
              G.4.1. Structure of EESSI Standardization ...........127
              G.4.2. Classes of Electronic Signatures .............128
              G.4.3. Electronic Signature Classes and the ETSI
                     Electronic Signature Format ..................128
 Annex H (informative): APIs for the Generation and Verification
                        of Electronic Signatures Tokens ...........129
         H.1. Data Framing ........................................129
         H.2. IDUP-GSS-APIs Defined by the IETF ...................131
         H.3. CORBA Security Interfaces Defined by the OMG ........132
 Annex I (informative): Cryptographic Algorithms ..................133
         I.1. Digest Algorithms ...................................133
              I.1.1. SHA-1 ........................................133

Pinkas, et al. Informational [Page 5] RFC 5126 CMS Advanced Electronic Signatures February 2008

              I.1.2. General ......................................133
         I.2. Digital Signature Algorithms ........................134
              I.2.1. DSA ..........................................134
              I.2.2. RSA ..........................................135
              I.2.3. General ......................................135
 Annex J (informative): Guidance on Naming ........................137
         J.1. Allocation of Names .................................137
         J.2. Providing Access to Registration Information ........138
         J.3. Naming Schemes ......................................138
              J.3.1. Naming Schemes for Individual Citizens .......138
              J.3.2. Naming Schemes for Employees of an
                     Organization .................................139

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.  This includes
 evidence as to its validity even if the signer or verifying party
 later attempts to deny (i.e., repudiates; see ISO/IEC 10181-5
 [ISO10181-5]) the validity of the signature.
 Thus, the present document can be used for any transaction between an
 individual and a company, between two companies, between an
 individual and a governmental body, etc.  The present document is
 independent of any environment; it can be applied to any environment,
 e.g., smart cards, Global System for Mobile Communication Subscriber
 Identity Module (GSM SIM) cards, special programs for electronic
 signatures, etc.
 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 present document, is a form
 of advanced electronic signature, as defined in the Directive.

2. Scope

 The scope of the present document covers electronic signature formats
 only.  The aspects of Electronic Signature Policies are defined in
 RFC 3125 [RFC3125] and ETSI TR 102 272 [TR102272].
 The present document defines a number of electronic signature
 formats, including electronic signatures that can remain valid over
 long periods.  This includes evidence as to its validity even if the

Pinkas, et al. Informational [Page 6] RFC 5126 CMS Advanced Electronic Signatures February 2008

 signer or verifying party later attempts to deny (repudiates) the
 validity of the electronic signature.
 The present document specifies use of Trusted Service Providers
 (e.g., Time-Stamping Authorities) 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, as defined by the present 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.
 The present document includes the concept of signature policies that
 can be used to establish technical consistency when validating
 electronic signatures, but it does not mandate their use.
 The present document is based on the use of public key cryptography
 to produce digital signatures, supported by public key certificates.
 The present document also specifies the use of time-stamping and
 time-marking services to prove the validity of a signature long after
 the normal lifetime of critical elements of an electronic signature.
 This document also, as an option, defines ways to provide very
 long-term protection against key compromise or weakened algorithms.
 The present document builds on existing standards that are widely
 adopted.  These include:
  1. RFC 3852 [4]: "Cryptographic Message Syntax (CMS)";
  1. ISO/IEC 9594-8/ITU-T Recommendation X.509 [1]: "Information

technology - Open Systems Interconnection - The Directory:

      Authentication framework";
  1. RFC 3280 [2]: "Internet X.509 Public Key Infrastructure (PKIX)

Certificate and Certificate Revocation List (CRL) Profile";

  1. RFC 3161 [7]: "Internet X.509 Public Key Infrastructure

Time-Stamp Protocol (TSP)".

    NOTE: See Section 11 for a full set of references.
 The present document describes formats for advanced electronic
 signatures using ASN.1 (Abstract Syntax Notation 1) [14].  ASN.1 is
 encoded using X.690 [16].
 These formats are based on CMS (Cryptographic Message Syntax) defined
 in RFC 3852 [4].  These electronic signatures are thus called CAdES,
 for "CMS Advanced Electronic Signatures".

Pinkas, et al. Informational [Page 7] RFC 5126 CMS Advanced Electronic Signatures February 2008

 Another document, TS 101 903 [TS101903], describes formats for XML
 advanced electronic signatures (XAdES) built on XMLDSIG as specified
 in [XMLDSIG].
 In addition, the present document identifies other documents that
 define formats for Public Key Certificates, Attribute Certificates,
 and Certificate Revocation Lists and supporting protocols, including
 protocols for use by trusted third parties to support the operation
 of electronic signature creation and validation.
 Informative annexes include:
  1. illustrations of extended forms of Electronic Signature formats

that protect against various vulnerabilities and examples of

      validation processes (Annex B);
  1. descriptions and explanations of some of the concepts used in

the present document, giving a rationale for normative parts of

      the present document (Annex C);
  1. information on protocols to interoperate with Trusted Service

Providers (Annex D);

  1. guidance on naming (Annex E);
  1. an example structured content and MIME (Annex F);
  1. the relationship between the present document and the directive

on electronic signature and associated standardization

      initiatives (Annex G);
  1. APIs to support the generation and verification of electronic

signatures (Annex H);

  1. cryptographic algorithms that may be used (Annex I); and
  1. naming schemes (see Annex J).

3. Definitions and Abbreviations

3.1. Definitions

 For the purposes of the present document, the following terms and
 definitions apply:
 Arbitrator: an arbitrator entity may be used to arbitrate a dispute
 between a signer and verifier when there is a disagreement on the
 validity of a digital signature.

Pinkas, et al. Informational [Page 8] RFC 5126 CMS Advanced Electronic Signatures February 2008

 Attribute Authority (AA): an authority that assigns privileges by
 issuing attribute certificates.
 Authority Certificate: a certificate issued to an authority (e.g.,
 either to a certification authority or an attribute authority).
 Attribute Authority Revocation List (AARL): a revocation list
 containing a list of references to certificates issued to AAs that
 are no longer considered valid by the issuing authority.
 Attribute Certificate Revocation List (ACRL): a revocation list
 containing a list of references to attribute certificates that are no
 longer considered valid by the issuing authority.
 Certification Authority Revocation List (CARL): a revocation list
 containing a list of public key certificates issued to certification
 authorities that are no longer considered valid by the certificate
 issuer.
 Certification Authority (CA): an authority trusted by one or more
 users to create and assign public key certificates; optionally, the
 certification authority may create the users' keys.
    NOTE: See ITU-T Recommendation X.509 [1].
 Certificate Revocation List (CRL): a signed list indicating a set of
 public key certificates that are no longer considered valid by the
 certificate issuer.
 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.
    NOTE: See ISO 7498-2 [ISO7498-2].
 Electronic Signature: data in electronic form that is attached to or
 logically associated with other electronic data and that serves as a
 method of authentication.
    NOTE: See Directive 1999/93/EC of the European Parliament and of
    the Council of 13 December 1999 on a Community framework for
    electronic signatures [EUDirective].
 Extended Electronic Signatures: electronic signatures enhanced by
 complementing the baseline requirements with additional data, such as
 time-stamp tokens and certificate revocation data, to address
 commonly recognized threats.

Pinkas, et al. Informational [Page 9] RFC 5126 CMS Advanced Electronic Signatures February 2008

 Explicit Policy-based Electronic Signature (EPES): an electronic
 signature where the signature policy that shall be used to validate
 it is explicitly specified.
 Grace Period: a time period that permits the certificate revocation
 information to propagate through the revocation process to relying
 parties.
 Initial Verification: a process performed by a verifier done after an
 electronic signature is generated in order to capture additional
 information that could make it valid for long-term verification.
 Public Key Certificate (PKC): public keys of a user, together with
 some other information, rendered unforgeable by encipherment with the
 private key of the certification authority that issued it.
    NOTE: See ITU-T Recommendation X.509 [1].
 Rivest-Shamir-Adleman (RSA): an asymmetric cryptography algorithm
 based on the difficulty to factor very large numbers using a key
 pair: a private key and a public key.
 Signature Policy: a set of rules for the creation and validation of
 an electronic signature that defines the technical and procedural
 requirements for electronic signature creation and validation, in
 order to meet a particular business need, and under which the
 signature can be determined to be valid.
 Signature Policy Issuer: an entity that defines and issues a
 signature policy.
 Signature Validation Policy: part of the signature policy that
 specifies the technical requirements on the signer in creating a
 signature and verifier when validating a signature.
 Signer: an entity that creates an electronic signature.
 Subsequent Verification: a process performed by a verifier to assess
 the signature validity.
    NOTE: Subsequent verification may be done even years after the
    electronic signature was produced by the signer and completed by
    the initial verification, and it might not need to capture more
    data than those captured at the time of initial verification.
 Time-Stamp Token: a data object that binds a representation of a
 datum to a particular time, thus establishing evidence that the datum
 existed before that time.

Pinkas, et al. Informational [Page 10] RFC 5126 CMS Advanced Electronic Signatures February 2008

 Time-Mark: information in an audit trail from a Trusted Service
 Provider that binds a representation of a datum to a particular time,
 thus establishing evidence that the datum existed before that time.
 Time-Marking Authority: a trusted third party that creates records in
 an audit trail in order to indicate that a datum existed before a
 particular point in time.
 Time-Stamping Authority (TSA): a trusted third party that creates
 time-stamp tokens in order to indicate that a datum existed at a
 particular point in time.
 Time-Stamping Unit (TSU): a set of hardware and software that is
 managed as a unit and has a single time-stamp token signing key
 active at a time.
 Trusted Service Provider (TSP): an entity that helps to build trust
 relationships by making available or providing some information upon
 request.
 Validation Data: additional data that may be used by a verifier of
 electronic signatures to determine that the signature is valid.
 Valid Electronic Signature: an electronic signature that passes
 validation.
 Verifier: an entity that verifies evidence.
    NOTE 1: See ISO/IEC 13888-1 [ISO13888-1].
    NOTE 2: Within the context of the present document, this is an
    entity that validates an electronic signature.

3.2. Abbreviations

 For the purposes of the present document, the following abbreviations
 apply:
 AA           Attribute Authority
 AARL         Attribute Authority Revocation List
 ACRL         Attribute Certificate Revocation List
 API          Application Program Interface
 ASCII        American Standard Code for Information Interchange
 ASN.1        Abstract Syntax Notation 1
 CA           Certification Authority
 CAD          Card Accepting Device
 CAdES        CMS Advanced Electronic Signature
 CAdES-A      CAdES with Archive validation data

Pinkas, et al. Informational [Page 11] RFC 5126 CMS Advanced Electronic Signatures February 2008

 CAdES-BES    CAdES Basic Electronic Signature
 CAdES-C      CAdES with Complete validation data
 CAdES-EPES   CAdES Explicit Policy Electronic Signature
 CAdES-T      CAdES with Time
 CAdES-X      CAdES with eXtended validation data
 CAdES-X Long CAdES with EXtended Long validation data
 CARL         Certification Authority Revocation List
 CMS          Cryptographic Message Syntax
 CRL          Certificate Revocation List
 CWA          CEN (European Committee for Standardization) Workshop
              Agreement
 DER          Distinguished Encoding Rules (for ASN.1)
 DSA          Digital Signature Algorithm
 EDIFACT      Electronic Data Interchange For Administration,
              Commerce and Transport
 EESSI        European Electronic Signature Standardization
              Initiative
 EPES         Explicit Policy-based Electronic Signature
 ES           Electronic Signature
 ESS          Enhanced Security Services (enhances CMS)
 IDL          Interface Definition Language
 MIME         Multipurpose Internet Mail Extensions
 OCSP         Online Certificate Status Provider
 OID          Object IDentifier
 PKC          Public Key Certificate
 PKIX         Public Key Infrastructure using X.509
              (IETF Working Group)
 RSA          Rivest-Shamir-Adleman
 SHA-1        Secure Hash Algorithm 1
 TSA          Time-Stamping Authority
 TSP          Trusted Service Provider
 TST          Time-Stamp Token
 TSU          Time-Stamping Unit
 URI          Uniform Resource Identifier
 URL          Uniform Resource Locator
 XML          Extensible Markup Language
 XMLDSIG      XML Digital Signature

4. Overview

 The present document defines a number of Electronic Signature (ES)
 formats that build on CMS (RFC 3852 [4]) by adding signed and
 unsigned attributes.
 This section:
  1. provides an introduction to the major parties involved

(Section 4.1),

Pinkas, et al. Informational [Page 12] RFC 5126 CMS Advanced Electronic Signatures February 2008

  1. introduces the concept of signature policies (Section 4.2),
  1. provides an overview of the various ES formats (Section 4.3),
  1. introduces the concept of validation data, and provides an

overview of formats that incorporate validation data

      (Section 4.4), and
  1. presents relevant considerations on arbitration

(Section 4.5) and for the validation process (Section 4.6).

 The formal specifications of the attributes are specified in Sections
 5 and 6; Annexes C and D provide rationale for the definitions of the
 different ES forms.

4.1. Major Parties

 The major parties involved in a business transaction supported by
 electronic signatures, as defined in the present document, are:
  1. the signer;
  2. the verifier;
  3. Trusted Service Providers (TSP); and
  4. the arbitrator.
 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, time-stamp tokens,
 CRLs, ARLs, and OCSP responses.  The following TSPs are used to
 support the functions defined in the present document:
  1. Certification Authorities;
  2. Registration Authorities;
  3. CRL Issuers;
  4. OCSP Responders;
  5. Repository Authorities (e.g., a Directory);
  6. Time-Stamping Authorities;
  7. Time-Marking Authorities; and
  8. Signature Policy Issuers.

Pinkas, et al. Informational [Page 13] RFC 5126 CMS Advanced Electronic Signatures February 2008

 Certification Authorities provide users with public key certificates
 and a revocation service.
 Registration Authorities allow the identification and 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.
 Time-Stamping Authorities attest that some data was formed before a
 given trusted time.
 Time-Marking Authorities record that some data was formed before a
 given trusted time.
 Signature Policy Issuers define the signature policies to be used by
 signers and verifiers.
 In some cases, the following additional TSPs are needed:
  1. Attribute Authorities.
 Attributes Authorities provide users with attributes linked to public
 key certificates.
 An Arbitrator is an entity that arbitrates in disputes between a
 signer and a verifier.

4.2. Signature Policies

 The present document includes the concept of signature policies that
 can be used to establish technical consistency when validating
 electronic signatures.
 When a comprehensive signature policy used by the verifier is either
 explicitly indicated by the signer or implied by the data being
 signed, then a consistent result can be obtained when validating an
 electronic signature.
 When the signature policy being used by the verifier is neither
 indicated by the signer nor can be derived from other data, or the
 signature policy is incomplete, then verifiers, including
 arbitrators, may obtain different results when validating an
 electronic signature.  Therefore, comprehensive signature policies
 that ensure consistency of signature validation are recommended from
 both the signer's and verifier's point of view.

Pinkas, et al. Informational [Page 14] RFC 5126 CMS Advanced Electronic Signatures February 2008

 Further information on signature policies is provided in:
  1. TR 102 038 [TR102038];
  2. Sections 5.8.1, C.1, and C.3.1 of the present document;
  3. RFC 3125 [RFC3125]; and
  4. TR 102 272 [TR102272].

4.3. Electronic Signature Formats

 The current section provides an overview for two forms of CMS
 advanced electronic signature specified in the present document,
 namely, the CAdES Basic Electronic Signature (CAdES-BES) and the
 CAdES Explicit Policy-based Electronic Signature (CAdES-EPES).
 Conformance to the present document mandates that the signer create
 one of these formats.

4.3.1. CAdES Basic Electronic Signature (CAdES-BES)

 A CAdES Basic Electronic Signature (CAdES-BES), in accordance with
 the present document, contains:
  1. The signed user data (e.g., the signer's document), as defined

in CMS (RFC 3852 [4]);

  1. A collection of mandatory signed attributes, as defined in CMS

(RFC 3852 [4]) and in ESS (RFC 2634 [5]);

  1. Additional mandatory signed attributes, defined in the present

document; and

  1. The digital signature value computed on the user data and, when

present, on the signed attributes, as defined in CMS (RFC 3852

      [4]).
 A CAdES Basic Electronic Signature (CAdES-BES), in accordance with
 the present document, may contain:
  1. a collection of additional signed attributes; and
  1. a collection of optional unsigned attributes.
 The mandatory signed attributes are:
  1. Content-type. It is defined in RFC 3852 [4] and specifies the

type of the EncapsulatedContentInfo value being signed. Details

      are provided in Section 5.7.1 of the present document.
      Rationale for its inclusion is provided in Annex C.3.7;

Pinkas, et al. Informational [Page 15] RFC 5126 CMS Advanced Electronic Signatures February 2008

  1. Message-digest. It is defined in RFC 3852 [4] and specifies the

message digest of the eContent OCTET STRING within

      encapContentInfo being signed.  Details are provided in Section
      5.7.2;
  1. ESS signing-certificate OR ESS signing-certificate-v2. The ESS

signing-certificate attribute is defined in Enhanced Security

      Services (ESS), RFC 2634 [5], and only allows for the use of
      SHA-1 as a digest algorithm.  The ESS signing-certificate-v2
      attribute is defined in "ESS Update: Adding CertID Algorithm
      Agility", RFC 5035 [15], and allows for the use of any digest
      algorithm.  A CAdES-BES claiming compliance with the present
      document must include one of them.  Section 5.7.3 provides the
      details of these attributes.  Rationale for its inclusion is
      provided in Annex C.3.3.
 Optional signed attributes may be added to the CAdES-BES, including
 optional signed attributes defined in CMS (RFC 3852 [4]), ESS (RFC
 2634 [5]), and the present document.  Listed below are optional
 attributes that are defined in Section 5 and have a rationale
 provided in Annex C:
  1. Signing-time: as defined in CMS (RFC 3852 [4]), indicates the

time of the signature, as claimed by the signer. Details and

      short rationale are provided in Section 5.9.1.  Annex C.3.6
      provides the rationale.
  1. content-hints: as defined in ESS (RFC 2634 [5]), provides

information that describes the innermost signed content of a

      multi-layer message where one content is encapsulated in
      another.  Section 5.10.1 provides the specification details.
      Annex C.3.8 provides the rationale.
  1. content-reference: as defined in ESS (RFC 2634 [5]), can be

incorporated as a way to link request and reply messages in an

      exchange between two parties.  Section 5.10.1 provides the
      specification details.  Annex C.3.9 provides the rationale.
  1. content-identifier: as defined in ESS (RFC 2634 [5]), contains

an identifier that may be used later on in the previous

      content-reference attribute.  Section 5.10.2 provides the
      specification details.
  1. commitment-type-indication: this attribute is defined by the

present document as a way to indicate the commitment endorsed by

      the signer when producing the signature.  Section 5.11.1
      provides the specification details.  Annex C.3.2 provides the
      rationale.

Pinkas, et al. Informational [Page 16] RFC 5126 CMS Advanced Electronic Signatures February 2008

  1. signer-location: this attribute is defined by the present

document. It allows the signer to indicate the place where the

      signer purportedly produced the signature.  Section 5.11.2
      provides the specification details.  Annex C.3.5 provides the
      rationale.
  1. signer-attributes: this attribute is defined by the present

document. It allows a claimed or certified role to be

      incorporated into the signed information.  Section 5.11.3
      provides the specification details.  Annex C.3.4 provides the
      rationale.
  1. content-time-stamp: this attribute is defined by the present

document. It allows a time-stamp token of the data to be signed

      to be incorporated into the signed information.  It provides
      proof of the existence of the data before the signature was
      created.  Section 5.11.4 provides the specification details.
      Annex C.3.6 provides the rationale.
 A CAdES-BES form can also incorporate instances of unsigned
 attributes, as defined in CMS (RFC 3852 [4]) and ESS (RFC 2634 [5]).
  1. CounterSignature, as defined in CMS (RFC 3852 [4]); it can be

incorporated wherever embedded signatures (i.e., a signature on

      a previous signature) are needed.  Section 5.9.2 provides the
      specification details.  Annex C.5 in Annex C provides the
      rationale.
 The structure of the CAdES-BES is illustrated in Figure 1.
              +------Elect.Signature (CAdES-BES)------+
              |+----------------------------------- + |
              ||+---------+ +----------+            | |
              |||Signer's | |  Signed  |  Digital   | |
              |||Document | |Attributes| Signature  | |
              |||         | |          |            | |
              ||+---------+ +----------+            | |
              |+------------------------------------+ |
              +---------------------------------------+
                Figure 1: Illustration of a CAdES-BES
 The signer's conformance requirements of a CAdES-BES are defined in
 Section 8.1.

Pinkas, et al. Informational [Page 17] RFC 5126 CMS Advanced Electronic Signatures February 2008

    NOTE: The CAdES-BES is the minimum format for an electronic
    signature to be generated by the signer.  On its own, it does not
    provide enough information for it to be verified in the longer
    term.  For example, revocation information issued by the relevant
    certificate status information issuer needs to be available for
    long-term validation (see Section 4.4.2).
 The CAdES-BES satisfies the legal requirements for electronic
 signatures, as defined in the European Directive on Electronic
 Signatures, (see Annex C for further discussion on the relationship
 of the present document to the Directive).  It provides basic
 authentication and integrity protection.
 The semantics of the signed data of a CAdES-BES or its context may
 implicitly indicate a signature policy to the verifier.
 Specification of the contents of signature policies is outside the
 scope of the present document.  However, further information on
 signature policies is provided in TR 102 038 [TR102038], RFC 3125
 [RFC3125], and Sections 5.8.1, C.1, and C.3.1 of the present
 document.

4.3.2. CAdES Explicit Policy-based Electronic Signatures (CAdES-EPES)

 A CAdES Explicit Policy-based Electronic Signature (CAdES-EPES), in
 accordance with the present document, extends the definition of an
 electronic signature to conform to the identified signature policy.
 A CAdES Explicit Policy-based Electronic Signature (CAdES-EPES)
 incorporates a signed attribute (sigPolicyID attribute) indicating
 the signature policy that shall be used to validate the electronic
 signature.  This signed attribute is protected by the signature.  The
 signature may also have other signed attributes required to conform
 to the mandated signature policy.
 Section 5.7.3 provides the details on the specification of
 signature-policy-identifier attribute.  Annex C.1 provides a short
 rationale.  Specification of the contents of signature policies is
 outside the scope of the present document.
 Further information on signature policies is provided in TR 102 038
 [TR102038] and Sections 5.8.1, C.1, and C.3.1 of the present
 document.

Pinkas, et al. Informational [Page 18] RFC 5126 CMS Advanced Electronic Signatures February 2008

 The structure of the CAdES-EPES is illustrated in Figure 2.
        +------------- Elect.Signature (CAdES-EPES) ---------------+
        |                                                          |
        |+-------------------------------------------------------+ |
        || +-----------+                                         | |
        || |           |   +---------------------------+         | |
        || |           |   |   +----------+            |         | |
        || | Signer's  |   |   |Signature | Signed     | Digital | |
        || | Document  |   |   |Policy ID | Attributes |Signature| |
        || |           |   |   +----------+            |         | |
        || |           |   +---------------------------+         | |
        || +-----------+                                         | |
        |+-------------------------------------------------------+ |
        |                                                          |
        +----------------------------------------------------------+
                 Figure 2: Illustration of a CAdES-EPES
 The signer's conformance requirements of CAdES-EPES are defined in
 Section 8.2.

4.4. Electronic Signature Formats with Validation Data

 Validation of an electronic signature, in accordance with the present
 document, requires additional data needed to validate the electronic
 signature.  This additional data is called validation data, and
 includes:
  1. Public Key Certificates (PKCs);
  1. revocation status information for each PKC;
  1. trusted time-stamps applied to the digital signature, otherwise

a time-mark shall be available in an audit log.

  1. when appropriate, the details of a signature policy to be used

to verify the electronic signature.

 The validation data may be collected by the signer and/or the
 verifier.  When the signature-policy-identifier signed attribute is
 present, it shall meet the requirements of the signature policy.

Pinkas, et al. Informational [Page 19] RFC 5126 CMS Advanced Electronic Signatures February 2008

 Validation data includes CA certificates as well as revocation status
 information in the form of Certificate Revocation Lists (CRLs) or
 certificate status information (OCSP) provided by an online service.
 Validation data also includes evidence that the signature was created
 before a particular point in time; this may be either a time-stamp
 token or time-mark.
 The present document defines unsigned attributes able to contain
 validation data that can be added to CAdES-BES and CAdES-EPES,
 leading to electronic signature formats that include validation data.
 The sections below summarize these formats and their most relevant
 characteristics.

4.4.1. Electronic Signature with Time (CAdES-T)

 An electronic signature with time (CAdES-T), in accordance with the
 present document, is when there exits trusted time associated with
 the ES.
 The trusted time may be provided by:
  1. a time-stamp attribute as an unsigned attribute added to the ES;

and

  1. a time-mark of the ES provided by a Trusted Service Provider.
 The time-stamp attribute contains a time-stamp token of the
 electronic signature value.  Section 6.1.1 provides the specification
 details.  Annex C.4.3 provides the rationale.
 A time-mark provided by a Trusted Service would have a similar effect
 to the signature-time-stamp attribute, but in this case, no attribute
 is added to the ES, as it is the responsibility of the TSP to provide
 evidence of a time-mark when required to do so.  The management of
 time marks is outside the scope of the present document.
 Trusted time provides the initial steps towards providing long-term
 validity.  Electronic signatures with the time-stamp attribute or a
 time-marked BES/EPES, forming the CAdES-T are illustrated in Figure
 3.

Pinkas, et al. Informational [Page 20] RFC 5126 CMS Advanced Electronic Signatures February 2008

 +-------------------------------------------------CAdES-T ---------+
 |+------ CAdES-BES or CAdES-EPES -------+                          |
 ||+-----------------------------------+ | +----------------------+ |
 |||+---------+ +----------+           | | |                      | |
 ||||Signer's | |  Signed  |  Digital  | | | Signature-time-stamp | |
 ||||Document | |Attributes| Signature | | | attribute required   | |
 ||||         | |          |           | | | when using time      | |
 |||+---------+ +----------+           | | | stamps.              | |
 ||+-----------------------------------+ | |                      | |
 |+--------------------------------------+ | or the BES/EPES      | |
 |                                         | shall be time-marked | |
 |                                         |                      | |
 |                                         | Management and       | |
 |                                         | provision of time    | |
 |                                         | mark is the          | |
 |                                         | responsibility of    | |
 |                                         | the TSP.             | |
 |                                         +----------------------+ |
 +------------------------------------------------------------------+
              Figure 3: Illustration of CAdES-T formats
    NOTE 1: A time-stamp token is added to the CAdES-BES or CAdES-EPES
    as an unsigned attribute.
    NOTE 2: Time-stamp tokens that may themselves include unsigned
    attributes required to validate the time-stamp token, such as the
    complete-certificate-references and complete-revocation-references
    attributes, as defined by the present document.

4.4.2. ES with Complete Validation Data References (CAdES-C)

 Electronic Signature with Complete validation data references
 (CAdES-C), in accordance with the present document, adds to the
 CAdES-T the complete-certificate-references and
 complete-revocation-references attributes, as defined by the present
 document.  The complete-certificate-references attribute contains
 references to all the certificates present in the certification path
 used for verifying the signature.  The complete-revocation-references
 attribute contains references to the CRLs and/or OCSPs responses used
 for verifying the signature.  Section 6.2 provides the specification
 details.  Storing the references allows the values of the
 certification path and the CRLs or OCSPs responses to be stored
 elsewhere, reducing the size of a stored electronic signature format.

Pinkas, et al. Informational [Page 21] RFC 5126 CMS Advanced Electronic Signatures February 2008

 Sections C.4.1 to C.4.2 provide rationale on the usage of validation
 data and when it is suitable to generate the CAdES-C form.
 Electronic signatures, with the additional validation data forming
 the CAdES-C, are illustrated in Figure 4.
 +------------------------- CAdES-C --------------------------------+
 |+----------------------------- CAdES-T ---------+                 |
 ||                                  +----------+ | +-------------+ |
 ||                                  |Timestamp | | |             | |
 ||                                  |attribute | | |             | |
 ||+- CAdES-BES or CAdES-EPES ------+|over      | | |             | |
 |||                                ||digital   | | | Complete    | |
 |||+---------++----------+         ||signature | | | certificate | |
 ||||Signer's ||  Signed  | Digital ||is        | | |     and     | |
 ||||Document ||Attributes|Signature||mandatory | | | revocation  | |
 ||||         ||          |         ||if is not | | | references  | |
 |||+---------++----------+         ||timemarked| | |             | |
 ||+--------------------------------++----------+ | |             | |
 |+-----------------------------------------------+ +-------------+ |
 +------------------------------------------------------------------+
           Figure 4: Illustration of CAdES-C format
    NOTE 1: The complete certificate and revocation references are
    added to the CAdES-T as an unsigned attribute.
    NOTE 2: As a minimum, the signer will provide the CAdES-BES or,
    when indicating that the signature conforms to an explicit signing
    policy, the CAdES-EPES.
    NOTE 3: To reduce the risk of repudiating signature creation, the
    trusted time indication needs to be as close as possible to the
    time the signature was created.  The signer or a TSP could provide
    the CAdES-T; if not, the verifier should create the CAdES-T on
    first receipt of an electronic signature because the CAdES-T
    provides independent evidence of the existence of the signature
    prior to the trusted time indication.
    NOTE 4: A CAdES-T trusted time indication must be created before a
    certificate has been revoked or expired.
    NOTE 5: The signer and TSP could provide the CAdES-C to minimize
    this risk, and when the signer does not provide the CAdES-C, the
    verifier should create the CAdES-C when the required component of
    revocation and validation data become available; this may require
    a grace period.

Pinkas, et al. Informational [Page 22] RFC 5126 CMS Advanced Electronic Signatures February 2008

    NOTE 6: A grace period permits certificate revocation information
    to propagate through the revocation processes.  This period could
    extend from the time an authorized entity requests certificate
    revocation to when the information is available for the relying
    party to use.  In order to make sure that the certificate was not
    revoked at the time the signature was time-marked or time-stamped,
    verifiers should wait until the end of the grace period.  A
    signature policy may define specific values for grace periods.
 An illustration of a grace period is provided in Figure 5.
             +<--------------Grace Period --------->+
 ----+-------+-------+--------+---------------------+----------+
     ^       ^       ^        ^                     ^          ^
     |       |       |        |                     |          |
     |       |       |        |                     |          |
 Signature   |     First      |                   Second       |
  creation   |   revocation   |                  revocation    |
   time      |     status     |                    status      |
             |    checking    |                  checking      |
             |                |                                |
         Time-stamp      Certification                       Build
            or              path                            CAdES-C
         time-mark      construction
           over          & verification
         signature
             Figure 5: Illustration of a grace period
    NOTE 7: CWA 14171 [CWA14171] specifies a signature validation
    process using CAdES-T, CAdES-C, and a grace period.  Annex B
    provides example validation processes.  Annex C.4 provides
    additional information about applying grace periods during the
    validation process.
 The verifier's conformance requirements are defined in Section 8.3
 for time-stamped CAdES-C, and Section 8.4 for time-marked CAdES-C.
 The present document only defines conformance requirements for the
 verifier up to an ES with Complete validation data (CAdES-C).  This
 means that none of the extended and archive forms of electronic
 signatures, as defined in Sections 4.4.3 to 4.4.4, need to be
 implemented to achieve conformance to the present document.

4.4.3. Extended Electronic Signature Formats

 CAdES-C can be extended by adding unsigned attributes to the
 electronic signature.  The present document defines various unsigned
 attributes that are applicable for very long-term verification, and

Pinkas, et al. Informational [Page 23] RFC 5126 CMS Advanced Electronic Signatures February 2008

 for preventing some disaster situations that are discussed in Annex
 C.  Annex B provides the details of the various extended formats, all
 the required unsigned attributes for each type, and how they can be
 used within the electronic signature validation process.  The
 sections below give an overview of the various forms of extended
 signature formats in the present document.

4.4.3.1. EXtended Long Electronic Signature (CAdES-X Long)

 Extended Long format (CAdES-X Long), in accordance with the present
 document, adds the certificate-values and revocation-values
 attributes to the CAdES-C format.  The first one contains the whole
 certificate path required for verifying the signature; the second one
 contains the CRLs and/OCSP responses required for the validation of
 the signature.  This provides a known repository of certificate and
 revocation information required to validate a CAdES-C and prevents
 such information from getting lost.  Sections 6.3.3 and 6.3.4 give
 specification details.  Annex B.1.1 gives details on the production
 of the format.  Annexes C4.1 to C.4.2 provide the rationale.
 The structure of the CAdES-X Long format is illustrated in Figure 6.
 +----------------------- CAdES-X-Long -----------------------------+
 |+------------------------------------ CadES-C --+                 |
 ||                                  +----------+ | +-------------+ |
 ||+------ CAdES -------------------+|Timestamp | | |             | |
 |||                                ||  over    | | | Complete    | |
 |||+---------++----------+         ||digital   | | | certificate | |
 ||||Signer's ||  Signed  | Digital ||signature | | |     and     | |
 ||||Document ||Attributes|Signature||          | | | revocation  | |
 ||||         ||          |         ||Optional  | | |    data     | |
 |||+---------++----------+         ||when      | | |             | |
 ||+--------------------------------+|timemarked| | |             | |
 ||                                  +----------+ | |             | |
 ||                               +-------------+ | +-------------+ |
 ||                               | Complete    | |                 |
 ||                               | certificate | |                 |
 ||                               | and         | |                 |
 ||                               | revocation  | |                 |
 ||                               | references  | |                 |
 ||                               +-------------+ |                 |
 |+-----------------------------------------------+                 |
 |                                                                  |
 +------------------------------------------------------------------+
                Figure 6: Illustration of CAdES-X-Long

Pinkas, et al. Informational [Page 24] RFC 5126 CMS Advanced Electronic Signatures February 2008

4.4.3.2. EXtended Electronic Signature with Time Type 1

        (CAdES-X Type 1)
 Extended format with time type 1 (CAdES-X Type 1), in accordance with
 the present document, adds the CAdES-C-time-stamp attribute, whose
 content is a time-stamp token on the CAdES-C itself, to the CAdES-C
 format.
 This provides an integrity and trusted time protection over all the
 elements and references.  It may protect the certificates, CRLs, and
 OCSP responses in case of a later compromise of a CA key, CRL key, or
 OCSP issuer key.  Section 6.3.5 provides the specification details.
 Annex B.1.2 gives details on the production of the time-stamping
 process.  Annex C.4.4.1 provides the rationale.
 The structure of the CAdES-X Type 1 format is illustrated in Figure
 7.
+----------------------- CAdES-X-Type 1 ------------------------------+
|+-------------------------------------- CAdES-C -----+               |
||                                    +-------------+ | +-----------+ |
||+--------- CAdES ------------------+| Timestamp   | | |           | |
|||                                  || over        | | |           | |
|||+---------++----------+           || digital     | | |           | |
||||Signer's ||  Signed  |  Digital  || signature   | | | Timestamp | |
||||Document ||Attributes| Signature ||             | | |   over    | |
||||         ||          |           || Optional    | | | CAdES-C   | |
|||+---------++----------+           || when        | | |           | |
||+----------------------------------+| time-marked | | |           | |
||                                    +-------------+ | |           | |
||                                    +-------------+ | +-----------+ |
||                                    | Complete    | |               |
||                                    | certificate | |               |
||                                    | and         | |               |
||                                    | revocation  | |               |
||                                    | references  | |               |
||                                    +-------------+ |               |
|+----------------------------------------------------+               |
+---------------------------------------------------------------------+
                Figure 7: Illustration of CAdES-X Type  1

Pinkas, et al. Informational [Page 25] RFC 5126 CMS Advanced Electronic Signatures February 2008

4.4.3.3. EXtended Electronic Signature with Time Type 2

        (CAdES-X Type 2)
 Extended format with time type 2 (CAdES-X Type 2), in accordance with
 the present document, adds to the CAdES-C format the
 CAdES-C-time-stamped-certs-crls-references attribute, whose content
 is a time-stamp token on the certification path and revocation
 information references.  This provides an integrity and trusted time
 protection over all the references.
 It may protect the certificates, CRLs and OCSP responses in case of a
 later compromise of a CA key, CRL key or OCSP issuer key.
 Both CAdES-X Type 1 and CAdES-X Type 2 counter the same threats, and
 the usage of one or the other depends on the environment.  Section
 6.3.5 provides the specification details.  Annex B.1.3 gives details
 on the production of the time-stamping process.  Annex C.4.4.2
 provides the rationale.
 The structure of the CAdES-X Type 2 format is illustrated in Figure
 8.

+————————- CAdES-X-Type 2 —————————-+

+—————————————-CAdES-C —+
+————+
+—– CAdES ———————–+ Timestamp
over
+———+ +———-+ digital +————-+
Signer's Signed Digital signature Time-stamp
Document Attributes signature only over
optional complete
+———+ +———-+ when certificate
+———————————–+ timemarked and
+————+ revocation
+————-+ references
Complete +————-+
certificate
and
revocation
references
+————-+
+—————————————————+

+———————————————————————+

                Figure 8: Illustration of CAdES-X Type 2

Pinkas, et al. Informational [Page 26] RFC 5126 CMS Advanced Electronic Signatures February 2008

4.4.3.4. EXtended Long Electronic Signature with Time (CAdES-X Long

        Type 1 or 2)
 Extended Long with Time (CAdES-X Long Type 1 or 2), in accordance
 with the present document, is a combination of CAdES-X Long and one
 of the two former types (CAdES-X Type 1 and CAdES-X Type 2).  Annex
 B.1.4 gives details on the production of the time-stamping process.
 Annex C.4.8 in Annex C provides the rationale.
 The structure of the CAdES-X Long Type 1 and CAdES-X Long Type 2
 format is illustrated in Figure 9.
 +------------------ CAdES-X Long Type 1 or 2 -----------------------+
 |                                                   +--------------+|
 |+-------------------------------------- CAdES-C --+|+------------+||
 ||                                                 ||| Timestamp  |||
 ||+------- CAdES --------------------++----------+ |||   over     |||
 |||                                  ||Timestamp | |||  CAdES-C   |||
 |||                                  ||over      | ||+------------+||
 |||+---------++----------+           ||digital   | ||      OR      ||
 ||||Signer's ||  Signed  | Digital   ||signature | ||+------------+||
 ||||Document ||Attributes| signature ||          | ||| Timestamp  |||
 ||||         ||          |           ||Optional  | ||| only over  |||
 |||+---------++----------+           ||when      | ||| complete   |||
 ||+----------------------------------+|timemarked| ||| certificate|||
 ||                                    +----------+ |||    and     |||
 ||                                                 ||| Revocation |||
 ||                                 +-------------+ ||| References |||
 ||                                 | Complete    | ||+------------+||
 ||                                 | certificate | |+--------------+|
 ||                                 | and         | | +------------+ |
 ||                                 | revocation  | | | Complete   | |
 ||                                 | references  | | |certificate | |
 ||                                 +-------------+ | |   and      | |
 |+-------------------------------------------------+ |revocation  | |
 |                                                    |  value     | |
 |                                                    +------------+ |
 +-------------------------------------------------------------------+
   Figure 9: Illustration of CAdES-X Long Type 1 and CAdES Long Type 2

4.4.4. Archival Electronic Signature (CAdES-A)

 Archival Form (CAdES-A), in accordance with the present document,
 builds on a CAdES-X Long or a CAdES-X Long Type 1 or 2 by adding one
 or more archive-time-stamp attributes.  This form is used for
 archival of long-term signatures.  Successive time-stamps protect the
 whole material against vulnerable hashing algorithms or the breaking

Pinkas, et al. Informational [Page 27] RFC 5126 CMS Advanced Electronic Signatures February 2008

 of the cryptographic material or algorithms.  Section 6.4 contains
 the specification details.  Sections C.4.5 and C.4.8 provide the
 rationale.
 The structure of the CAdES-A form is illustrated in Figure 10.
+---------------------------CAdES-A ---------------------------------+
|+----------------------------------------------------+              |
||                                    +--------------+| +----------+ |
||+----------------------CAdES-C ----+|+------------+|| |          | |
|||                     +----------+ ||| Timestamp  ||| |          | |
|||+---- CAdES-BES ----+|Timestamp | |||    over    ||| |          | |
||||    or CAdeS-EPES  ||  over    | |||   CAdES-C  ||| |  Archive | |
||||                   ||digital   | ||+------------+|| |          | |
||||                   ||signature | ||      or      || |Timestamp | |
||||                   ||          | ||+------------+|| |          | |
||||                   ||Optional  | ||| Timestamp  ||| |          | |
||||                   ||when      | ||| only over  ||| |          | |
||||                   ||Timemarked| ||| complete   ||| |          | |
|||+-------------------+|          | ||| certificate||| +----------+ |
|||                     +----------+ |||    and     |||              |
|||                  +-------------+ ||| revocation |||              |
|||                  | Complete    | ||| references |||              |
|||                  | certificate | ||+------------+||              |
|||                  | and         | |+--------------+|              |
|||                  | revocation  | | +------------+ |              |
|||                  | references  | | |  Complete  | |              |
|||                  +-------------+ | |certificate | |              |
|||                                  | |    and     | |              |
||+----------------------------------+ |revocation  | |              |
||                                     |  values    | |              |
||                                     +------------+ |              |
|+----------------------------------------------------+              |
+--------------------------------------------------------------------+
                   Figure 10: Illustration of CAdES-A

4.5. Arbitration

 The CAdES-C may be used for arbitration should there be a dispute
 between the signer and verifier, provided that:
  1. the arbitrator knows where to retrieve the signer's certificate

(if not already present), all the cross-certificates and the

      required CRLs, ACRLs, or OCSP responses referenced in the
      CAdES-C;

Pinkas, et al. Informational [Page 28] RFC 5126 CMS Advanced Electronic Signatures February 2008

  1. when time-stamping in the CAdES-T is being used, the certificate

from the TSU that has issued the time-stamp token in the CAdES-T

      format is still within its validity period;
  1. when time-stamping in the CAdES-T is being used, the certificate

from the TSU that has issued the time-stamp token in the CAdES-T

      format is not revoked at the time of arbitration;
  1. when time-marking in the CAdES-T is being used, a reliable audit

trail from the Time-Marking Authority is available for

      examination regarding the time;
  1. none of the private keys corresponding to the certificates used

to verify the signature chain have ever been compromised;

  1. the cryptography used at the time the CAdES-C was built has not

been broken at the time the arbitration is performed; and

  1. if the signature policy can be explicitly or implicitly

identified, then an arbitrator is able to determine the rules

      required to validate the electronic signature.

4.6. Validation Process

 The validation process validates an electronic signature; the output
 status of the validation process can be:
  1. invalid;
  1. incomplete validation; or
  1. valid.
 An invalid response indicates that either the signature format is
 incorrect or that the digital signature value fails verification
 (e.g., the integrity check 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 signature
 validation status is currently unknown.  In the case of incomplete
 validation, additional information may be made available to the
 application or user, thus allowing them to decide what to do with the
 electronic signature.  In the case of incomplete validation, the
 electronic signature may be checked again at some later time when
 additional information becomes available.

Pinkas, et al. Informational [Page 29] RFC 5126 CMS Advanced Electronic Signatures February 2008

    NOTE: For example, an incomplete validation may be because all the
    required certificates are not available or the grace period is not
    completed.
 A valid response indicates that the signature has passed
 verification, and it complies with the signature validation policy.
 Example validation sequences are illustrated in Annex B.

5. Electronic Signature Attributes

 This section builds upon the existing Cryptographic Message Syntax
 (CMS), as defined in RFC 3852 [4], and Enhanced Security Services
 (ESS), as defined in RFC 2634 [5].  The overall structure of an
 Electronic Signature is as defined in CMS.  The Electronic Signature
 (ES) uses attributes defined in CMS, ESS, and the present document.
 The present document defines ES attributes that it uses and that are
 not defined elsewhere.
 The mandated set of attributes and the digital signature value is
 defined as the minimum Electronic Signature (ES) required by the
 present document.  A signature policy may mandate that other signed
 attributes be present.

5.1. General Syntax

 The general syntax of the ES is as defined in CMS (RFC 3852 [4]).
    NOTE: CMS defines content types for id-data, id-signedData,
    id-envelopedData, id-digestedData, id-encryptedData, and
    id-authenticatedData.  Although CMS permits other documents to
    define other content types, the ASN.1 type defined should not be a
    CHOICE type.  The present document does not define other content
    types.

5.2. Data Content Type

 The data content type of the ES is as defined in CMS (RFC 3852 [4]).
    NOTE: If the content type is id-data, it is recommended that the
    content be encoded using MIME, and that the MIME type is used to
    identify the presentation format of the data.  See Annex F.1 for
    an example of using MIME to identify the encoding type.

5.3. Signed-data Content Type

 The Signed-data content type of the ES is as defined in CMS (RFC 3852
 [4]).

Pinkas, et al. Informational [Page 30] RFC 5126 CMS Advanced Electronic Signatures February 2008

5.4. SignedData Type

 The syntax of the SignedData of the ES is as defined in CMS (RFC 3852
 [4]).
 The fields of type SignedData are as defined in CMS (RFC 3852 [4]).
 The identification of a signer's certificate used to create the
 signature is always signed (see Section 5.7.3).  The validation
 policy may specify requirements for the presence of certain
 certificates.  The degenerate case, where there are no signers, is
 not valid in the present document.

5.5. EncapsulatedContentInfo Type

 The syntax of the EncapsulatedContentInfo type ES is as defined in
 CMS (RFC 3852 [4]).
 For the purpose of long-term validation, as defined by the present
 document, it is advisable that either the eContent is present, or the
 data that is signed is archived in such as way as to preserve 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.
    NOTE: The eContent is optional in CMS :
  1. When it is present, this allows the signed data to be

encapsulated in the SignedData structure, which then

          contains both the signed data and the signature.  However,
          the signed data may only be accessed by a verifier able to
          decode the ASN.1 encoded SignedData structure.
  1. When it is missing, this allows the signed data to be sent

or stored separately from the signature, and the SignedData

          structure only contains the signature.  It is, in the case
          of the signature, only the data that is signed that needs to
          be stored and distributed in such as way as to preserve any
          data encoding.
 The degenerate case where there are no signers is not valid in the
 present document.

5.6. SignerInfo Type

 The syntax of the SignerInfo type ES is as defined in CMS (RFC 3852
 [4]).

Pinkas, et al. Informational [Page 31] RFC 5126 CMS Advanced Electronic Signatures February 2008

 Per-signer information is represented in the type SignerInfo.  In the
 case of multiple independent signatures (see Annex B.5), there is an
 instance of this field for each signer.
 The fields of type SignerInfo have the meanings defined in CMS (RFC
 3852 [4]), but the signedAttrs field shall contain the following
 attributes:
  1. content-type, as defined in Section 5.7.1; and
  1. message-digest, as defined in Section 5.7.2;
  1. signing-certificate, as defined in Section 5.7.3.

5.6.1. Message Digest Calculation Process

 The message digest calculation process is as defined in CMS (RFC 3852
 [4]).

5.6.2. Message Signature Generation Process

 The input to the message signature generation process is as defined
 in CMS (RFC 3852 [4]).

5.6.3. Message Signature Verification Process

 The procedures for message signature verification are defined in CMS
 (RFC 3852 [4]) and enhanced in the present document: the input to the
 signature verification process must be the signer's public key, which
 shall be verified as correct using the signing certificate reference
 attribute containing a reference to the signing certificate, i.e.,
 when SigningCertificateV2 from RFC 5035 [16] or SigningCertificate
 from ESS [5] is used, the public key from the first certificate
 identified in the sequence of certificate identifiers from
 SigningCertificate must be the key used to verify the digital
 signature.

5.7. Basic ES Mandatory Present Attributes

 The following attributes shall be present with the signed-data
 defined by the present document.  The attributes are defined in CMS
 (RFC 3852 [4]).

5.7.1. content-type

 The content-type attribute indicates the type of the signed content.
 The syntax of the content-type attribute type is as defined in CMS
 (RFC 3852 [4]) Section 11.1.

Pinkas, et al. Informational [Page 32] RFC 5126 CMS Advanced Electronic Signatures February 2008

    NOTE 1: As stated in RFC 3852 [4] , the content-type attribute
    must have its value (i.e., ContentType) equal to the eContentType
    of the EncapsulatedContentInfo value being signed.
    NOTE 2: For implementations supporting signature generation, if
    the content-type attribute is id-data, then it is recommended that
    the eContent be encoded using MIME.  For implementations
    supporting signature verification, if the signed data (i.e.,
    eContent) is MIME-encoded, then the OID of the content-type
    attribute must be id-data.  In both cases, the MIME
    content-type(s) must be used to identify the presentation format
    of the data.  See Annex F for further details about the use of
    MIME.

5.7.2. Message Digest

 The syntax of the message-digest attribute type of the ES is as
 defined in CMS (RFC 3852 [4]).

5.7.3. Signing Certificate Reference Attributes

 The Signing certificate reference attributes are supported by using
 either the ESS signing-certificate attribute or the
 ESS-signing-certificate-v2 attribute.
 These attributes shall contain a reference to the signer's
 certificate; they are designed to prevent simple substitution and
 reissue attacks and to allow for a restricted set of certificates to
 be used in verifying a signature.  They have a compact form (much
 shorter than the full certificate) that allows for a certificate to
 be unambiguously identified.
 One, and only one, of the following alternative attributes shall be
 present with the signedData, defined by the present document:
  1. The ESS signing-certificate attribute, defined in ESS [5], must

be used if the SHA-1 hashing algorithm is used.

  1. The ESS signing-certificate-v2 attribute, defined in "ESS

Update: Adding CertID Algorithm Agility", RFC 5035 [15], which

      shall be used when other hashing algorithms are to be used.
 The certificate to be used to verify the signature shall be
 identified in the sequence (i.e., the certificate from the signer),
 and the sequence shall not be empty.  The signature validation policy
 may mandate other certificates be present that may include all the
 certificates up to the trust anchor.

Pinkas, et al. Informational [Page 33] RFC 5126 CMS Advanced Electronic Signatures February 2008

5.7.3.1. ESS signing-certificate Attribute Definition

 The syntax of the signing-certificate attribute type of the ES is as
 defined in Enhanced Security Services (ESS), RFC 2634 [5], and
 further qualified in the present document.
 The sequence of the policy information field is not used in the
 present document.
 The ESS signing-certificate attribute shall be a signed attribute.
 The encoding of the ESSCertID for this certificate shall include the
 issuerSerial field.
 If present, the issuerAndSerialNumber in SignerIdentifier field of
 the SignerInfo shall match the issuerSerial field present in
 ESSCertID.  In addition, the certHash from ESSCertID shall match the
 SHA-1 hash of the certificate.  The certificate identified shall 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 shall be considered invalid.
    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-attributes
    attribute as defined in Section 5.8.3.

5.7.3.2. ESS signing-certificate-v2 Attribute Definition

 The ESS signing-certificate-v2 attribute is similar to the ESS
 signing-certificate defined above, except that this attribute can be
 used with hashing algorithms other than SHA-1.
 The syntax of the signing-certificate-v2 attribute type of the ES is
 as defined in "ESS Update: Adding CertID Algorithm Agility", RFC 5035
 [15], and further qualified in the present document.
 The sequence of the policy information field is not used in the
 present document.
 This attribute shall be used in the same manner as defined above for
 the ESS signing-certificate attribute.
 The object identifier for this attribute is:
       id-aa-signingCertificateV2 OBJECT IDENTIFIER ::=
       { iso(1) member-body(2) us(840) rsadsi(113549) pkcs(1) pkcs9(9)
         smime(16) id-aa(2) 47 }

Pinkas, et al. Informational [Page 34] RFC 5126 CMS Advanced Electronic Signatures February 2008

 If present, the issuerAndSerialNumber in SignerIdentifier field of
 the SignerInfo shall match the issuerSerial field present in
 ESSCertIDv2.  In addition, the certHash from ESSCertIDv2 shall match
 the hash of the certificate computed using the hash function
 specified in the hashAlgorithm field.  The certificate identified
 shall 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 shall be considered invalid.
    NOTE 1: 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-attributes
    attribute as defined in Section 5.8.3.
    NOTE 2: RFC 3126 was using the other signing-certificate attribute
    (see Section 5.7.3.3) for the same purpose.  Its use is now
    deprecated, since this structure is simpler.

5.7.3.3. Other signing-certificate Attribute Definition

 RFC 3126 was using the other signing-certificate attribute as an
 alternative to the ESS signing-certificate when hashing algorithms
 other than SHA-1 were being used.  Its use is now deprecated, since
 the structure of the signing-certificate-v2 attribute is simpler.
 Its description is however still present in this version for
 backwards compatibility.
 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 other-signing-certificate attribute value has the ASN.1 syntax
 OtherSigningCertificate:
 OtherSigningCertificate ::=  SEQUENCE {
     certs        SEQUENCE OF OtherCertID,
     policies     SEQUENCE OF PolicyInformation OPTIONAL
                  -- NOT USED IN THE PRESENT DOCUMENT }
 OtherCertID ::= SEQUENCE {
     otherCertHash            OtherHash,
     issuerSerial             IssuerSerial OPTIONAL }
 OtherHash ::= CHOICE {
     sha1Hash OtherHashValue,  -- This contains a SHA-1 hash
     otherHash OtherHashAlgAndValue}
 OtherHashValue ::= OCTET STRING

Pinkas, et al. Informational [Page 35] RFC 5126 CMS Advanced Electronic Signatures February 2008

 OtherHashAlgAndValue ::= SEQUENCE {
     hashAlgorithm     AlgorithmIdentifier,
     hashValue         OtherHashValue }

5.8. Additional Mandatory Attributes for Explicit Policy-based

    Electronic Signatures

5.8.1. signature-policy-identifier

 The present document mandates that for CAdES-EPES, a reference to the
 signature policy is included in the signedData.  This reference is
 explicitly identified.  A signature policy defines the rules for
 creation and validation of an electronic signature, and is included
 as a signed attribute with every Explicit Policy-based Electronic
 Signature.  The signature-policy-identifier shall 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 ::= CHOICE {
         signaturePolicyId          SignaturePolicyId,
         signaturePolicyImplied     SignaturePolicyImplied
                                    -- not used in this version
 }
    SignaturePolicyId ::= SEQUENCE {
         sigPolicyId           SigPolicyId,
         sigPolicyHash         SigPolicyHash,
         sigPolicyQualifiers   SEQUENCE SIZE (1..MAX) OF
                                 SigPolicyQualifierInfo OPTIONAL}
    SignaturePolicyImplied ::= NULL

Pinkas, et al. Informational [Page 36] RFC 5126 CMS Advanced Electronic Signatures February 2008

 The sigPolicyId field contains an object-identifier that uniquely
 identifies a specific version of the signature policy.  The syntax of
 this field is as follows:
    SigPolicyId ::= OBJECT IDENTIFIER
 The sigPolicyHash field optionally contains the identifier of the
 hash algorithm and the hash of the value of the signature policy.
 The hashValue within the sigPolicyHash may be set to zero to indicate
 that the policy hash value is not known.
    NOTE: The use of a zero sigPolicyHash value is to ensure backwards
    compatibility with earlier versions of the current document.  If
    sigPolicyHash is zero, then the hash value should not be checked
    against the calculated hash value of the signature policy.
 If the signature policy is defined using ASN.1, then the hash is
 calculated on the value without the outer type and length fields, and
 the hashing algorithm shall be as specified in the field
 sigPolicyHash.
 If the signature policy is defined using another structure, the type
 of structure and the hashing algorithm shall be either specified as
 part of the signature policy, or indicated using a signature policy
 qualifier.
    SigPolicyHash ::= OtherHashAlgAndValue
    OtherHashAlgAndValue ::= SEQUENCE {
       hashAlgorithm   AlgorithmIdentifier,
       hashValue       OtherHashValue }
    OtherHashValue ::= OCTET STRING
 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 }

Pinkas, et al. Informational [Page 37] RFC 5126 CMS Advanced Electronic Signatures February 2008

 The present document specifies the following qualifiers:
  1. spuri: this contains the web URI or URL reference to the

signature policy, and

  1. sp-user-notice: this contains a user notice that should be

displayed whenever the signature is validated.

         sigpolicyQualifierIds defined in the present 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)) }

5.9. CMS Imported Optional Attributes

 The following attributes may be present with the signed-data; the
 attributes are defined in CMS (RFC 3852 [4]) and are imported into
 the present document.  Where appropriate, the attributes are
 qualified and profiled by the present document.

5.9.1. signing-time

 The signing-time attribute specifies the time at which the signer
 claims to have performed the signing process.

Pinkas, et al. Informational [Page 38] RFC 5126 CMS Advanced Electronic Signatures February 2008

 Signing-time attribute values for ES have the ASN.1 type SigningTime
 as defined in CMS (RFC 3852 [4]).
    NOTE: RFC 3852 [4] states that dates between January 1, 1950 and
    December 31, 2049 (inclusive) must be encoded as UTCTime.  Any
    dates with year values before 1950 or after 2049 must be encoded
    as GeneralizedTime.

5.9.2. countersignature

 The countersignature attribute values for ES have ASN.1 type
 CounterSignature, as defined in CMS (RFC 3852 [4]).  A
 countersignature attribute shall be an unsigned attribute.

5.10. ESS-Imported Optional Attributes

 The following attributes may be present with the signed-data defined
 by the present document.  The attributes are defined in ESS and are
 imported into the present document and are appropriately qualified
 and profiled by the present document.

5.10.1. 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 shall be a signed
 attribute.
 content-reference attribute values for ES have ASN.1 type
 ContentReference, as defined in ESS (RFC 2634 [5]).
 The content-reference attribute shall be used as defined in ESS (RFC
 2634 [5]).

5.10.2. content-identifier Attribute

 The content-identifier attribute provides an identifier for the
 signed content, for use when a reference may be later required to
 that content; for example, in the content-reference attribute in
 other signed data sent later.  The content-identifier shall be a
 signed attribute.
 content-identifier attribute type values for the ES have an ASN.1
 type ContentIdentifier, as defined in ESS (RFC 2634 [5]).
 The minimal content-identifier attribute should contain a
 concatenation of user-specific identification information (such as a

Pinkas, et al. Informational [Page 39] RFC 5126 CMS Advanced Electronic Signatures February 2008

 user name or public keying material identification information), a
 GeneralizedTime string, and a random number.

5.10.3. content-hints Attribute

 The content-hints attribute provides information on the innermost
 signed content of a multi-layer message where one content is
 encapsulated in another.
 The syntax of the content-hints attribute type of the ES is as
 defined in ESS (RFC 2634 [5]).
 When used to indicate the precise format of the data to be presented
 to the user, the following rules apply:
  1. the contentType indicates the type of the associated content.

It is an object identifier (i.e., a unique string of integers)

      assigned by an authority that defines the content type; and
  1. when the contentType is id-data, the contentDescription shall

define the presentation format; the format may be defined by

      MIME types.
 When the format of the content is defined by MIME types, the
 following rules apply:
  1. the contentType shall be id-data, as defined in CMS (RFC 3852

[4]);

  1. the contentDescription shall be used to indicate the encoding of

the data, in accordance with the rules defined RFC 2045 [6]; see

      Annex F for an example of structured contents and MIME.
 NOTE 1: id-data OBJECT IDENTIFIER ::= { iso(1) member-body(2) us(840)
 rsadsi(113549) pkcs(1) pkcs7(7) 1 }
 NOTE 2: contentDescription is optional in ESS (RFC 2634 [5]).  It may
 be used to complement contentTypes defined elsewhere; such
 definitions are outside the scope of the present document.

5.11. Additional Optional Attributes Defined in the Present Document

 This section defines a number of attributes that may be used to
 indicate additional information to a verifier:
    a) the type of commitment from the signer, and/or
    b) the claimed location where the signature is performed, and/or

Pinkas, et al. Informational [Page 40] RFC 5126 CMS Advanced Electronic Signatures February 2008

    c) claimed attributes or certified attributes of the signer,
       and/or
    d) a content time-stamp applied before the content was signed.

5.11.1. commitment-type-indication Attribute

 There may be situations where 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 commitment-type-indication
 attribute conveys such information.
 The commitment-type-indication attribute shall be a signed attribute.
 The commitment type may be:
  1. defined as part of the signature policy, in which case, the

commitment type has precise semantics that are defined as part

      of the signature policy; and
  1. 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

Pinkas, et al. Informational [Page 41] RFC 5126 CMS Advanced Electronic Signatures February 2008

CommitmentTypeQualifier ::= SEQUENCE {

 commitmentTypeIdentifier   CommitmentTypeIdentifier,
 qualifier                  ANY DEFINED BY commitmentTypeIdentifier }
 The use of any qualifiers to the commitment type is outside the scope
 of the present document.
 The following generic commitment types are defined in the present
 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 meanings:
 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.

Pinkas, et al. Informational [Page 42] RFC 5126 CMS Advanced Electronic Signatures February 2008

 Proof of creation indicates that the signer has created the message
 (but not necessarily approved, nor sent it).

5.11.2. signer-location Attribute

 The signer-location attribute 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 [11]).
 The signer-location attribute shall 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 {

  1. - at least one of the following shall be present:

countryName [0] DirectoryString OPTIONAL,

  1. - As used to name a Country in X.500

localityName [1] DirectoryString OPTIONAL,

  1. - As used to name a locality in X.500

postalAdddress [2] PostalAddress OPTIONAL }

PostalAddress ::= SEQUENCE SIZE(1..6) OF DirectoryString

5.11.3. signer-attributes Attribute

 The signer-attributes attribute specifies additional attributes of
 the signer (e.g., role).  It may be either:
  1. claimed attributes of the signer; or
  1. certified attributes of the signer.
 The signer-attributes attribute shall 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}

Pinkas, et al. Informational [Page 43] RFC 5126 CMS Advanced Electronic Signatures February 2008

 signer-attributes values have ASN.1 type SignerAttribute:
 SignerAttribute ::= SEQUENCE OF CHOICE {
     claimedAttributes     [0]   ClaimedAttributes,
     certifiedAttributes   [1]   CertifiedAttributes }
 ClaimedAttributes ::= SEQUENCE OF Attribute
 CertifiedAttributes ::= AttributeCertificate
 -- as defined in RFC 3281: see Section 4.1.
    NOTE 1: Only a single signer-attributes can be used.
    NOTE 2: Attribute and AttributeCertificate are as defined
    respectively in ITU-T Recommendations X.501 [9] and X.509 [1].

5.11.4. content-time-stamp Attribute

 The content-time-stamp attribute is an attribute that is the
 time-stamp token of the signed data content before it is signed.  The
 content-time-stamp attribute shall be a signed attribute.
 The following object identifier identifies the content-time-stamp
 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-time-stamp attribute values have ASN.1 type ContentTimestamp:
 ContentTimestamp ::= TimeStampToken
 The value of messageImprint of TimeStampToken (as described in RFC
 3161 [7]) shall be a hash of the value of the eContent field within
 encapContentInfo in the signedData.
 For further information and definition of TimeStampToken, see Section
 7.4.
    NOTE: content-time-stamp indicates that the signed information was
    formed before the date included in the content-time-stamp.

5.12. Support for Multiple Signatures

5.12.1. Independent Signatures

 Multiple independent signatures (see Annex B.5) are supported by
 independent SignerInfo from each signer.

Pinkas, et al. Informational [Page 44] RFC 5126 CMS Advanced Electronic Signatures February 2008

 Each SignerInfo shall include all the attributes required under the
 present document and shall be processed independently by the
 verifier.
    NOTE: Independent signatures may be used to provide independent
    signatures from different parties with different signed
    attributes, or to provide multiple signatures from the same party
    using alternative signature algorithms, in which case the other
    attributes, excluding time values and signature policy
    information, will generally be the same.

5.12.2. Embedded Signatures

 Multiple embedded signatures (see Annex C.5) are supported using the
 countersignature unsigned attribute (see Section 5.9.2).  Each
 counter signature is carried in countersignature held as an unsigned
 attribute to the SignerInfo to which the counter-signature is
 applied.
    NOTE: Counter signatures may be used to provide signatures from
    different parties with different signed attributes, or to provide
    multiple signatures from the same party using alternative
    signature algorithms, in which case the other attributes,
    excluding time values and signature policy information, will
    generally be the same.

6. Additional Electronic Signature Validation Attributes

 This section specifies attributes that contain different types of
 validation data.  These attributes build on the electronic signature
 specified in Section 5.  This includes:
  1. Signature-time-stamp applied to the electronic signature value

or a Time-Mark in an audit trail. This is defined as the

      Electronic Signature with Time (CAdES-T); and
  1. Complete validation data references that comprise the time-stamp

of the signature value, plus references to all the certificates

      (complete-certificate-references) and revocation (complete-
      revocation-references) information used for full validation of
      the electronic signature.  This is defined as the Electronic
      Signature with Complete data references (CAdES-C).
    NOTE 1: Formats for CAdES-T are illustrated in Section 4.4, and
    the attributes are defined in Section 6.1.1.

Pinkas, et al. Informational [Page 45] RFC 5126 CMS Advanced Electronic Signatures February 2008

    NOTE 2: Formats for CAdES-C are illustrated in Section 4.4.  The
    required attributes for the CAdES-C signature format are defined
    in Sections 6.2.1 to 6.2.2; optional attributes are defined in
    Sections 6.2.3 and 6.2.4.
 In addition, the following optional extended forms of validation data
 are also defined; see Annex B for an overview of the extended forms
 of validation data:
  1. CAdES-X with time-stamp: there are two types of time-stamps used

in extended validation data defined by the present document;

  1. Type 1(CAdES-X Type 1): comprises a time-stamp over the ES

with Complete validation data (CAdES-C); and

  1. Type 2 (CAdES-X Type2): comprises a time-stamp over the

certification path references and the revocation information

         references used to support the CAdES-C.
    NOTE 3: Formats for CAdES-X Type 1 and CAdES-X Type 2 are
    illustrated in Sections B.1.2 and B.1.3, respectively.
  1. CAdES-X Long: comprises the Complete validation data

references (CAdES-C), plus the actual values of all the

         certificates and revocation information used in the CAdES-C.
    NOTE 4: Formats for CAdES-X Long are illustrated in Annex B.1.1.
  1. CAdES-X Long Type 1 or CAdES-X Long Type 2: comprises an

X-Time-Stamp (Type 1 or Type 2), plus the actual values of

         all the certificates and revocation information used in the
         CAdES-C as per CAdES-X Long.
 This section also specifies the data structures used in Archive
 validation data format (CAdES-A)of extended forms:
  1. Archive form of electronic signature (CAdES-A) comprises:
  1. the Complete validation data references (CAdES-C),
  1. the certificate and revocation values (as in a CAdES-X Long ),
  1. any existing extended electronic signature time-stamps

(CAdES-X Type 1 or CAdES-X Type 2), if present, and

  1. the signed user data and an additional archive time-stamp

applied over all that data.

Pinkas, et al. Informational [Page 46] RFC 5126 CMS Advanced Electronic Signatures February 2008

      An archive time-stamp may be repeatedly applied after long
      periods to maintain validity when electronic signature and
      time-stamping 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.  Thus, all the attributes defined
 in Section 6 are unsigned attributes.
    NOTE 5: Where multiple signatures are to be supported, as
    described in Section 5.12, each signature has a separate
    SignerInfo.  Thus, each signature requires its own unsigned
    attribute values to create CAdES-T, CAdES-C, etc.
    NOTE 6: The optional attributes of the extended validation data
    are defined in Sections 6.3 and 6.4.

6.1. signature time-stamp Attribute (CAdES-T)

 An electronic signature with time-stamp 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 are available, but not all).
 The minimum structure time-stamp validation data is:
  1. the signature time-stamp attribute, as defined in Section 6.1.1,

over the ES signature value.

6.1.1. signature-time-stamp Attribute Definition

 The signature-time-stamp attribute is a TimeStampToken computed on
 the signature value for a specific signer; it is an unsigned
 attribute.  Several instances of this attribute may occur with an
 electronic signature, from different TSAs.
 The following object identifier identifies the signature-time-stamp
 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-time-stamp attribute value has ASN.1 type
 SignatureTimeStampToken:
 SignatureTimeStampToken ::= TimeStampToken

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 The value of the messageImprint field within TimeStampToken shall be
 a hash of the value of the signature field within SignerInfo for the
 signedData being time-stamped.
 For further information and definition of TimeStampToken, see Section
 7.4.
    NOTE 1: In the case of multiple signatures, it is possible to have
    a:
  1. TimeStampToken computed for each and all signers; or
  1. TimeStampToken computed on one signer's signature; and no
  1. TimeStampToken on another signer's signature.
    NOTE 2: In the case of multiple signatures, several TSTs, issued
    by different TSAs, may be present within the same signerInfo (see
    RFC 3852 [4]).

6.2. Complete Validation Data References (CAdES-C)

 An electronic signature with Complete validation data references
 (CAdES-C) is an electronic signature for which all the additional
 data required for validation (i.e., all certificates and revocation
 information) is available.  This form is built on the CAdES-T form
 defined above.
 As a minimum, the Complete validation data shall include the
 following:
  1. a time, which shall either be a signature-timestamp attribute,

as defined in Section 6.1.1, or a time-mark operated by a

      Time-Marking Authority;
  1. complete-certificate-references, as defined in Section 6.2.1;
  1. complete-revocation-references, as defined in Section 6.2.2.

6.2.1. complete-certificate-references Attribute Definition

 The complete-certificate-references attribute is an unsigned
 attribute.  It references the full set of CA certificates that have
 been used to validate an ES with Complete validation data up to (but
 not including) the signer's certificate.  Only a single instance of
 this attribute shall occur with an electronic signature.

Pinkas, et al. Informational [Page 48] RFC 5126 CMS Advanced Electronic Signatures February 2008

    NOTE 1: The signer's certificate is referenced in the signing
    certificate attribute (see Section 5.7.3).

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-references attribute value has the ASN.1
 syntax CompleteCertificateRefs.
 CompleteCertificateRefs ::=  SEQUENCE OF OtherCertID
 OtherCertID is defined in Section 5.7.3.3.
 The IssuerSerial that shall be present in OtherCertID.  The certHash
 shall match the hash of the certificate referenced.
    NOTE 2: Copies of the certificate values may be held using the
    certificate-values attribute, defined in Section 6.3.3.
    This attribute may include references to the certification chain
    for any TSUs that provides time-stamp tokens.  In this case, the
    unsigned attribute shall be added to the signedData of the
    relevant time-stamp token as an unsignedAttrs in the signerInfos
    field.

6.2.2. complete-revocation-references Attribute Definition

 The complete-revocation-references attribute is an unsigned
 attribute.  Only a single instance of this attribute shall occur with
 an electronic signature.  It references the full set of the CRL,
 ACRL, or OCSP responses that have been used in the validation of the
 signer, and CA certificates used in ES with Complete validation data.
 This attribute indicates that the verifier has taken due diligence to
 gather the available revocation information.  The references stored
 in this attribute can be used to retrieve the referenced information,
 if not stored in the CMS structure, but somewhere else.
 The following object identifier identifies the
 complete-revocation-references 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}

Pinkas, et al. Informational [Page 49] RFC 5126 CMS Advanced Electronic Signatures February 2008

 The complete-revocation-references 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
 }
 CompleteRevocationRefs shall contain one CrlOcspRef for the
 signing-certificate, followed by one for each OtherCertID in the
 CompleteCertificateRefs attribute.  The second and subsequent
 CrlOcspRef fields shall be in the same order as the OtherCertID 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                   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

}

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 When creating a 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 shall correspond to the time thisUpdate
 contained in the issued CRL, and if present, the crlNumber.  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 shall be included.
 The OcspIdentifier is to identify the OCSP response using the issuer
 name and the time of issue of the OCSP response, which shall
 correspond to the time produced as contained in the issued OCSP
 response.  Since it may be needed to make the difference between two
 OCSP responses received within the same second, the hash of the
 response contained in the OcspResponsesID may be needed to solve the
 ambiguity.
    NOTE 1: Copies of the CRL and OCSP responses values may be held
    using the revocation-values attribute defined in Section 6.3.4.
    NOTE 2: It is recommended that this attribute be used in
    preference to the OtherRevocationInfoFormat specified in RFC 3852
    to maintain backwards compatibility with the earlier version of
    this specification.
 The syntax and semantics of other revocation references are outside
 the scope of the present document.  The definition of the syntax of
 the other form of revocation information is as identified by
 OtherRevRefType.
 This attribute may include the references to the full set of the CRL,
 ACRL, or OCSP responses that have been used to verify the
 certification chain for any TSUs that provide time-stamp tokens.  In
 this case, the unsigned attribute shall be added to the signedData of
 the relevant time-stamp token as an unsignedAttrs in the signerInfos
 field.

6.2.3. attribute-certificate-references Attribute Definition

 This attribute is only used when a user attribute certificate is
 present in the electronic signature.
 The attribute-certificate-references attribute is an unsigned
 attribute.  It references the full set of AA certificates that have

Pinkas, et al. Informational [Page 51] RFC 5126 CMS Advanced Electronic Signatures February 2008

 been used to validate the attribute certificate.  Only a single
 instance of this attribute shall occur with an electronic signature.
 id-aa-ets-attrCertificateRefs OBJECT IDENTIFIER ::=
 { iso(1) member-body(2) us(840) rsadsi(113549) pkcs(1) pkcs-9(9)
 smime(16) id-aa(2) 44}
 The attribute-certificate-references attribute value has the ASN.1
 syntax AttributeCertificateRefs:
 AttributeCertificateRefs ::=  SEQUENCE OF OtherCertID
 OtherCertID is defined in Section 5.7.3.3.
    NOTE: Copies of the certificate values may be held using the
    certificate-values attribute defined in Section 6.3.3.

6.2.4. attribute-revocation-references Attribute Definition

 This attribute is only used when a user attribute certificate is
 present in the electronic signature and when that attribute
 certificate can be revoked.
 The attribute-revocation-references attribute is an unsigned
 attribute.  Only a single instance of this attribute shall occur with
 an electronic signature.  It references the full set of the ACRL or
 OCSP responses that have been used in the validation of the attribute
 certificate.  This attribute can be used to illustrate that the
 verifier has taken due diligence of the available revocation
 information.
 The following object identifier identifies the
 attribute-revocation-references attribute:
 id-aa-ets-attrRevocationRefs OBJECT IDENTIFIER ::= { iso(1)
 member-body(2) us(840) rsadsi(113549) pkcs(1) pkcs-9(9) smime(16)
 id-aa(2) 45}
 The attribute-revocation-references attribute value has the ASN.1
 syntax AttributeRevocationRefs:
 AttributeRevocationRefs ::=  SEQUENCE OF CrlOcspRef

6.3. Extended Validation Data (CAdES-X)

 This section specifies a number of optional attributes that are used
 by extended forms of electronic signatures (see Annex B for an
 overview of these forms of validation data).

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6.3.1. Time-Stamped Validation Data (CAdES-X Type 1 or Type 2)

 The extended validation data may include one of the following
 additional attributes, forming a CAdES-X Time-Stamp validation data
 (CAdES-X Type 1 or CAdES-X Type 2), to provide additional protection
 against later CA compromise and provide integrity of the validation
 data used:
  1. CAdES-C Time-stamp, as defined in Section 6.3.5 (CAdES-X Type

1); or

  1. Time-Stamped Certificates and CRLs references, as defined in

Section 6.3.6 (CAdES-X Type 2).

6.3.2. Long Validation Data (CAdES-X Long, CAdES-X Long Type 1 or 2)

 The extended validation data may also include the following
 additional information, forming a CAdES-X Long, for use if later
 validation processes may not have access to this information:
  1. certificate-values, as defined in Section 6.3.3; and
  1. revocation-values, as defined in Section 6.3.4.
 The extended validation data may, in addition to certificate-values
 and revocation-values as defined in Sections 6.3.3 and 6.3.4, include
 one of the following additional attributes, forming a CAdES-X Long
 Type 1 or CAdES-X Long Type 2.
  1. CAdES-C Time-stamp, as defined in Section 6.3.3 (CAdES-X long

Type 1); or

  1. Time-Stamped Certificates and CRLs references, as defined in

Section 6.3.4 (CAdES-X Long Type 2).

 The CAdES-X Long Type 1 or CAdES-X Long Type 2 provides additional
 protection against later CA compromise and provides integrity of the
 validation data used.
    NOTE 1: The CAdES-X-Long signature provides long-term proof of the
    validity of the signature for as long as the CA keys, CRL Issuers
    keys, and OCSP responder keys are not compromised and are
    resistant to cryptographic attacks.
    NOTE 2: As long as the time-stamp data remains valid, the CAdES-X
    Long Type 1 and the CAdES-X Long Type 2 provide the following
    important property for long-standing signatures; that having been
    found once to be valid, it shall continue to be so months or years

Pinkas, et al. Informational [Page 53] RFC 5126 CMS Advanced Electronic Signatures February 2008

    later, long after the validity period of the certificates has
    expired, or after the user key has been compromised.

6.3.3. certificate-values Attribute Definition

 This attribute may be used to contain the certificate information
 required for the following forms of extended electronic signature:
 CAdES-X Long, ES X-Long Type 1, and CAdES-X Long Type 2; see Annex
 B.1.1 for an illustration of this form of electronic signature.
 The certificate-values attribute is an unsigned attribute.  Only a
 single instance of this attribute shall occur with an electronic
 signature.  It holds the values of certificates referenced in the
 complete-certificate-references attribute.
    NOTE: If an attribute certificate is used, it is not provided in
    this structure but shall be provided by the signer as a
    signer-attributes attribute (see Section 5.11.3).
 The following object identifier identifies the certificate-values
 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 Section 7.1. (which is as defined in ITU-T
 Recommendation X.509 [1]).
 This attribute may include the certification information for any TSUs
 that have provided the time-stamp tokens, if these certificates are
 not already included in the TSTs as part of the TSUs signatures.  In
 this case, the unsigned attribute shall be added to the signedData of
 the relevant time-stamp token.

6.3.4. revocation-values Attribute Definition

 This attribute is used to contain the revocation information required
 for the following forms of extended electronic signature: CAdES-X
 Long, ES X-Long Type 1, and CAdES-X Long Type 2; see Annex B.1.1 for
 an illustration of this form of electronic signature.
 The revocation-values attribute is an unsigned attribute.  Only a
 single instance of this attribute shall occur with an electronic

Pinkas, et al. Informational [Page 54] RFC 5126 CMS Advanced Electronic Signatures February 2008

 signature.  It holds the values of CRLs and OCSP referenced in the
 complete-revocation-references attribute.
    NOTE: It is recommended that this attribute be used in preference
    to the OtherRevocationInfoFormat specified in RFC 3852 to maintain
    backwards compatibility with the earlier version of this
    specification.
 The following object identifier identifies the revocation-values
 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 OPTIONAL }
 OtherRevVals ::= SEQUENCE {
    OtherRevValType   OtherRevValType,
    OtherRevVals      ANY DEFINED BY OtherRevValType }
 OtherRevValType ::= OBJECT IDENTIFIER
 The syntax and semantics of the other revocation values
 (OtherRevVals) are outside the scope of the present document.
 The definition of the syntax of the other form of revocation
 information is as identified by OtherRevRefType.
 CertificateList is defined in Section 7.2. (which is as defined in
 ITU-T Recommendation X.509 [1]).
 BasicOCSPResponse is defined in Section 7.3. (which is as defined in
 RFC 2560 [3]).
 This attribute may include the values of revocation data including
 CRLs and OCSPs for any TSUs that have provided the time-stamp tokens,
 if these certificates are not already included in the TSTs as part of
 the TSUs signatures.  In this case, the unsigned attribute shall be
 added to the signedData of the relevant time-stamp token.

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6.3.5. CAdES-C-time-stamp Attribute Definition

 This attribute is used to protect against CA key compromise.
 This attribute is used for the time-stamping of the complete
 electronic signature (CAdES-C).  It is used in the following forms of
 extended electronic signature; CAdES-X Type 1 and CAdES-X Long Type
 1; see Annex B.1.2 for an illustration of this form of electronic
 signature.
 The CAdES-C-time-stamp attribute is an unsigned attribute.  It is a
 time-stamp token of the hash of the electronic signature and the
 complete validation data (CAdES-C).  It is a special-purpose
 TimeStampToken Attribute that time-stamps the CAdES-C.  Several
 instances of this attribute may occur with an electronic signature
 from different TSAs.
    NOTE 1: It is recommended that the attributes being time-stamped
    be encoded in DER.  If DER is not employed, then the binary
    encoding of the ASN.1 structures being time-stamped should be
    preserved to ensure that the recalculation of the data hash is
    consistent.
    NOTE 2: Each attribute is included in the hash with the attrType
    and attrValues (including type and length) but without the type
    and length of the outer SEQUENCE.
 The following object identifier identifies the CAdES-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}
 The CAdES-C-timestamp attribute value has the ASN.1 syntax
 ESCTimeStampToken :
 ESCTimeStampToken ::= TimeStampToken
 The value of the messageImprint field within TimeStampToken shall be
 a hash of the concatenated values (without the type or length
 encoding for that value) of the following data objects:
  1. OCTETSTRING of the SignatureValue field within SignerInfo;
  1. signature-time-stamp, or a time-mark operated by a Time-Marking

Authority;

  1. complete-certificate-references attribute; and

Pinkas, et al. Informational [Page 56] RFC 5126 CMS Advanced Electronic Signatures February 2008

  1. complete-revocation-references attribute.
 For further information and definition of the TimeStampToken, see
 Section 7.4.

6.3.6. time-stamped-certs-crls-references Attribute Definition

 This attribute is used to protect against CA key compromise.  This
 attribute is used for the time-stamping certificate and revocation
 references.  It is used in the following forms of extended electronic
 signature: CAdES-X Type 2 and CAdES-X Long Type 2; see Annex B.1.3
 for an illustration of this form of electronic signature.
 A time-stamped-certs-crls-references attribute is an unsigned
 attribute.  It is a time-stamp token issued for a list of referenced
 certificates and OCSP responses and/or CRLs to protect against
 certain CA compromises.  Its syntax is as follows:
    NOTE 1: It is recommended that the attributes being time-stamped
    be encoded in DER.  If DER is not employed, then the binary
    encoding of the ASN.1 structures being time-stamped should be
    preserved to ensure that the recalculation of the data hash is
    consistent.
    NOTE 2: Each attribute is included in the hash with the attrType
    and attrValues (including type and length) but without the type
    and length of the outer SEQUENCE.
 The following object identifier identifies the
 time-stamped-certs-crls-references 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 the messageImprint field within the TimeStampToken shall
 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 (CAdES-C):
  1. complete-certificate-references attribute; and
  1. complete-revocation-references attribute.

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6.4. Archive Validation Data

 Where an electronic signature is required to last for a very long
 time, and the time-stamp token on an electronic signature is in
 danger of being invalidated due to algorithm weakness or limits in
 the validity period of the TSA certificate, it may be required to
 time-stamp the electronic signature several times.  When this is
 required, an archive time-stamp attribute may be required for the
 archive form of the electronic signature (CAdES-A).  This archive
 time-stamp attribute may be repeatedly applied over a period of time.

6.4.1. archive-time-stamp Attribute Definition

 The archive-time-stamp attribute is a time-stamp token of many of the
 elements of the signedData in the electronic signature.  If the
 certificate-values and revocation-values attributes are not present
 in the CAdES-BES or CAdES-EPES, then they shall be added to the
 electronic signature prior to computing the archive time-stamp token.
 The archive-time-stamp attribute is an unsigned attribute.  Several
 instances of this attribute may occur with an electronic signature
 both over time and from different TSUs.
 The following object identifier identifies the nested
 archive-time-stamp attribute:
 id-aa-ets-archiveTimestampV2  OBJECT IDENTIFIER ::=
 { iso(1) member-body(2) us(840) rsadsi(113549) pkcs(1) pkcs-9(9)
 smime(16) id-aa(2) 48}
 Archive-time-stamp attribute values have the ASN.1 syntax
 ArchiveTimeStampToken
 ArchiveTimeStampToken ::= TimeStampToken
 The value of the messageImprint field within TimeStampToken shall be
 a hash of the concatenation of:
  1. the encapContentInfo element of the SignedData sequence;
  1. any external content being protected by the signature, if the

eContent element of the encapContentInfo is omitted;

  1. the Certificates and crls elements of the SignedData sequence,

when present, and;

  1. all data elements in the SignerInfo sequence including all

signed and unsigned attributes.

Pinkas, et al. Informational [Page 58] RFC 5126 CMS Advanced Electronic Signatures February 2008

    NOTE 1: An alternative archiveTimestamp attribute, identified by
    an object identifier { iso(1) member-body(2) us(840)
    rsadsi(113549) pkcs(1) pkcs-9(9) smime(16) id-aa(2) 27, is defined
    in prior versions of TS 101 733 [TS101733] and in RFC 3126.
    The archiveTimestamp attribute, defined in versions of TS 101 733
    prior to 1.5.1 and in RFC 3126, is not compatible with the
    attribute defined in the current document.  The archiveTimestamp
    attribute, defined in versions 1.5.1 to 1.6.3 of TS 101 733, is
    compatible with the current document if the content is internal to
    encapContentInfo.  Unless the version of TS 101 733 employed by
    the signing party is known by all recipients, use of the
    archiveTimestamp attribute defined in prior versions of TS 101 733
    is deprecated.
    NOTE 2: Counter signatures held as countersignature attributes do
    not require independent archive time-stamps, as they are protected
    by the archive time-stamp against the containing SignedData
    structure.
    NOTE 3: Unless DER is used throughout, it is recommended that the
    binary encoding of the ASN.1 structures being time-stamped be
    preserved when being archived to ensure that the recalculation of
    the data hash is consistent.
    NOTE 4: The hash is calculated over the concatenated data elements
    as received/stored, including the Type and Length encoding.
    NOTE 5: Whilst it is recommended that unsigned attributes be DER
    encoded, it cannot generally be so guaranteed except by prior
    arrangement.  For further information and definition of
    TimeStampToken, see Section 7.4.  The timestamp should be created
    using stronger algorithms (or longer key lengths) than in the
    original electronic signatures and weak algorithm (key length)
    timestamps.
    NOTE 6: This form of ES also provides protection against a TSP key
    compromise.
 The ArchiveTimeStamp will be added as an unsigned attribute in the
 SignerInfo sequence.  For the validation of one ArchiveTimeStamp, the
 data elements of the SignerInfo must be concatenated, excluding all
 later ArchivTimeStampToken attributes.
 Certificates and revocation information required to validate the
 ArchiveTimeStamp shall be provided by one of the following methods:

Pinkas, et al. Informational [Page 59] RFC 5126 CMS Advanced Electronic Signatures February 2008

  1. The TSU provides the information in the SignedData of the

timestamp token;

  1. Adding the complete-certificate-references attribute and the

complete-revocation-references attribute of the TSP as an

      unsigned attribute within TimeStampToken, when the required
      information is stored elsewhere; or
  1. Adding the certificate-values attribute and the

revocation-values attribute of the TSP as an unsigned attribute

      within TimeStampToken, when the required information is stored
      elsewhere.

7. Other Standard Data Structures

7.1. Public Key Certificate Format

 The X.509 v3 certificate basis syntax is defined in ITU-T
 Recommendation X.509 [1].  A profile of the X.509 v3 certificate is
 defined in RFC 3280 [2].

7.2. Certificate Revocation List Format

 The X.509 v2 CRL syntax is defined in ITU-T Recommendation X.509 [1].
 A profile of the X.509 v2 CRL is defined in RFC 3280 [2].

7.3. OCSP Response Format

 The format of an OCSP token is defined in RFC 2560 [3].

7.4. Time-Stamp Token Format

 The format of a TimeStampToken type is defined in RFC 3161 [7] and
 profiled in ETSI TS 101 861 [TS101861].

7.5. Name and Attribute Formats

 The syntax of the naming and other attributes is defined in ITU-T
 Recommendation X.509 [1].
    NOTE: The name used by the signer, held as the subject in the
    signer's certificate, is allocated and verified on registration
    with the Certification Authority, either directly or indirectly
    through a Registration Authority, before being issued with a
    Certificate.

Pinkas, et al. Informational [Page 60] RFC 5126 CMS Advanced Electronic Signatures February 2008

 The present 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 [12], held in the subject field of the
 certificate, or any other name form held in the subjectAltName
 certificate extension field, as defined in ITU-T Recommendation X.509
 [1].  In the case that the subject has no distinguished name, the
 subject name can be an empty sequence and the subjectAltName
 extension shall be critical.
 All Certification Authorities, Attribute Authorities, and
 Time-Stamping Authorities shall use distinguished names in the
 subject field of their certificate.
 The distinguished name shall include identifiers for the organization
 providing the service and the legal jurisdiction (e.g., country)
 under which it operates.
 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, which 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, one of the
 two identities is carried in the subject/subjectAltName field of the
 signer's certificate as described above.
 The present document does not specify the format of the signer's
 attribute that may be included in public key certificates.
    NOTE: The signer's attribute may be supported by using a claimed
    role in the CMS signed attributes field or by placing an attribute
    certificate containing a certified role in the CMS signed
    attributes field; see Section 7.6.

7.6. AttributeCertificate

 The syntax of the AttributeCertificate type is defined in RFC 3281
 [13].

8. Conformance Requirements

 For implementations supporting signature generation, the present
 document defines conformance requirements for the generation of two
 forms of basic electronic signature, one of the two forms must be
 implemented.

Pinkas, et al. Informational [Page 61] RFC 5126 CMS Advanced Electronic Signatures February 2008

 For implementations supporting signature verification, the present
 document defines conformance requirements for the verification of two
 forms of basic electronic signature, one of the two forms must be
 implemented.
 The present document only defines conformance requirements up to an
 ES with Complete validation data (CAdES-C).  This means that none of
 the extended and archive forms of the electronic signature (CAdES-X,
 CAdES-A) need to be implemented to get conformance to the present
 document.
 On verification the inclusion of optional signed and unsigned
 attributes must be supported only to the extent that the signature is
 verifiable.  The semantics of optional attributes may be unsupported,
 unless specified otherwise by a signature policy.

8.1. CAdES-Basic Electronic Signature (CAdES-BES)

 A system supporting CAdES-BES signers, according to the present
 document, shall, at a minimum, support generation of an electronic
 signature consisting of the following components:
  1. The general CMS syntax and content type, as defined in RFC 3852

[4] (see Sections 5.1 and 5.2);

  1. CMS SignedData, as defined in RFC 3852 [4], with the version set

to 3 and at least one SignerInfo present (see Sections 5.3 to

      5.6);
  1. The following CMS attributes, as defined in RFC 3852 [4]:
  1. content-type; this shall always be present (see Section

5.7.1); and

  1. message-digest; this shall always be present (see Section

5.7.2).

  1. One of the following attributes, as defined in the present

document:

  1. signing-certificate: as defined in Section 5.7.3.1; or
  2. signing-certificate v2 : as defined in Section 5.7.3.2.
    NOTE: RFC 3126 was using the other signing-certificate attribute
    (see Section 5.7.3.3).  Its use is now deprecated, since the
    structure of the signing-certificate v2 attribute is simpler than
    the other signing-certificate attribute.

Pinkas, et al. Informational [Page 62] RFC 5126 CMS Advanced Electronic Signatures February 2008

8.2. CAdES-Explicit Policy-based Electronic Signature

 A system supporting Policy-based signers, according to the present
 document, shall, at a minimum, support the generation of an
 electronic signature consisting of the previous components defined
 for the basic signer, plus:
  1. The following attributes, as defined in Section 5.9:
  1. signature-policy-identifier; this shall always be present

(see Section 5.8.1).

8.3. Verification Using Time-Stamping

 A system supporting verifiers, according to the present document,
 with time-stamping facilities shall, at a minimum, support:
  1. verification of the mandated components of an electronic

signature, as defined in Section 8.1;

  1. signature-time-stamp attribute, as defined in Section 6.1.1;
  1. complete-certificate-references attribute, as defined in Section

6.2.1;

  1. complete-revocation-references attribute, as defined in Section

6.2.2;

  1. Public Key Certificates, as defined in ITU-T Recommendation

X.509 [1] (see Section 8.1); and

  1. either of:
  1. Certificate Revocation Lists, as defined in ITU-T

Recommendation X.509 [1] (see Section 8.2); or

  1. Online Certificate Status Protocol, as defined in RFC 2560

[3] (see Section 8.3).

8.4. Verification Using Secure Records

 A system supporting verifiers, according to the present document,
 shall, at a minimum, support:
  1. verification of the mandated components of an electronic

signature, as defined in Section 8.1;

Pinkas, et al. Informational [Page 63] RFC 5126 CMS Advanced Electronic Signatures February 2008

  1. complete-certificate-references attribute, as defined in Section

6.2.1;

  1. complete-revocation-references attribute, as defined in Section

6.2.2;

  1. a record of the electronic signature and the time when the

signature was first validated, using the referenced certificates

      and revocation information, must be maintained, such that
      records cannot be undetectably modified;
  1. Public Key Certificates, as defined in ITU-T Recommendation

X.509 [1] (see Section 8.1); and

  1. either of:
  1. Certificate Revocation Lists, as defined in ITU-T

Recommendation X.509 [1] (see Section 8.2); or

  1. online Certificate Status Protocol, as defined in RFC 2560

[3] (see Section 8.3).

9. References

9.1. Normative References

 [1]    ITU-T Recommendation X.509 (2000)/ISO/IEC 9594-8 (2001):
        "Information technology - Open Systems Interconnection - The
        Directory: Public key and Attribute Certificate framework".
 [2]    Housley, R., Polk, W., Ford, W., and D. Solo, "Internet X.509
        Public Key Infrastructure Certificate and Certificate
        Revocation List (CRL) Profile", RFC 3280, April 2002.
 [3]    Myers, M., Ankney, R., Malpani, A., Galperin, S., and C.
        Adams, "X.509 Internet Public Key Infrastructure Online
        Certificate Status Protocol - OCSP", RFC 2560, June 1999.
 [4]    Housley, R., "Cryptographic Message Syntax (CMS)", RFC 3852,
        July 2004.
 [5]    Hoffman, P., Ed., "Enhanced Security Services for S/MIME", RFC
        2634, June 1999.
 [6]    Freed, N. and N. Borenstein, "Multipurpose Internet Mail
        Extensions (MIME) Part One: Format of Internet Message
        Bodies", RFC 2045, November 1996.

Pinkas, et al. Informational [Page 64] RFC 5126 CMS Advanced Electronic Signatures February 2008

 [7]    Adams, C., Cain, P., Pinkas, D., and R. Zuccherato, "Internet
        X.509 Public Key Infrastructure Time-Stamp Protocol (TSP)",
        RFC 3161, August 2001.
 [8]    ITU-T Recommendation X.680 (1997): "Information technology -
        Abstract Syntax Notation One (ASN.1): Specification of basic
        notation".
 [9]    ITU-T Recommendation X.501 (2000)/ISO/IEC 9594-1 (2001):
        "Information technology - Open Systems Interconnection -
        Directory models".
 [10]   Housley, R., "Cryptographic Message Syntax (CMS) Algorithms",
        RFC 3370, August 2002.
 [11]   ITU-T Recommendation F.1: "Operational provisions for the
        international public telegram service".
 [12]   ITU-T Recommendation X.500: "Information technology - Open
        Systems Interconnection - The Directory: Overview of concepts,
        models and services".
 [13]   Farrell, S. and R. Housley, "An Internet Attribute Certificate
        Profile for Authorization", RFC 3281, April 2002.
 [14]   ITU-T Recommendation X.208 (1988): "Specification of Abstract
        Syntax Notation One (ASN.1)".
 [15]   Schaad, J., "Enhanced Security Services (ESS) Update: Adding
        CertID Algorithm Agility", RFC 5035, August 2007.
 [16]   ITU-T Recommendation X.690 (2002): "Information technology
        ASN.1 encoding rules: Specification of Basic Encoding Rules
        (BER), Canonical Encoding Rules (CER) and Distinguished
        Encoding Rules (DER)".

9.2. Informative References

 [EUDirective]  Directive 1999/93/EC of the European Parliament and of
                the Council of 13 December 1999 on a community
                framework for Electronic Signatures.
 [TS101733]     ETSI Standard TS 101 733 V.1.7.3 (2005-06) Electronic
                Signature Formats.
 [TS101861]     ETSI TS 101 861: "Time stamping profile".

Pinkas, et al. Informational [Page 65] RFC 5126 CMS Advanced Electronic Signatures February 2008

 [TS101903]     ETSI TS 101 903: "XML Advanced Electronic Signatures
                (XAdES)".
 [TR102038]     ETSI TR 102 038: "Electronic Signatures and
                Infrastructures (ESI); XML format for signature
                policies".
 [TR102272]     ETSI TR 102 272 V1.1.1 (2003-12). "Electronic
                Signatures and Infrastructures (ESI); ASN.1 format for
                signature policies".
 [RFC2479]      Adams, C., "Independent Data Unit Protection Generic
                Security Service Application Program Interface (IDUP-
                GSS-API)", RFC 2479, December 1998.
 [RFC2743]      Linn, J., "Generic Security Service Application
                Program Interface Version 2, Update 1", RFC 2743,
                January 2000.
 [RFC3125]      Ross, J., Pinkas, D., and N. Pope, "Electronic
                Signature Policies", RFC 3125, September 2001.
 [RFC3447]      Jonsson, J. and B. Kaliski, "Public-Key Cryptography
                Standards (PKCS) #1: RSA Cryptography Specifications
                Version 2.1", RFC 3447, February 2003.
 [RFC3494]      Zeilenga, K., "Lightweight Directory Access Protocol
                version 2 (LDAPv2) to Historic Status", RFC 3494,
                March 2003.
 [RFC3851]      Ramsdell, B., Ed., "Secure/Multipurpose Internet Mail
                Extensions (S/MIME) Version 3.1 Message
                Specification", RFC 3851, July 2004.
 [RFC4210]      Adams, C., Farrell, S., Kause, T., and T. Mononen,
                "Internet X.509 Public Key Infrastructure Certificate
                Management Protocol (CMP)", RFC 4210, September 2005.
 [RFC4346]      Dierks, T. and E. Rescorla, "The Transport Layer
                Security (TLS) Protocol Version 1.1", RFC 4346, April
                2006.
 [RFC4523]      Zeilenga, K., "Lightweight Directory Access Protocol
                (LDAP) Schema Definitions for X.509 Certificates", RFC
                4523, June 2006.

Pinkas, et al. Informational [Page 66] RFC 5126 CMS Advanced Electronic Signatures February 2008

 [ISO7498-2]    ISO 7498-2 (1989): "Information processing systems -
                Open Systems Interconnection - Basic Reference Model -
                Part 2: Security Architecture".
 [ISO9796-2]    ISO/IEC 9796-2 (2002): "Information technology -
                Security techniques - Digital signature schemes giving
                message recovery - Part 2: Integer factorization based
                mechanisms".
 [ISO9796-4]    ISO/IEC 9796-4 (1998): "Digital signature schemes
                giving message recovery - Part 4: Discrete logarithm
                based mechanisms".
 [ISO10118-1]   ISO/IEC 10118-1 (2000): "Information technology -
                Security techniques - Hash-functions - Part 1:
                General".
 [ISO10118-2]   ISO/IEC 10118-2 (2000): "Information technology -
                Security techniques - Hash-functions - Part 2:
                Hash-functions using an n-bit block cipher algorithm".
 [ISO10118-3]   ISO/IEC 10118-3 (2004): "Information technology -
                Security techniques - Hash-functions - Part 3:
                Dedicated hash-functions".
 [ISO10118-4]   ISO/IEC 10118-4 (1998): "Information technology -
                Security techniques - Hash-functions - Part 4: Hash-
                functions using modular arithmetic".
 [ISO10181-5]   ISO/IEC 10181-5:  Security Frameworks in Open Systems.
                Non-Repudiation Framework.  April 1997.
 [ISO13888-1]   ISO/IEC 13888-1 (2004): "IT security techniques -
                Non-repudiation - Part 1: General".
 [ISO14888-1]   ISO/IEC 14888-1 (1998): "Information technology -
                Security techniques - Digital signatures with appendix
                - Part 1: General".
 [ISO14888-2]   ISO/IEC 14888-2 (1999): "Information technology -
                Security techniques - Digital signatures with appendix
                - Part 2: Identity-based mechanisms".
 [ISO14888-3]   ISO/IEC 14888-3 (1998): "Information technology -
                Security techniques - Digital signatures with appendix
                - Part 3: Certificate-based mechanisms".

Pinkas, et al. Informational [Page 67] RFC 5126 CMS Advanced Electronic Signatures February 2008

 [ISO15946-2]   ISO/IEC 15946-2 (2002): "Information technology -
                Security techniques - Cryptographic techniques based
                on elliptic curves - Part 2: Digital signatures".
 [CWA14171]     CWA 14171 CEN Workshop Agreement: "General Guidelines
                for Electronic Signature Verification".
 [XMLDSIG]      XMLDSIG: W3C/IETF Recommendation (February 2002):
                "XML-Signature Syntax and Processing".
 [X9.30-1]      ANSI X9.30-1 (1997): "Public Key Cryptography for the
                Financial Services Industry - Part 1: The Digital
                Signature Algorithm (DSA)".
 [X9.30-2]      ANSI X9.30-2 (1997): "Public Key Cryptography for the
                Financial Services Industry - Part 2: The Secure Hash
                Algorithm (SHA-1)".
 [X9.31-1]      ANSI X9.31-1 (1997): "Public Key Cryptography Using
                Reversible Algorithms for the Financial Services
                Industry - Part 1: The RSA Signature Algorithm".
 [X9.31-2]      ANSI X9.31-2 (1996): "Public Key Cryptography Using
                Reversible Algorithms for the Financial Services
                Industry - Part 2: Hash Algorithms".
 [X9.62]        ANSI X9.62 (1998): "Public Key Cryptography for the
                Financial Services Industry - The Elliptic Curve
                Digital Signature Algorithm (ECDSA)".
 [P1363]        IEEE P1363 (2000): "Standard Specifications for
                Public-Key Cryptography".
 ETSI technical specifications can be downloaded free of charge via
 the Services and Products Download Area at:
 http://www.etsi.org/WebSite/Standards/StandardsDownload.aspx

Pinkas, et al. Informational [Page 68] RFC 5126 CMS Advanced Electronic Signatures February 2008

Annex A (Normative): ASN.1 Definitions

 This annex provides a summary of all the ASN.1 syntax definitions for
 new syntax defined in the present document.

A.1. Signature Format Definitions Using X.208 ASN.1 Syntax

    NOTE: The ASN.1 module defined in Annex A.1 using syntax defined
    in ITU-T Recommendation X.208 [14] has precedence over that
    defined in Annex A.2 in the case of any conflict.

ETS-ElectronicSignatureFormats-ExplicitSyntax88 { iso(1) member-body(2) us(840) rsadsi(113549) pkcs(1) pkcs-9(9) smime(16) id-mod(0) eSignature-explicit88(28)}

DEFINITIONS EXPLICIT TAGS ::=

BEGIN

– EXPORTS All

IMPORTS

– Cryptographic Message Syntax (CMS): RFC 3852

 ContentInfo, ContentType, id-data, id-signedData, SignedData,
 EncapsulatedContentInfo, SignerInfo, id-contentType,
 id-messageDigest, MessageDigest, id-signingTime, SigningTime,
 id-countersignature, Countersignature
    FROM CryptographicMessageSyntax2004
    { iso(1) member-body(2) us(840) rsadsi(113549) pkcs(1) pkcs-9(9)
    smime(16) modules(0) cms-2004(24) }

– ESS Defined attributes: ESS Update – RFC 5035 (Adding CertID Algorithm Agility)

 id-aa-signingCertificate, SigningCertificate, IssuerSerial,
 id-aa-contentReference, ContentReference, id-aa-contentIdentifier,
 ContentIdentifier, id-aa-signingCertificateV2
    FROM 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) }

– Internet X.509 Public Key Infrastructure - Certificate and CRL – Profile: RFC 3280

 Certificate, AlgorithmIdentifier, CertificateList, Name,
 DirectoryString, Attribute, BMPString, UTF8String

Pinkas, et al. Informational [Page 69] RFC 5126 CMS Advanced Electronic Signatures February 2008

    FROM PKIX1Explicit88
    {iso(1) identified-organization(3) dod(6) internet(1)
    security(5) mechanisms(5) pkix(7) id-mod(0) id-pkix1-explicit(18)}
 GeneralNames, GeneralName, PolicyInformation
    FROM PKIX1Implicit88
    {iso(1) identified-organization(3) dod(6) internet(1) security(5)
     mechanisms(5) pkix(7) id-mod(0) id-pkix1-implicit (19)}

– Internet Attribute Certificate Profile for Authorization - RFC 3281

 AttributeCertificate
    FROM PKIXAttributeCertificate {iso(1) identified-organization(3)
              dod(6) internet(1) security(5) mechanisms(5) pkix(7)
              id-mod(0) id-mod-attribute-cert(12)}

– OCSP - RFC 2560

 BasicOCSPResponse, ResponderID
    FROM OCSP {iso(1) identified-organization(3) dod(6) internet(1)
    security(5) mechanisms(5) pkix(7) id-mod(0) id-mod-ocsp(14)}

– Time Stamp Protocol RFC 3161

 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)}

;

– Definitions of Object Identifier arcs used in the present document –

– OID used referencing electronic signature mechanisms based on – the present document for use with the Independent Data Unit – Protection (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) }

– Basic ES CMS Attributes Defined in the present document –

Pinkas, et al. Informational [Page 70] RFC 5126 CMS Advanced Electronic Signatures February 2008

– OtherSigningCertificate - deprecated

  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 THE PRESENT DOCUMENT
 }
 OtherCertID ::= SEQUENCE {
    otherCertHash            OtherHash,
    issuerSerial             IssuerSerial OPTIONAL }
 OtherHash ::= CHOICE {
     sha1Hash     OtherHashValue,
     -- This contains a SHA-1 hash
     otherHash    OtherHashAlgAndValue}

– Policy ES Attributes Defined in the present document –

– Mandatory Basic Electronic Signature Attributes as above, – plus in addition.

– 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 }
 SignaturePolicy ::= CHOICE {
    signaturePolicyId          SignaturePolicyId,
    signaturePolicyImplied     SignaturePolicyImplied
                               --  not used in this version
 }
 SignaturePolicyId ::= SEQUENCE {
    sigPolicyId        SigPolicyId,
    sigPolicyHash      SigPolicyHash,
    sigPolicyQualifiers   SEQUENCE SIZE (1..MAX) OF
                                 SigPolicyQualifierInfo OPTIONAL
 }
 SignaturePolicyImplied ::= NULL

Pinkas, et al. Informational [Page 71] RFC 5126 CMS Advanced Electronic Signatures February 2008

 SigPolicyId ::= OBJECT IDENTIFIER
 SigPolicyHash ::= OtherHashAlgAndValue
 OtherHashAlgAndValue ::= SEQUENCE {
    hashAlgorithm   AlgorithmIdentifier,
    hashValue       OtherHashValue }
 OtherHashValue ::= OCTET STRING
 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 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}

 CommitmentTypeIndication ::= SEQUENCE {

Pinkas, et al. Informational [Page 72] RFC 5126 CMS Advanced Electronic Signatures February 2008

   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 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}

 SignerLocation ::= SEQUENCE {
     -- at least one of the following shall 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 attribute

Pinkas, et al. Informational [Page 73] RFC 5126 CMS Advanced Electronic Signatures February 2008

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 RFC 3281: see Section 4.1

– Content-time-stamp 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}

 ContentTimestamp ::= TimeStampToken

– Signature-time-stamp 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}

SignatureTimeStampToken ::= TimeStampToken

– Complete-certificate-references attribute

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-references 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}

 CompleteRevocationRefs ::=  SEQUENCE OF CrlOcspRef
 CrlOcspRef ::= SEQUENCE {
    crlids          [0] CRLListID   OPTIONAL,
    ocspids         [1] OcspListID  OPTIONAL,
    otherRev        [2] OtherRevRefs OPTIONAL
 }

Pinkas, et al. Informational [Page 74] RFC 5126 CMS Advanced Electronic Signatures February 2008

 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 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}

 CertificateValues ::=  SEQUENCE OF Certificate

– Certificate-revocation-values 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}

 RevocationValues ::=  SEQUENCE {

Pinkas, et al. Informational [Page 75] RFC 5126 CMS Advanced Electronic Signatures February 2008

    crlVals           [0] SEQUENCE OF CertificateList OPTIONAL,
    ocspVals          [1] SEQUENCE OF BasicOCSPResponse OPTIONAL,
    otherRevVals      [2] OtherRevVals OPTIONAL}
 OtherRevVals ::= SEQUENCE {
     otherRevValType   OtherRevValType,
     otherRevVals      ANY DEFINED BY otherRevValType
 }
 OtherRevValType ::= OBJECT IDENTIFIER

– CAdES-C time-stamp 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}

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 attribute id-aa-ets-archiveTimestampV2 OBJECT IDENTIFIER ::= { iso(1) member-body(2) us(840) rsadsi(113549) pkcs(1) pkcs-9(9) smime(16) id-aa(2) 48}

ArchiveTimeStampToken ::= TimeStampToken

– Attribute-certificate-references attribute

id-aa-ets-attrCertificateRefs OBJECT IDENTIFIER ::= { iso(1) member-body(2) us(840) rsadsi(113549) pkcs(1) pkcs-9(9) smime(16) id-aa(2) 44}

AttributeCertificateRefs ::= SEQUENCE OF OtherCertID

– Attribute-revocation-references attribute

id-aa-ets-attrRevocationRefs OBJECT IDENTIFIER ::= { iso(1) member-body(2) us(840) rsadsi(113549) pkcs(1) pkcs-9(9) smime(16) id-aa(2) 45}

AttributeRevocationRefs ::= SEQUENCE OF CrlOcspRef

Pinkas, et al. Informational [Page 76] RFC 5126 CMS Advanced Electronic Signatures February 2008

END

A.2. Signature Format Definitions Using X.680 ASN.1 Syntax

    NOTE: The ASN.1 module defined in Annex A.1 has precedence over
    that defined in Annex A.2 using syntax defined in ITU-T
    Recommendation X.680 (1997) [8] in the case of any conflict.

ETS-ElectronicSignatureFormats-ExplicitSyntax97 { iso(1) member-body(2) us(840) rsadsi(113549) pkcs(1) pkcs-9(9) smime(16) id-mod(0) eSignature-explicit97(29)}

DEFINITIONS EXPLICIT TAGS ::=

BEGIN

– EXPORTS All -

IMPORTS

– Cryptographic Message Syntax (CMS): RFC 3852

 ContentInfo, ContentType, id-data, id-signedData, SignedData,
 EncapsulatedContentInfo, SignerInfo,
 id-contentType, id-messageDigest, MessageDigest, id-signingTime,
 SigningTime, id-countersignature, Countersignature
    FROM CryptographicMessageSyntax2004
    { iso(1) member-body(2) us(840) rsadsi(113549) pkcs(1) pkcs-9(9)
     smime(16) modules(0) cms-2004(24) }

– ESS Defined attributes: ESS Update – RFC 5035 (Adding CertID Algorithm Agility)

 id-aa-signingCertificate, SigningCertificate, IssuerSerial,
 id-aa-contentReference, ContentReference, id-aa-contentIdentifier,
 ContentIdentifier, id-aa-signingCertificateV2
    FROM 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) }

– Internet X.509 Public Key Infrastructure – Certificate and CRL Profile: RFC 3280

 Certificate, AlgorithmIdentifier, CertificateList, Name,
 Attribute
    FROM PKIX1Explicit88
    {iso(1) identified-organization(3) dod(6) internet(1)

Pinkas, et al. Informational [Page 77] RFC 5126 CMS Advanced Electronic Signatures February 2008

    security(5) mechanisms(5) pkix(7) id-mod(0)
    id-pkix1-explicit(18)}
 GeneralNames, GeneralName, PolicyInformation
    FROM PKIX1Implicit88 {iso(1) identified-organization(3) dod(6)
    internet(1) security(5) mechanisms(5) pkix(7) id-mod(0)
    id-pkix1-implicit(19)}

– Internet Attribute Certificate Profile for Authorization - RFC 3281

 AttributeCertificate
    FROM PKIXAttributeCertificate {iso(1) identified-organization(3)
    dod(6) internet(1) security(5) mechanisms(5) pkix(7) id-mod(0)
    id-mod-attribute-cert(12)}

– OCSP RFC 2560

 BasicOCSPResponse, ResponderID
    FROM OCSP {iso(1) identified-organization(3) dod(6) internet(1)
    security(5) mechanisms(5) pkix(7) id-mod(0) id-mod-ocsp(14)}

RFC 3161 Internet X.509 Public Key Infrastructure – Time-Stamp Protocol

 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)}

– X.520

  DirectoryString {}
      FROM SelectedAttributeTypes
       {joint-iso-itu-t ds(5) module(1) selectedAttributeTypes(5) 4}

;

– Definitions of Object Identifier arcs used in the present document –

– OID used referencing electronic signature mechanisms based – on the present document 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) }

Pinkas, et al. Informational [Page 78] RFC 5126 CMS Advanced Electronic Signatures February 2008

– Basic ES Attributes Defined in the present document –

CMS Attributes defined in the present document

– OtherSigningCertificate - deprecated

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 THE PRESENT DOCUMENT
 }
 OtherCertID ::= SEQUENCE {
    otherCertHash            OtherHash,
    issuerSerial             IssuerSerial OPTIONAL }
 OtherHash ::= CHOICE {
    sha1Hash OtherHashValue,
    -- This contains a SHA-1 hash
    otherHash OtherHashAlgAndValue}

– Policy ES Attributes Defined in the present document –

– Mandatory Basic Electronic Signature Attributes, plus in addition. – 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
                            -- not used in this version
 }
 SignaturePolicyId ::= SEQUENCE {
    sigPolicyId           SigPolicyId,
    sigPolicyHash         SigPolicyHash,
    sigPolicyQualifiers   SEQUENCE SIZE (1..MAX) OF
                               SigPolicyQualifierInfo OPTIONAL

Pinkas, et al. Informational [Page 79] RFC 5126 CMS Advanced Electronic Signatures February 2008

 }
 SignaturePolicyImplied ::= NULL
 SigPolicyId ::= OBJECT IDENTIFIER
 SigPolicyHash ::= OtherHashAlgAndValue
 OtherHashAlgAndValue ::= SEQUENCE {
    hashAlgorithm   AlgorithmIdentifier,
    hashValue       OtherHashValue
 }
 OtherHashValue ::= OCTET STRING
 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-spq-ets-unotice SIG-QUALIFIER-TYPE
    SPUserNotice }
 pointerToSigPolSpec SIG-POLICY-QUALIFIER ::= {
    SIG-POLICY-QUALIFIER-ID id-spq-ets-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 }

Pinkas, et al. Informational [Page 80] RFC 5126 CMS Advanced Electronic Signatures February 2008

 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}

Pinkas, et al. Informational [Page 81] RFC 5126 CMS Advanced Electronic Signatures February 2008

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 shall be present
    countryName [0] DirectoryString{maxSize} OPTIONAL,
       -- as used to name a Country in X.520
    localityName [1] DirectoryString{maxSize} OPTIONAL,
       -- as used to name a locality in X.520
    postalAdddress [2] PostalAddress OPTIONAL }
 PostalAddress ::= SEQUENCE SIZE(1..6) OF DirectoryString{maxSize}
                  -- maxSize parametrization as specified in X.683

– 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 RFC 3281: see Section 4.1

– 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

Pinkas, et al. Informational [Page 82] RFC 5126 CMS Advanced Electronic Signatures February 2008

– 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

– 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,

Pinkas, et al. Informational [Page 83] RFC 5126 CMS Advanced Electronic Signatures February 2008

     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      SEQUENCE OF OTHER-REVOCATION-REF.&Type
 }

OTHER-REVOCATION-REF ::= CLASS {

    &Type,
    &id   OBJECT IDENTIFIER UNIQUE }
 WITH SYNTAX {
    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 OPTIONAL
 }
 OtherRevVals ::= SEQUENCE {
    otherRevValType   OTHER-REVOCATION-VAL.&id,
    otherRevVals      SEQUENCE OF OTHER-REVOCATION-REF.&Type
 }
OTHER-REVOCATION-VAL ::= CLASS {
    &Type,

Pinkas, et al. Informational [Page 84] RFC 5126 CMS Advanced Electronic Signatures February 2008

    &id   OBJECT IDENTIFIER UNIQUE }
 WITH SYNTAX {
    WITH SYNTAX &Type ID &id }

– CAdES-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

– Archive Timestamp

id-aa-ets-archiveTimestampV2 OBJECT IDENTIFIER ::= { iso(1) member-body(2) us(840) rsadsi(113549) pkcs(1) pkcs-9(9) smime(16) id-aa(2) 48}

 ArchiveTimeStampToken ::= TimeStampToken

– Attribute certificate references

id-aa-ets-attrCertificateRefs OBJECT IDENTIFIER ::= { iso(1) member-body(2) us(840) rsadsi(113549) pkcs(1) pkcs-9(9) smime(16) id-aa(2) 44}

 AttributeCertificateRefs ::=  SEQUENCE OF OtherCertID

– Attribute revocation references

id-aa-ets-attrRevocationRefs OBJECT IDENTIFIER ::= { iso(1) member-body(2) us(840) rsadsi(113549) pkcs(1) pkcs-9(9) smime(16) id-aa(2) 45}

 AttributeRevocationRefs ::=  SEQUENCE OF CrlOcspRef

END

Pinkas, et al. Informational [Page 85] RFC 5126 CMS Advanced Electronic Signatures February 2008

Annex B (Informative): Extended Forms of Electronic Signatures

 Section 4 provides an overview of the various formats of electronic
 signatures included in the present document.  This annex lists the
 attributes that need to be present in the various extended electronic
 signature formats and provides example validation sequences using the
 extended formats.

B.1. Extended Forms of Validation Data

 The Complete validation data (CAdES-C) described in Section 4.3 and
 illustrated in Figure 3 may be extended to create electronic
 signatures with extended validation data.  Some electronic signature
 forms that include extended validation are explained below.
 An X-Long electronic signature (CAdES-X Long) is the CAdES-C with the
 values of the certificates and revocation information.
 This form of electronic signature can be useful when the verifier
 does not have direct access to the following information:
  1. the signer's certificate;
  1. all the CA certificates that make up the full certification

path;

  1. all the associated revocation status information, as referenced

in the CAdES-C.

 In some situations, additional time-stamps may be created and added
 to the Electronic Signatures as additional attributes.  For example:
  1. time-stamping all the validation data as held with the ES

(CAdES-C), this eXtended validation data is called a CAdES-X

      Type 1; or
  1. time-stamping individual reference data as used for complete

validation. This form of eXtended validation data is called an

      CAdES-X Type 2.
    NOTE 1: The advantages/drawbacks for CAdES-X Type 1 and CAdES-X
    Type 2 are discussed in Annex C.4.4.
 The above time-stamp forms can be useful when it is required to
 counter the risk that any CA keys used in the certificate chain may
 be compromised.

Pinkas, et al. Informational [Page 86] RFC 5126 CMS Advanced Electronic Signatures February 2008

 A combination of the two formats above may be used.  This form of
 eXtended validation data is called an ES X-Long Type 1 or CAdES-X
 Long Type 2.  This form of electronic signature can be useful when
 the verifier needs both the values and proof of when the validation
 data existed.
    NOTE 2: The advantages/drawbacks for CAdES-X long Type 1 and
    CAdES-X long Type 2 are discussed in Annex C.4.6.

B.1.1. CAdES-X Long

 An electronic signature with the additional validation data forming
 the CAdES-X Long form (CAdES-X-Long) is illustrated in Figure B.1 and
 comprises the following:
  1. CAdES-BES or CAdES-EPES, as defined in Sections 4.3 , 5.7, or

5.8;

  1. complete-certificate-references attribute, as defined in Section

6.2.1;

  1. complete-revocation-references attribute, as defined in Section

6.2.2.

 The following attributes are required if a TSP is not providing a
 time-mark of the ES:
  1. signature-time-stamp attribute, as defined in Section 6.1.1.
 The following attributes are required if the full certificate values
 and revocation values are not already included in the CAdES-BES or
 CAdES-EPES:
  1. certificate-values attribute, as defined in Section 6.3.3;
  1. revocation-values attribute, as defined in Section 6.3.4.
 If attributes certificates are used, then the following attributes
 may be present:
  1. attribute-certificate-references attribute, defined in Section

6.2.3;

  1. attribute-revocation-references attribute, as defined in Section

6.2.4.

 Other unsigned attributes may be present, but are not required.

Pinkas, et al. Informational [Page 87] RFC 5126 CMS Advanced Electronic Signatures February 2008

    NOTE: Attribute certificate and revocation references are only
    present if a user attribute certificate is present in the
    electronic signature; see Sections 6.2.2 and 6.2.3.

+———————- CAdES-X-Long ——————————–+

+————————————– CAdES-C —+
+———-+ +————-+
+—– CAdES-BES or CAdES-EPES —-+ Timestamp
over Complete
+———++———-++———+ digital certificate
signature and
Signer's Signed Digital revocation
Document Attributessignature Optional data
when
+———++———-++———+ timemarked
+———————————-+ +———-+
+———–+ +————-+
Complete
certificate
and
revocation
references
+———–+
+————————————————–+

+——————————————————————–+

           Figure B.1: Illustration of CAdES-X-Long

B.1.2. CAdES-X Type 1

 An electronic signature with the additional validation data forming
 the eXtended validation data - Type 1 X is illustrated in Figure B.2
 and comprises the following:
  1. the CAdES-BES or CAdES-EPES, as defined in Sections 4.2, 5.7, or

5.8;

  1. complete-certificate-references attribute, as defined in Section

6.2.1;

  1. complete-revocation-references attribute, as defined in Section

6.2.2;

  1. CAdES-C-Timestamp attribute, as defined in Section 6.3.5.

Pinkas, et al. Informational [Page 88] RFC 5126 CMS Advanced Electronic Signatures February 2008

 The following attributes are required if a TSP is not providing a
 time-mark of the ES:
  1. signature-time-stamp attribute, as defined in Section 6.1.1.
 If attributes certificates are used, then the following attributes
 may be present:
  1. attribute-certificate-references attribute, defined in Section

6.2.3;

  1. attribute-revocation-references attribute, as defined in Section

6.2.4.

 Other unsigned attributes may be present, but are not required.

+———————— CAdES-X-Type 1 —————————-+

+———————————- CAdES-C ——+
+———-+ +————-+
+— CAdES-BES or CAdES-EPES ——+Timestamp
over
+———++———-++———+digital
Signer's Signed Digital signature Timestamp
Document Attributessignature over
Optional CAdES-C
+———++———-++———+when
+———————————-+timemarked
+———-+
+———–+ +————-+
Complete
certificate
and
revocation
references
+———–+
+————————————————-+

+——————————————————————–+

             Figure B.2: Illustration of CAdES-X Type 1

Pinkas, et al. Informational [Page 89] RFC 5126 CMS Advanced Electronic Signatures February 2008

B.1.3. CAdES-X Type 2

 An electronic signature with the additional validation data forming
 the eXtended Validation Data - Type 2 X is illustrated in Figure B.3
 and comprises the following:
  1. CAdES-BES or CAdES-EPES, as defined in Sections 4.2, 5.7, or

5.8;

  1. complete-certificate-references attribute, as defined in Section

6.2.1;

  1. complete-revocation-references attribute, as defined in Section

6.2.2;

  1. time-stamped-certs-crls-references attribute, as defined in

Section 6.3.6.

 The following attributes are required if a TSP is not providing a
 time-mark of the ES:
  1. signature-time-stamp attribute, as defined in Section 6.1.1.
 If attributes certificates are used, then the following attributes
 may be present:
  1. attribute-certificate-references attribute, defined in Section

6.2.3;

  1. attribute-revocation-references attribute, as defined in Section

6.2.4.

 Other unsigned attributes may be present, but are not required.

Pinkas, et al. Informational [Page 90] RFC 5126 CMS Advanced Electronic Signatures February 2008

+———————– CAdES-X-Type 2 —————————–+

+————————————– CAdES-C –+
+———-+
+– CAdES-BES or CAdES-EPES ——-+Timestamp
over
+———++———-++———+digital +————-+
Signature Timestamp
Signer's Signed Digital only over
Document AttributessignatureOptional Complete
when certificate
+———++———-++———+Timemarked and
+———————————-++———-+ revocation
+———–+ references
Complete +————-+
certificate
and
revocation
references
+———–+
+————————————————-+

+——————————————————————–+

             Figure B.3: Illustration of CAdES-X Type 2

B.1.4. CAdES-X Long Type 1 and CAdES-X Long Type 2

 An electronic signature with the additional validation data forming
 the CAdES-X Long Type 1 and CAdES-X Long Type 2 is illustrated in
 Figure B.4 and comprises the following:
  1. CAdES-BES or CAdES-EPES, as defined in Sections 4.3, 5.7, or

5.8;

  1. complete-certificate-references attribute, as defined in Section

6.2.1;

  1. complete-revocation-references attribute, as defined in Section

6.2.2;

 The following attributes are required if a TSP is not providing a
 time-mark of the ES:
  1. signature-time-stamp attribute, as defined in Section 6.1.1.

Pinkas, et al. Informational [Page 91] RFC 5126 CMS Advanced Electronic Signatures February 2008

 The following attributes are required if the full certificate values
 and revocation values are not already included in the CAdES-BES or
 CAdES-EPES:
  1. certificate-values attribute, as defined in Section 6.3.3;
  1. revocation-values attribute, as defined in Section 6.3.4.
 If attributes certificates are used, then the following attributes
 may be present:
  1. attribute-certificate-references attribute, defined in Section

6.2.3;

  1. attribute-revocation-references attribute, as defined in Section

6.2.4.

 Plus one of the following attributes is required:
  1. CAdES-C-Timestamp attribute, as defined in Section 6.3.5;
  1. time-stamped-certs-crls-references attribute, as defined in

Section 6.3.6.

 Other unsigned attributes may be present, but are not required.

Pinkas, et al. Informational [Page 92] RFC 5126 CMS Advanced Electronic Signatures February 2008

 +---------------------- CAdES-X-Type 1 or 2 ------------------------+
 |                                                   +--------------+|
 |+-------------------------------------- CAdES-C --+|+------------+||
 ||                                    +----------+ ||| Timestamp  |||
 ||+-- CAdES-BES or CAdES-EPES -------+|Timestamp | |||    over    |||
 |||                                  ||over      | |||  CAdES-C   |||
 |||+---------++----------++---------+||digital   | | +------------+ |
 ||||         ||          ||         |||signature | ||      or      ||
 ||||Signer's ||  Signed  || Digital |||          | ||+------------+||
 ||||Document ||Attributes||Signature|||Optional  | ||| Timestamp  |||
 ||||         ||          ||         |||when      | ||| only over  |||
 |||+---------++----------++---------+||timemarked| ||| complete   |||
 ||+----------------------------------++----------+ ||| certificate|||
 ||                                                 |||    and     |||
 ||                                    +-----------+||| revocation |||
 ||                                    |Complete   |||| references |||
 ||                                    |certificate|||+------------+||
 ||                                    |and        ||+--------------+|
 ||                                    |revocation || +------------+ |
 ||                                    |references || |Complete    | |
 ||                                    +-----------+| |certificate | |
 |+-------------------------------------------------+ |   and      | |
 |                                                    |revocation  | |
 |                                                    |  values    | |
 |                                                    +------------+ |
 +-------------------------------------------------------------------+
           Figure B.4: Illustration of CAdES-X Long Type 1
                       and CAdES-X Long Type 2

B.2. Time-Stamp Extensions

 Each instance of the time-stamp attribute may include, as unsigned
 attributes in the signedData of the time-stamp, the following
 attributes related to the TSU:
  1. complete-certificate-references attribute of the TSU, as defined

in Section 6.2.1;

  1. complete-revocation-references attribute of the TSU, as defined

in Section 6.2.2;

  1. certificate-values attribute of the TSU, as defined in Section

6.3.3;

  1. revocation-values attribute of the TSU, as defined in Section

6.3.4.

Pinkas, et al. Informational [Page 93] RFC 5126 CMS Advanced Electronic Signatures February 2008

 Other unsigned attributes may be present, but are not required.

B.3. Archive Validation Data (CAdES-A)

 Before the algorithms, keys, and other cryptographic data used at the
 time the CAdES-C was built become weak and the cryptographic
 functions become vulnerable, or the certificates supporting previous
 time-stamps expire, the signed data, the CAdES-C, and any additional
 information (i.e., any CAdES-X) should be time-stamped.  If possible,
 this should use stronger algorithms (or longer key lengths) than in
 the original time-stamp.  This additional data and time-stamp is
 called Archive validation data required for the ES Archive format
 (CAdES-A).  The Time-stamping process may be repeated every time the
 protection used to time-stamp a previous CAdES-A becomes weak.  A
 CAdES-A may thus bear multiple embedded time-stamps.
 An example of an electronic signature (ES), with the additional
 validation data for the CAdES-C and CAdES-X forming the CAdES-A is
 illustrated in Figure B.5.

Pinkas, et al. Informational [Page 94] RFC 5126 CMS Advanced Electronic Signatures February 2008

+————————— CAdES-A———————————+

+—————————————————-+
+————–+ +———-+
+——————— CAdES-C —-++————+
+———-+ Timestamp
+– CAdES-BES ——+Timestamp over
or CAdES-EPES over CAdES-C Archive
digital +————+
signature or Timestamp
+————+
optional Timestamp
when only over
timemarked complete
+——————-++———-+ certificate +———-+
and
+————-+ revocation
Complete references
certificate +————+
and +————–+
revocation +————+
references Complete
+————-+ certificate
+———————————-+ and
revocation
values
+————+
+—————————————————-+

+——————————————————————–+

                  Figure B.5: Illustration of CAdES-A
 The CAdES-A comprises the following elements:
  1. the CAdES-BES or CAdES-EPES, including their signed and unsigned

attributes;

  1. complete-certificate-references attribute, as defined in Section

6.2.1;

  1. complete-revocation-references attribute, as defined in Section

6.2.2.

 The following attributes are required if a TSP is not providing a
 time-mark of the ES:
  1. signature-time-stamp attribute, as defined in Section 6.1.1.

Pinkas, et al. Informational [Page 95] RFC 5126 CMS Advanced Electronic Signatures February 2008

 If attributes certificates are used, then the following attributes
 may be present:
  1. attribute-certificate-references attribute, defined in Section

6.2.3;

  1. attribute-revocation-references attribute, as defined in Section

6.2.4.

 The following attributes are required if the full certificate values
 and revocation values are not already included in the CAdES-BES or
 CAdES-EPES:
  1. certificate-values attribute, as defined in Section 6.3.3;
  1. revocation-values attribute, as defined in Section 6.3.4.
 At least one of the following two attributes is required:
  1. CAdES-C-Timestamp attribute, as defined in Section 6.3.5;
  1. time-stamped-certs-crls-references attribute, as defined in

Section 6.3.6.

 The following attribute is required:
  1. archive-time-stamp attributes, defined in Section 6.4.1.
 Several instances of the archive-time-stamp attribute may occur with
 an electronic signature, both over time and from different TSUs.  The
 time-stamp should be created using stronger algorithms (or longer key
 lengths) than in the original electronic signatures or time-stamps.
 Other unsigned attributes of the ES may be present, but are not
 required.
 The archive-time-stamp will itself contain the certificate and
 revocation information required to validate the archive-time-stamp;
 this may include the following unsigned attributes:
  1. complete-certificate-references attribute of the TSU, as defined

in Section 6.2.1;

  1. complete-revocation-references attribute of the TSU, as defined

in Section 6.2.2;

  1. certificate-values attribute of the TSU, as defined in Section

6.3.3;

Pinkas, et al. Informational [Page 96] RFC 5126 CMS Advanced Electronic Signatures February 2008

  1. revocation-values attribute of the TSU, as defined in Section

6.3.4.

 Other unsigned attributes may be present, but are not required.

B.4. Example Validation Sequence

 As described earlier, the signer or initial verifier may collect all
 the additional data that forms the electronic signature.  Figure B.6
 and the subsequent description describe how the validation process
 may build up a complete electronic signature over time.

+—————————————— CAdES-C ————-+

+——————————- CAdES-T ——+
+————– CAdES ————+
+——————–++———++———+ +———–+
Timestamp Complete
Sign.Pol Digital over certificate
Id. Signed signaturedigital and
option.attributes signature revocation
+———++———+ references
+——————–+ +———–+
+———————————+
1 /
+———————- ————/——–+

+———————– | ———- / ————— / ——-+

                       |           /2    ----3--------
    +----------+       |          /     /
    |          |       v         /     |
    | Signer's |      +---------------------+     +-------------+
    | document |----->| Validation Process  |---->|- Valid      |
    |          |      +---------------------+ 4   |- Invalid    |
    +----------+           |  ^       |  ^        |- Validation |
                           v  |       v  |        |  Incomplete |
                       +---------+ +--------+     +-------------+
                       |Signature| |Trusted |
                       | Policy  | |Service |
                       | Issuer  | |Provider|
                       +---------+ +--------+
     Figure B.6: Illustration of a CAdES validation sequence
 Soon after receiving the electronic signature (CAdES) from the signer
 (1), the digital signature value may be checked; the validation
 process shall 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 using additional
 data (e.g., certificates, CRL, etc.) provided by Trusted Service

Pinkas, et al. Informational [Page 97] RFC 5126 CMS Advanced Electronic Signatures February 2008

 Providers.  When applicable, the validation process will also need to
 conform to the requirements specified in a signature policy.  If the
 validation process is validation incomplete, then the output from
 this stage is the CAdES-T.
 To ascertain the validity status as Valid or Invalid and communicate
 that to the user (4), all the additional data required to validate
 the CAdES-C must be available (e.g., the complete certificate and
 revocation information).
 Once the data needed to complete validation data references (CAdES-C)
 is available, then the validation process should:
  1. obtain all the necessary additional certificates and revocation

status information;

  1. complete all the validation checks on the ES using the complete

certificate and revocation information (if a time-stamp is not

      already present, this may be added at the same stage, combining
      the CAdES-T and CAdES-C processes);
  1. record the complete certificate and revocation references (3);
  1. indicate the validity status to the user (4).
 At the same time as the validation process creates the CAdES-C, the
 validation process may provide and/or record the values of
 certificates and revocation status information used in CAdES-C (5).
 The end result is called CAdES-X Long.
 This is illustrated in Figure B.7.

Pinkas, et al. Informational [Page 98] RFC 5126 CMS Advanced Electronic Signatures February 2008

+—————————————————– CAdES-X Long -+

+——————————- CAdES-C ————-+
+————– CAdES ————+
+——————–++———++———+ +———–+
Timestamp Complete
Sign.Pol Digital over certificate
Id. Signed signaturedigital and
option.attributes signature revocation
+———+ values
+——————–++———+ +———–++———–+
+———————————+ Complete
certificate
2 and
revocation
references
1 / +———–+
+———————— ——- / ——— —–+ /

+————————- | —— / ———- |——— / ——-+

                         |       /      ----- /  ------- /
    +----------+         |      /      /  3     /   5
    |          |         v     |      |        |
    | Signer's |      +--------------------+      +-----------+
    | document |----->| Validation Process |----->| - Valid   |
    |          |      +--------------------+  4   | - Invalid |
    +----------+          |  ^       |  ^         +-----------+
                          v  |       v  |
                      +---------+ +--------+
                      |Signature| |Trusted |
                      | Policy  | |Service |
                      | Issuer  | |Provider|
                      +---------+ +--------+
        Figure B.7: Illustration of a CAdES validation sequence
                    with CAdES-X Long
 When the validation process creates the CAdES-C, it may also create
 extended forms of validation data.
 A first alternative is to time-stamp all data forming the CAdES-X
 Type 1.
 This is illustrated in Figure B.8.

Pinkas, et al. Informational [Page 99] RFC 5126 CMS Advanced Electronic Signatures February 2008

+———————————————— CAdES-X Type 1 —–+

+——————————- CAdES-C ——————+
+————– CAdES ————+
+——————–++———++———++———-++——-+
Timestamp Complete
Sign.Pol Digital over cert. Time-
Id. Signed signaturedigital and stamp
option.attributes signature revoc. over
+———++———+referencesCAdES-C
+——————–+
+———————————+ +———-++——-+
1 /
+———————— ——— / ———– / —–+

+————————- | ——– / ———– / ——— / —-+

                         |       2 /     ---3----            /
    +----------+         |        /    /   -----------5------
    |          |         v       |    |  /
    | Signer's |      +--------------------+       +-----------+
    | document |----->| Validation Process |-----> | - Valid   |
    |          |      +--------------------+  4    | - Invalid |
    +----------+          |  ^       |  ^          +-----------+
                          v  |       v  |
                      +---------+ +--------+
                      |Signature| |Trusted |
                      | Policy  | |Service |
                      | Issuer  | |Provider|
                      +---------+ +--------+
  Figure B.8: Illustration of CAdES with eXtended validation data
              CAdES-X Type 1
 Another alternative is to time-stamp the certificate and revocation
 information references used to validate the electronic signature (but
 not the signature) (6).  The end result is called CAdES-X Type 2.
 This is illustrated in Figure B.9.

Pinkas, et al. Informational [Page 100] RFC 5126 CMS Advanced Electronic Signatures February 2008

+——————————————– CAdES-X Type 2 ——–+

+——————————- CAdES-C ————-+
+————– CAdES ————+
+——————–++———++———+ +———–+
Timestamp Timestamp
Sign.Pol over over
Id. Signed Digital digital complete
option.attributessignaturesignature certificate
+——————–++———++———+ and
+———————————+ +———–+revocation
Complete references
certificate+———–+
and
1 2 revocation
references
+———–+
+———————— ——— ——–+
3 /
/ ———-
/ / / 6
/ / /
/ / /

+————————- | —– | – | – / ———————-+

                         |       |    |   |
                         v       |    |   |
                      +--------------------+      +-----------+
                      | Validation Process |----->| - Valid   |
                      +--------------------+  4   | - Invalid |
                          |  ^       |  ^         +-----------+
                          v  |       v  |
                      +---------+ +--------+
                      |Signature| |Trusted |
                      | Policy  | |Service |
                      | Issuer  | |Provider|
                      +---------+ +--------+
 Figure B.9: Illustration of CAdES with eXtended validation data
             CAdES-X Type 2
 Before the algorithms used in any of the electronic signatures become
 or are likely to be compromised or rendered vulnerable in the future,
 it may be necessary to time-stamp the entire electronic signature,
 including all the values of the validation and user data as an ES
 with Archive validation data (CAdES-A) (7).
 A CAdES-A is illustrated in Figure B.10.

Pinkas, et al. Informational [Page 101] RFC 5126 CMS Advanced Electronic Signatures February 2008

+—————————– CAdES-A —————————+

+– CAdES-X Long Type 1 or 2 ———-+
+————+
Archive
Time-stamp
+————+
+—————————————+
+———-+
/
Signers' /
Document \ /
\ 1 2 3 5 6 7 /
+———-+ \ /
\ /

+—————– \ — | - | - | - | —— / ——————+

                  \    |   |   |   |       |
                   |   |   |   |   |       |
                   |   |   |   |   |       |
                   v   v   |   |   |       |
               +-----------------------------+      +-----------+
               |      Validation Process     |----->| - Valid   |
               +-----------------------------+  4   | - Invalid |
                   |  ^       |  ^                  +-----------+
                   v  |       v  |
               +---------+ +--------+
               |Signature| |Trusted |
               | Policy  | |Service |
               | Issuer  | |Provider|
               +---------+ +--------+
               Figure B.10: Illustration of CAdES-A

B.5. Additional Optional Features

 The present document also defines additional optional features to:
  1. indicate a commitment type being made by the signer;
  1. indicate the claimed time when the signature was done;
  1. indicate the claimed location of the signer;
  1. indicate the claimed or certified role under which a signature

was created;

Pinkas, et al. Informational [Page 102] RFC 5126 CMS Advanced Electronic Signatures February 2008

  1. support counter signatures;
  1. support multiple signatures.

Annex C (Informative): General Description

 This annex explains some of the concepts and provides the rationale
 for normative parts of the present document.
 The specification below includes a description of why and when each
 component of an electronic signature is useful, with a brief
 description of the vulnerabilities and threats and the manner by
 which they are countered.

C.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 need to be
 comprehensively defined and in a computer-processable form.
 The signature policy thus includes the following:
  1. rules that apply to technical validation of a particular

signature;

Pinkas, et al. Informational [Page 103] RFC 5126 CMS Advanced Electronic Signatures February 2008

  1. rules that 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);
  1. rules that 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.
 For example, the major rules required for technical validation can
 include:
  1. recognized root keys or "top-level certification authorities";
  1. acceptable certificate policies (if any);
  1. necessary certificate extensions and values (if any);
  1. the need for the revocation status for each component of the

certification tree;

  1. acceptable TSAs (if time-stamp tokens are being used);
  1. acceptable organizations for keeping the audit trails with

time-marks (if time-marking is being used);

  1. acceptable AAs (if any are being used),and;
  1. rules defining the components of the electronic signature that

shall be provided by the signer with data required by the

      verifier when required to provide long-term proof.

C.2. Signed Information

 The information being signed may be defined as a MIME-encapsulated
 message that 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 data, free text, or fields from an electronic form
 (e-form).  For example, the Adobe(tm) format "pdf" or the eXtensible
 Mark up Language (XML) may be used.  Annex D defines how the content
 may be structured to indicate the type of signed data using MIME.

C.3. Components of an Electronic Signature

C.3.1. Reference to the Signature Policy

 When two independent parties want to evaluate an electronic
 signature, it is fundamental that they get the same result.  This
 requirement can be met using comprehensive signature policies that

Pinkas, et al. Informational [Page 104] RFC 5126 CMS Advanced Electronic Signatures February 2008

 ensure consistency of signature validation.  Signature policies can
 be identified implicitly by the data being signed, or they can be
 explicitly identified using the CAdES-EPES form of electronic
 signature; the CAdES-EPES mandates a consistent signature policy must
 be used by both the signer and verifier.
 By signing over the Signature Policy Identifier in the CAdES-EPES,
 the signer explicitly indicates that he or she has applied the
 signature policy in creating the signature.
 In order to unambiguously identify the details of an explicit
 signature policy that is to be used to verify a CAdES-EPES, 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.
 In order to unambiguously identify the authority responsible for
 defining an explicit signature policy, the "Signature policy" can be
 signed.

C.3.2. Commitment Type Indication

 The commitment type can be indicated in the electronic signature
 either:
  1. explicitly using a "commitment type indication" in the

electronic signature;

  1. 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 type indications may be
 subject to signer and verifier agreement, specified as part of the
 signature policy or registered for generic use across multiple
 policies.
 If a CAdES-EPES electronic signature format is used and the
 electronic signature includes a commitment type indication other than
 one of those recognized under the signature policy, the signature
 shall be treated as invalid.
 How commitment is indicated using the semantics of the data being
 signed is outside the scope of the present document.

Pinkas, et al. Informational [Page 105] RFC 5126 CMS Advanced Electronic Signatures February 2008

    NOTE: Examples of commitment indicated through the semantics of
    the data being signed are:
  1. 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);
  1. an implicit commitment that 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).

C.3.3. Certificate Identifier from the Signer

 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
 citizen of a nation 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 that
 multiple private keys are used, 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 vulnerable to substitution attacks.  If the certificate
 from the signer was simply appended to the signature and thus not
 protected by the signature, anyone could substitute one certificate
 for another, and the message would appear to be signed by someone
 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.
 In order to unambiguously identify the certificate to be used for the
 verification of the signature, an identifier of the certificate from
 the signer shall be part of the signed data.

C.3.4. Role Attributes

 While the name of the signer is important, the position of the signer
 within a company or an organization is of paramount importance as
 well.  Some information (i.e., a contract) may only be valid if
 signed by a user in a particular role, e.g., a Sales Director.  In

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 many cases, who 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.
 The present document defines two different ways for providing this
 feature:
  1. by placing a claimed role name in the CMS signed attributes

field;

  1. by placing an 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 identity
    certificate.  However, it was decided not to follow this approach
    as it significantly complicates the management of certificates.
    For example, by using separate certificates for the signer's
    identity and roles means new identity keys need not be issued if a
    user's role changes.

C.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.

C.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,
 in most cases, might be 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 be
 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 unambiguously identify the attribute certificate(s) to be
 used for the verification of the signature, an identifier of the
 attribute certificate(s) from the signer shall be part of the signed
 data.

C.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 shall 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.

C.3.6. Signing Time

 The present document provides the capability to include a claimed
 signing time as an attribute of an electronic signature.
 Using this attribute, a signer may sign over a time that is the
 claimed signing time.  When an ES with Time is created (CAdES-T),
 then either a trusted time-stamp is obtained and added to the ES or a
 trusted time-mark exists in an audit trail.  When a verifier accepts
 a signature, the two times shall be within acceptable limits.
 A further optional attribute is defined in the present document to
 time-stamp the content and to provide proof of the existence of the
 content, at the time indicated by the time-stamp token.
 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 online 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 Section 5.11.4).

C.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 when data (as opposed to data that has been further signed or
 encrypted) is encapsulated in the SignedData (indicated by the

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 eContentType within EncapsulatedContentInfo being set to id-data),
 further typing information should be used to identify the type of
 document being signed.  This is generally achieved using the MIME
 content typing and encoding mechanism defined in RFC 2045 [6]).
 Further information on the use of MIME is given in Annex F.

C.3.8. content-hints

 The contents-hints attribute provides information on the innermost
 signed content of a multi-layer message where one content is
 encapsulated in another.  This may be useful if the signed data is
 itself encrypted.

C.3.9. Content Cross-Referencing

 When presenting a signed data is in relation to another signed data,
 it may be important to identify the signed data to which it relates.
 The content-reference and content-identifier attributes, as defined
 in ESS (RFC 2634 [5]), provide the ability to link a request and
 reply messages in an exchange between two parties.

C.4. Components of Validation Data

C.4.1. Revocation Status Information

 A verifier will have to ascertain that the certificate of the signer
 was valid at the time of the signature.  This can be done by either:
  1. using Certificate Revocation Lists (CRLs);
  1. using responses from an online certificate status server (for

example, obtained through the OCSP protocol).

    NOTE 1: The time of the signature may not be known, so
    time-stamping or time-marking may be used to provide the time
    indication of when it was known that the signature existed.
    NOTE 2: When validating an electronic signature and checking
    revocation status information, if a "grace period" is required, it
    needs to be suitably long enough to allow the involved authority
    to process a "last-minute" revocation request and for the request
    to propagate through the revocation system.  This grace period is
    to be added to the time included with the time-stamp token or the
    time-mark, and thus the revocation status information should be
    captured after the end of the grace period.

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C.4.1.1. 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.  However, a "grace period" is required to allow CAs time
 to process revocation requests.
 For example, a revocation request may arrive at a CA just before
 issuing the next CRL, and there may not enough time to include the
 revised revocation status information.  This involves checking that
 the signer certificate serial number is not included in the CRL.
 Either the signer, the initial verifier, or a subsequent verifier may
 obtain this CRL.  If obtained by the signer, then it shall 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 as a CAdES-C
 form.
 Even if the certificate serial number appears in the CRL with the
 status "suspended" (i.e., on hold), the signature is not to be deemed
 as valid since a suspended certificate is not supposed to be used
 even by its rightful owner.

C.4.1.2. 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, still providing a "grace period" suitable enough to allow
 the involved authority to process a "last-minute" revocation request.
 The signer, the verifier, or any other third party may fetch this
 OCSP response.  Since OCSP 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 so that they can
 then be easily retrieved and incorporate references to them in the
 electronic signature itself as a CAdES-C form.

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 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 same comment as for the CRL
 applies.

C.4.2. Certification Path

 A verifier may have to ascertain that the certification path was
 valid, at the time of the signature, up to a trust point, according
 to the:
  1. naming constraints;
  2. certificate policy constraints;
  3. signature policy, when applicable.
 Since the time of the signature cannot be known with certainty, an
 upper limit of it should be used as indicated by either the
 time-stamp or time-mark.
 In this case, 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; when applicable, this may be specified as part of the Signature
 Policy.  In addition, it will be necessary to capture the Certificate
 Authority Revocation Lists (CARLs) to prove that none of the CAs from
 the chain were revoked at the time of the signature.  Again, all this
 material may be incorporated in the electronic signature (ES X
 forms).  An alternative would be to store this information so that it
 can be easily retrieved and incorporate references to it in the
 electronic signature itself as a CAdES-C form.

C.4.3. Time-Stamping for Long Life of Signatures

 An important property for long-standing signatures is that a
 signature, having been found once to be valid, shall 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 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 the signer's certificate and all the
 CA certificates used to form a valid certification path were not
 revoked when the signature was created or verified.

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 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 were
 valid at 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 shall
 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 had been created before the certificate 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.
 Any time-stamp or time-mark that is taken after the expiration date
 of any certificate in the certification path has no value in proving
 the validity of a signature.
 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 Basic Electronic Signature,
 but it is the essential component of the ES with Time.
 It is required, in the present document, that if a signer's digital
 signature value is to be time-stamped, the time-stamp token is issued
 by a trusted source, known as a Time-Stamping Authority.
 The present document requires that the signer's digital signature
 value be time-stamped by a trusted source before the electronic
 signature can become an ES with Complete validation data.  Acceptable
 TSAs may be specified in a Signature Validation Policy.
 This technique is referred to as CAdES-C in the present document.

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 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.

C.4.4. Time-Stamping for Long Life of Signature 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 at 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 present document defines two ways of using time-stamps to protect
 against this compromise:
  1. time-stamp the ES with Complete validation data, when an OCSP

response is used to get the status of the certificate from the

      signer (CAdES-X Type 1).  This format is suitable to be used
      with an OCSP response, and it offers the additional advantage of
      providing an integrity protection over the whole data;
  1. 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 (CAdES-X Type2).  This format is
      suitable to be used with CRLs, since the time-stamped
      information may be used for more than one signature (when
      signers have their certificates issued by the same CA and when
      signatures can be checked using the same CRLs).
    NOTE: The signer, verifier, or both may obtain the time-stamp.

C.4.4.1. Time-Stamping the ES with Complete Validation Data (CAdES-X

        Type 1)
 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 revocation
 information references, which include the OCSP response, the
 time-stamp is placed on the CAdES-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

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 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 CAdES-X Type 1 in the present
 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 CAdES-X Long Type 1, as defined by the present document.
 A CAdES-X Long Type 1 is simply the concatenation of a CAdES-X Type
 1, with a copy of the additional data being referenced.

C.4.4.2. Time-Stamping Certificates and Revocation Information

        References (CAdES-X Type 2)
 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 exist 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 that could be claimed to exist
 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 be reduced to just one time-stamp per day (i.e., in

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 the case where 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.
 This technique is referred to as CAdES-X Type 2 in the present
 document and requires the following:
  1. all the CA certificates references and revocation information

references (i.e., CRLs) used in validating the CAdES-C are

      covered by one or more time-stamps.
 Thus, a CAdES-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+.

C.4.5. Time-Stamping for Archive 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 possibility.
 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 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 matters, a single technique called Archive
 validation data, covering all the cases, is being used in the present
 document.
 Archive validation data consists of the 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 the Archived Electronic Signature
 are required.
 The potential for a 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

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 before either the compromise of the signing key or 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 the
 present document was at least 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.
 This technique is referred to as CAdES-A in the present document.

C.4.6. Reference to Additional Data

 Using CAdES-X Type 1 or CAdES-X Type 2 extended validation data,
 verifiers still need 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 (CAdES-C) is adequate.  The actual certificates and
 CRL information reference in the CAdES-C can be gathered when needed
 for arbitration.
 If references to additional data are not adequate, then the actual
 values of all the certificates and revocation information required
 may be part of the electronic signature.  This technique is referred
 to as CAdES-X Long Type 1 or CAdES-X Long Type 2 in the present
 document.

C.4.7. 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:
  1. under the terms of the contract, a predefined common

"trusted" TSA may be used;

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  1. 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
 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 be 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 described above be used.
 This may be part of a mutually agreed Signature Validation Policy
 that is part of an agreed signature policy under which digital
 signatures may be used to support the business relationship between
 the two parties.

C.4.8. TSA Key Compromise

 TSA servers should be built in such a way that once the private
 signature key is installed, there is minimal likelihood of compromise
 over as long as a possible period.  Thus, the validity period for the
 TSA's keys should be as long as possible.
 Both the CAdES-T and the CAdES-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 CAdES-A should be used.  For extremely long
 periods, this may be applied repeatedly using new TSA keys.
 This technique is referred to as a nested CAdES-A in the present
 document.

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C.5. Multiple Signatures

 Some electronic signatures may only be valid if they bear more than
 one signature.  This is generally the case 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:
  1. independent signatures;
  2. 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 shall be provided.
 Embedded signatures are applied one after the other and are used
 where the order in which the signatures are applied is important.
 The capability to sign over signed data shall be provided.
 These forms are described in Section 5.13.  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 occurrences of the above two cases.

Annex D (Informative): Data Protocols to Interoperate with TSPs

D.1. Operational Protocols

 The following protocols can be used by signers and verifiers to
 interoperate with Trusted Service Providers during the electronic
 signature creation and validation.

D.1.1. Certificate Retrieval

 User certificates, CA certificates, and cross-certificates can be
 retrieved from a repository using the Lightweight Directory Access
 Protocol as defined in RFC 3494 [RFC3494], with the schema defined in
 RFC 4523 [RFC4523].

D.1.2. CRL Retrieval

 Certificate revocation lists, including authority revocation lists
 and partial CRL variants, can be retrieved from a repository using
 the Lightweight Directory Access Protocol, as defined in RFC 3494
 [RFC3494], with the schema defined in RFC 4523 [RFC4523].

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D.1.3. Online Certificate Status

 As an alternative to the use of certificate revocation lists, the
 status of a certificate can be checked using the Online Certificate
 Status Protocol (OCSP), as defined in RFC 2560 [3].

D.1.4. Time-Stamping

 The time-stamping service can be accessed using the Time-Stamping
 Protocol defined in RFC 3161 [7].

D.2. Management Protocols

 Signers and verifiers can use the following management protocols to
 manage the use of certificates.

D.2.1. Request for Certificate Revocation

 Request for a certificate to be revoked can be made using the
 revocation request and response messages defined in RFC 4210
 [RFC4210].

Annex E (Informative): Security Considerations

E.1. Protection of Private Key

 The security of the electronic signature mechanism defined in the
 present document depends on the privacy of the signer's private key.
 Implementations should take steps to ensure that private keys cannot
 be compromised.

E.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.

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Annex F (Informative): Example Structured Contents and MIME

F.1. Use of MIME to Encode Data

 The signed content may be structured using MIME (Multipurpose
 Internet Mail Extensions -- RFC 2045 [6]).  Whilst the MIME structure
 was initially developed for Internet email, it has a number of
 features that make it useful to provide a common structure for
 encoding a range of electronic documents and other multi-media data
 (e.g., photographs, video).  These features include:
  1. providing a means of signalling the type of "object" being

carried (e.g., text, image, ZIP file, application data);

  1. providing a means of associating a file name with an object;
  1. associating several independent objects (e.g., a document and

image) to form a multi-part object;

  1. handling data encoded in text or binary and, if necessary,

re-encoding the binary as text.

 When encoding a single object, MIME consists of:
  1. header information, followed by;
  1. encoded content.
 This structure can be extended to support multi-part content.

F.1.1. Header Information

 A MIME header includes:
 MIME Version information: e.g., MIME-Version: 1.0
 Content type information, which includes information describing the
 content sufficient for it to be presented to a user or application
 process, as required.  This includes information on the "media type"
 (e.g., text, image, audio) or whether the data is for passing to a
 particular type of application.  In the case of text, the content
 type includes information on the character set used, e.g.,
 Content-Type: text/plain; charset="us-ascii".
 Content-encoding information, which defines how the content is
 encoded (see below about encoding supported by MIME).

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 Other information about the content, such as a description or an
 associated file name.
 An example MIME header for text object is:
 Mime-Version: 1.0
 Content-Type: text/plain; charset=ISO-8859-1
 Content-Transfer-Encoding: quoted-printable
 An example MIME header for a binary file containing a pdf document
 is:
 Content-Type: application/pdf
 Content-Transfer-Encoding: base64
 Content-Description: JCFV201.pdf
 Content-Disposition: filename="JCFV201.pdf"

F.1.2. Content Encoding

 MIME supports a range of mechanisms for encoding both text and binary
 data.
 Text data can be carried transparently as lines of text data encoded
 in 7- or 8-bit ASCII characters.  MIME also includes a
 "quoted-printable" encoding that converts characters other than the
 basic ASCII into an ASCII sequence.
 Binary can either be carried:
  1. transparently as 8-bit octets; or
  1. converted to a basic set of characters using a system called

Base64.

    NOTE: As there are some mail relays that can only handle 7-bit
    ASCII, Base64 encoding is usually used on the Internet.

F.1.3. Multi-Part Content

 Several objects (e.g., text and a file attachment) can be associated
 together using a special "multi-part" content type.  This is
 indicated by the content type "multipart" with an indication of the
 string to be used indicating a separation between each part.
 In addition to a header for the overall multipart content, each part
 includes its own header information indicating the inner content type
 and encoding.

Pinkas, et al. Informational [Page 121] RFC 5126 CMS Advanced Electronic Signatures February 2008

 An example of a multipart content is:

Mime-Version: 1.0 Content-Type: multipart/mixed; boundary="—- =_NextPart_000_01BC4599.98004A80" Content-Transfer-Encoding: 7bit

——=_NextPart_000_01BC4599.98004A80 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit

Per your request, I've attached our proposal for the Java Card Version 2.0 API and the Java Card FAQ.

——=_NextPart_000_01BC4599.98004A80 Content-Type: application/pdf; name="JCFV201.pdf" Content-Transfer-Encoding: base64 Content-Description: JCFV201.pdf Content-Disposition: attachment; filename="JCFV201.pdf"

0M8R4KGxGuEAAAAAAAAAAAAAAAAAAAAAPgADAP7/CQAGAAAAAAAAAAAAAAACAAAAAgAAAAA AAAAAEAAAtAAAAAEAAAD+AAAAAAMAAAAGAAAA AANhAAQAYg==

——=_NextPart_000_01BC4599.98004A80–

 Multipart content can be nested.  So a set of associated objects
 (e.g., HTML text and images) can be handled as a single attachment to
 another object (e.g., text).
 The Content-Type from each part of the S/MIME message indicates the
 type of content.

F.2. S/MIME

 The specific use of MIME to carry CMS (extended as defined in the
 present document) secured data is called S/MIME (see [RFC3851]).
 S/MIME carries electronic signatures as either:
  1. an "application/pkcs7-mime" object with the CMS carried as a

binary attachment (PKCS7 is the name of the early version of

      CMS).
      The signed data may be included in the SignedData, which itself
      may be included in a single S/MIME object.  See [RFC3851],
      Section 3.4.2: "Signing Using application/pkcs7-mime with
      SignedData" and Figure F.1 hereafter.

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 or
  1. a "multipart/signed" object with the signed data and the

signature encoded as separate MIME objects.

      The signed data is not included in the SignedData, and the CMS
      structure only includes the signature.  See [RFC3851], Section
      3.4.3: "Signing Using the multipart/signed Format" and Figure
      F.2 hereafter.
      +-------------++----------++-------------++------------+
      |             ||          ||             ||            |
      |   S/MIME    ||  CAdES   ||    MIME     ||  pdf file  |
      |             ||          ||             ||            |
      |Content-Type=||SignedData||Content-Type=||Dear MrSmith|
      |application/ || eContent ||application/ ||Received    |
      |pkcs7-mime   ||          ||pdf          ||  100 tins  |
      |             ||          ||             ||            |
      |smime-type=  ||     /|   ||       /|    ||  Mr.Jones  |
      |signed-data  ||    / -----+      / ------+            |
      |             ||    \ -----+      \ ------+            |
      |             ||     \|   ||       \|    |+------------+
      |             ||          |+-------------+
      |             |+----------+
      +-------------+
          Figure F.1: Signing Using application/pkcs7-mime

F.2.1. Using application/pkcs7-mime

 This approach is similar to handling signed data as any other binary
 file attachment.
 An example of signed data encoded using this approach is:
 Content-Type: application/pkcs7-mime; smime-type=signed-data;
 Content-Transfer-Encoding: base64
 Content-Disposition: attachment; filename=smime.p7m
   567GhIGfHfYT6ghyHhHUujpfyF4f8HHGTrfvhJhjH776tbB9HG4VQbnj7
   77n8HHGT9HG4VQpfyF467GhIGfHfYT6rfvbnj756tbBghyHhHUujhJhjH
   HUujhJh4VQpfyF467GhIGfHfYGTrfvbnjT6jH7756tbB9H7n8HHGghyHh
   6YT64V0GhIGfHfQbnj75

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F.2.2. Using application/pkcs7-signature

 CMS also supports an alternative structure where the signature and
 data being protected are separate MIME objects carried within a
 single message.  In this case, the signed data is not included in the
 SignedData, and the CMS structure only includes the signature.  See
 [RFC3851], Section 3.4.3: "Signing Using the multipart/signed Format"
 and Figure F.2 hereafter.
 An example of signed data encoded using this approach is:
 Content-Type: multipart/signed;
           protocol="application/pkcs7-signature";
           micalg=sha1; boundary=boundary42
  1. -boundary42

Content-Type: text/plain

        This is a clear-signed message.
  1. -boundary42
 Content-Type: application/pkcs7-signature; name=smime.p7s
        Content-Transfer-Encoding: base64
        Content-Disposition: attachment; filename=smime.p7s
        ghyHhHUujhJhjH77n8HHGTrfvbnj756tbB9HG4VQpfyF467GhIGfHfYT6
        4VQpfyF467GhIGfHfYT6jH77n8HHGghyHhHUujhJh756tbB9HGTrfvbnj
        n8HHGTrfvhJhjH776tbB9HG4VQbnj7567GhIGfHfYT6ghyHhHUujpfyF4
        7GhIGfHfYT64VQbnj756
  1. -boundary42–
 With this second approach, the signed data passes through the CMS
 process and is carried as part of a multiple-parts signed MIME
 structure, as illustrated in Figure F.2.  The CMS structure just
 holds the electronic signature.

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 +---------------++----------++-------------++------------+
 |               ||          ||             ||            |
 |     MIME      ||  CAdES   ||    MIME     ||  pdf file  |
 |               ||          ||             ||            |
 |Content-Type=  ||SignedData||Content-Type=||Dear MrSmith|
 |multipart/     ||          ||application/ ||Received    |
 |signed         ||          ||pdf          ||  100 tins  |
 |        /|     ||          ||             ||            |
 |       / -------------------+        /|   ||  Mr.Jones  |
 |       \ -------------------+       / -----+            |
 |        \|     ||          ||       \ -----+            |
 |Content-Type=  ||          ||        \|   |+------------+
 |application/   ||          |+-------------+
 |pdf            ||          |
 |               ||          |
 |Content-Type=  ||          |
 |application/   ||          |
 |pkcs7-signature||          |
 |               ||          |
 |        /|     ||          |
 |       / -------+          |
 |       \ -------+          |
 |        \|     ||----------+
 |               |
 +---------------+
     Figure F.2: Signing Using application/pkcs7-signature
 This second approach (multipart/signed) has the advantage that the
 signed data can be decoded by any MIME-compatible system even if it
 does not recognize CMS-encoded electronic signatures.

Annex G (Informative): Relationship to the European Directive and EESSI

G.1. Introduction

 This annex provides an indication of the relationship between
 electronic signatures created under the present document and
 requirements under the European Parliament and Council Directive on a
 Community framework for electronic signatures.
    NOTE: Legal advice should be sought on the specific national
    legislation regarding use of electronic signatures.
 The present document is one of a set of standards that has been
 defined under the "European Electronic Signature Standardization
 Initiative" (EESSI) for electronic signature products and solutions
 compliant with the European Directive for Electronic Signatures.

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G.2. Electronic Signatures and the Directive

 This directive defines electronic signatures as:
  1. "data in electronic form which are attached to or logically

associated with other electronic data and which serve as a

      method of authentication".
 The directive states that an electronic signature should not be
 denied "legal effectiveness and admissibility as evidence in legal
 proceedings" solely on the grounds that it is in electronic form.
 The directive identifies an electronic signature as having
 equivalence to a hand-written signature if it meets specific
 criteria:
  1. it is an "advanced electronic signature" with the following

properties:

       a) it is uniquely linked to the signatory;
       b) it is capable of identifying the signatory;
       c) it is created using means that the signatory can maintain
          under his sole control; and
       d) it is linked to the data to which it relates in such a
          manner that any subsequent change of the data is detectable.
  1. it is based on a certificate that meets detailed criteria given

in Annex I of the directive and is issued by a

      "certification-service-provider" that meets requirements given
      in Annex II of the directive.  Such a certificate is referred to
      as a "qualified certificate";
  1. it is created by a "device", for which detailed criteria are

given in Annex III of the directive. Such a device is referred

      to a "secure-signature-creation device".
 This form of electronic signature is referred to as a "qualified
 electronic signature" in EESSI (see below).

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G.3. ETSI Electronic Signature Formats and the Directive

 An electronic signature created in accordance with the present
 document is:
    a) considered to be an "electronic signature" under the terms of
       the Directive;
    b) considered to be an "advanced electronic signature" under the
       terms of the Directive;
    c) considered to be a "Qualified Electronic Signature", provided
       the additional requirements in Annex I, II, and III of the
       Directive are met.  The requirements in Annex I, II, and III of
       the Directive are outside the scope of the present document,
       and are subject to standardization elsewhere.

G.4. EESSI Standards and Classes of Electronic Signature

G.4.1. Structure of EESSI Standardization

 EESSI looks at standards in several areas.  See the ETSI and CEN web
 sites for the latest list of standards and their versions:
  1. use of X.509 public key certificates as qualified certificates;
  1. security Management and Certificate Policy for CSPs Issuing

Qualified Certificates;

  1. security requirements for trustworthy systems used by CSPs

Issuing Qualified Certificates;

  1. security requirements for Secure Signature Creation Devices;
  1. security requirements for Signature Creation Systems;
  1. procedures for Electronic Signature Verification;
  1. electronic signature syntax and encoding formats;
  1. protocol to interoperate with a Time-Stamping Authority;
  1. Policy requirements for Time-Stamping Authorities; and
  1. XML electronic signature formats.

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 Each of these standards addresses a range of requirements, including
 the requirements of Qualified Electronic Signatures, as specified in
 Article 5.1 of the Directive.  However, some of them also address
 general requirements of electronic signatures for business and
 electronic commerce, which all fall into the category of Article 5.2
 of the Directive.  Such variation in the requirements may be
 identified either as different levels or different options.

G.4.2. Classes of Electronic Signatures

 Since some of these standards address a range of requirements, it may
 be useful to identify a set of standards to address a specific
 business need.  Such a set of standards and their uses define a class
 of electronic signature.  The first class already identified is the
 qualified electronic signature, fulfilling the requirements of
 Article 5.1 of the Directive.
 A limited number of "classes of electronic signatures" and
 corresponding profiles could be defined in close cooperation with
 actors on the market (business, users, suppliers). The need for such
 standards is envisaged, in addition to those for qualified electronic
 signatures, in areas such as:
  1. different classes of electronic signatures with long-term

validity;

  1. electronic signatures for business transactions with limited

value.

G.4.3. Electronic Signature Classes and the ETSI Electronic Signature

      Format
 The electronic signature format defined in the present document is
 applicable to the EESSI area "electronic signature and encoding
 formats".
 An electronic signature produced by a signer (see Section 5 and
 conformance Section 10.1) is applicable to the proposed class of
 electronic signature: "qualified electronic signatures fulfilling
 article 5.1".
 With the addition of attributes by the verifier (see Section 6 and
 conformance Section 10.2) the qualified electronic signature supports
 long-term validity.

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Annex H (Informative): APIs for the Generation and Verification of

                     Electronic Signatures Tokens
 While the present document describes the data format of an electronic
 signature, the question is whether there exist APIs (Application
 Programming Interfaces) able to manipulate these structures.  At
 least two such APIs have been defined; one set by the IETF and
 another set by the OMG (Object Management Group).

H.1. Data Framing

 In order to be able to use either of these APIs, it will be necessary
 to frame the previously defined electronic signature data structures
 using a mechanism-independent token format.  Section 3.1 of RFC 2743
 [RFC2743] specifies a mechanism-independent level of encapsulating
 representation for the initial token of a GSS-API context
 establishment sequence, incorporating an identifier of the mechanism
 type to be used on that context and enabling tokens to be interpreted
 unabmiguously.
 In order to be processable by these APIs, all electronic signature
 data formats that are defined in the present document shall be framed
 following that description.
 The encoding format for the token tag is derived from ASN.1 and DER,
 but its concrete representation is defined directly in terms of
 octets rather than at the ASN.1 level, in order to facilitate
 interoperable implementation without use of general ASN.1 processing
 code.  The token tag consists of the following elements, in order:
    1) 0x60 -- Tag for RFC 2743 SEQUENCE; indicates that constructed
       form, definite length encoding follows.
    2) Token-length octets, specifying length of subsequent data
       (i.e., the summed lengths of elements 3 to 5 in this list, and
       of the mechanism-defined token object following the tag).  This
       element comprises a variable number of octets:
       a) If the indicated value is less than 128, it shall be
          represented in a single octet with bit 8 (high order) set to
          "0" and the remaining bits representing the value.

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       b) If the indicated value is 128 or more, it shall be
          represented in two or more octets, with bit 8 of the first
          octet set to "1" and the remaining bits of the first octet
          specifying the number of additional octets.  The subsequent
          octets carry the value, 8 bits per octet, with the most
          significant digit first.  The minimum number of octets shall
          be used to encode the length (i.e., no octets representing
          leading zeros shall be included within the length encoding).
    3) 0x06 -- Tag for OBJECT IDENTIFIER.
    4) Object identifier length -- length (number of octets) of the
       encoded object identifier contained in element 5, encoded per
       rules as described in 2a) and 2b) above.
    5) object identifier octets -- variable number of octets, encoded
       per ASN.1 BER rules:
  1. The first octet contains the sum of two values:
          (1) the top-level object identifier component, multiplied by
              40 (decimal); and
          (2) the second-level object identifier component.
              This special case is the only point within an object
              identifier encoding where a single octet represents
              contents of more than one component.
  1. Subsequent octets, if required, encode successively lower

components in the represented object identifier. A

            component's encoding may span multiple octets, encoding 7
            bits per octet (most significant bits first) and with bit
            8 set to "1" on all but the final octet in the component's
            encoding.  The minimum number of octets shall be used to
            encode each component (i.e., no octets representing
            leading zeros shall be included within a component's
            encoding).
    NOTE: In many implementations, elements 3 to 5 may be stored and
    referenced as a contiguous string constant.
 The token tag is immediately followed by a mechanism-defined token
 object.  Note that no independent size specifier intervenes following
 the object identifier value to indicate the size of the
 mechanism-defined token object.

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 Tokens conforming to the present document shall have the following
 OID in order to be processable by IDUP-APIs:
 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) }

H.2. IDUP-GSS-APIs Defined by the IETF

 The IETF CAT WG produced, in December 1998, an RFC (RFC 2479
 [RFC2479]) under the name of IDUP-GSS-API (Independent Data Unit
 Protection) able to handle the electronic signature data format
 defined in the present document.
 The IDUP-GSS-API includes support for non-repudiation services.
 It supports evidence generation, where "evidence" is information that
 either by itself, or when used in conjunction with other information,
 is used to establish proof about an event or action, as well as
 evidence verification.
 IDUP supports various types of evidences.  All the types defined in
 IDUP are supported in the present document through the
 commitment-type parameter.
 Section 2.3.3 of IDUP describes the specific calls needed to handle
 evidence ("EV" calls).  The "EV" group of calls provides a simple,
 high-level interface to underlying IDUP mechanisms when application
 developers need to deal with only evidence: not with encryption or
 integrity services.
 All generations and verification are performed according to the
 content of a NR policy that is referenced in the context.
 Get_token_details is used to return the attributes that correspond to
 a given input token to an application.  Since IDUP-GSS-API tokens are
 meant to be opaque to the calling application, this function allows
 the application to determine information about the token without
 having to violate the opaqueness intention of IDUP.  Of primary
 importance is the mechanism type, which the application can then use
 as input to the IDUP_Establish_Env() call in order to establish the
 correct environment in which to have the token processed.
 Generate_token generates a non-repudiation token using the current
 environment.

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 Verify_evidence verifies the evidence token using the current
 environment.  This operation returns a major_status code that can be
 used to determine whether the evidence contained in a token is
 complete (i.e., can be successfully verified (perhaps years) later).
 If a token's evidence is not complete, the token can be passed to
 another API, form_complete_pidu, to complete it.  This happens when a
 status "conditionally valid" is returned.  That status corresponds to
 the status "validation incomplete" of the present document.
 Form_complete_PIDU is used primarily when the evidence token itself
 does not contain all the data required for its verification, and it
 is anticipated that some of the data not stored in the token may
 become unavailable during the interval between generation of the
 evidence token and verification unless it is stored in the token.
 The Form_Complete_PIDU operation gathers the missing information and
 includes it in the token so that verification can be guaranteed to be
 possible at any future time.

H.3. CORBA Security Interfaces Defined by the OMG

 Non-repudiation interfaces have been defined in "CORBA Security", a
 document produced by the OMG (Object Management Group).  These
 interfaces are described in IDL (Interface Definition Language) and
 are optional.
 The handling of "tokens" supporting non-repudiation is done through
 the following interfaces:
  1. set_NR_features specifies the features to apply to future

evidence generation and verification operations;

  1. get_NR_features returns the features that will be applied to

future evidence generation and verification operations;

  1. generate_token generates a non-repudiation token using the

current non-repudiation features;

  1. verify_evidence verifies the evidence token using the current

non-repudiation features;

  1. get_tokens_details returns information about an input

non-repudiation token. The information returned depends upon

      the type of token;
  1. form_complete_evidence is used when the evidence token itself

does not contain all the data required for its verification, and

      it is anticipated that some of the data not stored in the token
      may become unavailable during the interval between generation of

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      the evidence token and verification unless it is stored in the
      token.  The form_complete_evidence operation gathers the missing
      information and includes it in the token so that verification
      can be guaranteed to be possible at any future time.
    NOTE: The similarity between the two sets of APIs is noticeable.

Annex I (Informative): Cryptographic Algorithms

 RFC 3370 [10] describes the conventions for using several
 cryptographic algorithms with the Crytographic Message Syntax (CMS).
 Only the hashing and signing algorithms are appropriate for use with
 the present document.
 Since the publication of RFC 3370 [10], MD5 has been broken.  This
 algorithm is no longer considered appropriate and has been deleted
 from the list of algorithms.

I.1. Digest Algorithms

I.1.1. SHA-1

 The SHA-1 digest algorithm is defined in FIPS Pub 180-1.  The
 algorithm identifier for SHA-1 is:

sha-1 OBJECT IDENTIFIER ::= { iso(1) identified-organization(3) oiw(14) secsig(3) algorithm(2) 26 }

 The AlgorithmIdentifier parameters field is optional.  If present,
 the parameters field shall contain an ASN.1 NULL.  Implementations
 should accept SHA-1 AlgorithmIdentifiers with absent parameters as
 well as NULL parameters.  Implementations should generate SHA-1
 AlgorithmIdentifiers with NULL parameters.

I.1.2. General

 The following is a selection of work that has been done in the area
 of digest algorithms or, as they are often called, hash functions:
  1. ISO/IEC 10118-1 (1994) [ISO10118-1]: "Information technology -

Security techniques - Hash-functions - Part 1: General". ISO/IEC

      10118-1 contains definitions and describes basic concepts.
  1. ISO/IEC 10118-2 (1994) [ISO10118-2]: "Information technology -

Security techniques - Hash-functions - Part 2: Hash-functions

      using an n-bit block cipher algorithm".  ISO/IEC 10118-2
      specifies two ways to construct a hash-function from a block
      cipher.

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  1. ISO/IEC 10118-3 (1997) [ISO10118-3]: "Information technology -

Security techniques - Hash-functions - Part 3: Dedicated

      hash-functions".  ISO/IEC 10118-3 specifies the following
      dedicated hash-functions:
  1. SHA-1 (FIPS 180-1);
  2. RIPEMD-128;
  3. RIPEMD-160.
  1. ISO/IEC 10118-4 (1998) [ISO10118-4]: "Information technology -

Security techniques - Hash-functions - Part 4: Hash-functions

      using modular arithmetic".
  1. RFC 1320 (PS 1992): "The MD4 Message-Digest Algorithm". RFC

1320 specifies the hash-function MD4. Today, MD4 is considered

      outdated.
  1. RFC 1321 (I 1992): "The MD5 Message-Digest Algorithm". RFC 1321

(informational) specifies the hash-function MD5. Today, MD5 is

      not recommended for new implementations.
  1. FIPS Publication 180-1 (1995): "Secure Hash Standard". FIPS

180-1 specifies the Secure Hash Algorithm (SHA), dedicated hash-

      function developed for use with the DSA.  The original SHA,
      published in 1993, was slightly revised in 1995 and renamed
      SHA-1.
  1. ANSI X9.30-2 (1997) [X9.30-2]: "Public Key Cryptography for the

Financial Services Industry - Part 2: The Secure Hash Algorithm

      (SHA-1)".  X9.30-2 specifies the ANSI-Version of SHA-1.
  1. ANSI X9.31-2 (1996) [X9.31-2]: "Public Key Cryptography Using

Reversible Algorithms for the Financial Services Industry - Part

      2: Hash Algorithms".  X9.31-2 specifies hash algorithms.

I.2. Digital Signature Algorithms

I.2.1. DSA

 The DSA signature algorithm is defined in FIPS Pub 186.  DSA is
 always used with the SHA-1 message digest algorithm.  The algorithm
 identifier for DSA is:

id-dsa-with-sha1 OBJECT IDENTIFIER ::= { iso(1) member-body(2) us(840) x9-57 (10040) x9cm(4) 3 }

 The AlgorithmIdentifier parameters field shall not be present.

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I.2.2. RSA

 The RSA signature algorithm is defined in RFC 3447 [RFC3447].  RFC
 3370 [10] specifies the use of the RSA signature algorithm with the
 SHA-1 algorithm.  The algorithm identifier for RSA with SHA-1 is:
 Sha1WithRSAEncryption OBJECT IDENTIFIER ::= { iso(1) member-body(2)
 us(840) rsadsi(113549) pkcs(1) pkcs-1(1) 5 }
    NOTE: RFC 3370 [10] recommends that MD5 not be used for new
    implementations.

I.2.3. General

    The following is a selection of work that has been done in the
    area of digital signature mechanisms:
  1. FIPS Publication 186 (1994): "Digital Signature Standard".

NIST's Digital Signature Algorithm (DSA) is a variant of

      ElGamal's Discrete Logarithm-based digital signature mechanism.
      The DSA requires a 160-bit hash-function and mandates SHA-1.
  1. IEEE P1363 (2000) [P1363]: "Standard Specifications for Public-

Key Cryptography". IEEE P1363 contains mechanisms for digital

      signatures, key establishment, and encipherment based on three
      families of public key schemes:
  1. "Conventional" Discrete Logarithm (DL)-based techniques, i.e.,

Diffie-Hellman (DH) key agreement, Menezes-Qu-Vanstone (MQV) key

      agreement, the Digital Signature Algorithm (DSA), and
      Nyberg-Rueppel (NR) digital signatures;
  1. Elliptic Curve (EC)-based variants of the DL-mechanisms

specified above, i.e., EC-DH, EC-MQV, EC-DSA, and EC-NR. For

      elliptic curves, implementation options include mod p and
      characteristic 2 with polynomial or normal basis representation;
  1. Integer Factoring (IF)-based techniques, including RSA

encryption, RSA digital signatures, and RSA-based key transport.

  1. ISO/IEC 9796-2 (1997) [ISO9796-2]: "Information technology -

Security techniques - Digital signature schemes giving message

      recovery - Part 2: Mechanisms using a hash-function".  ISO/IEC
      9796-2 specifies digital signature mechanisms with partial
      message recovery that are also based on the RSA technique but
      make use of a hash-function.

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  1. ISO/IEC 9796-4 (1998) [ISO9796-4]: "Digital signature schemes

giving message recovery - Part 4: Discrete logarithm based

      mechanisms".  ISO/IEC 9796-4 specifies digital signature
      mechanisms with partial message recovery that are based on
      Discrete Logarithm techniques.  The document includes the
      Nyberg-Rueppel scheme.
  1. ISO/IEC 14888-1 [ISO14888-1]: "Digital signatures with appendix
    1. Part 1: General". ISO/IEC 14888-1 contains definitions and

describes the basic concepts of digital signatures with

      appendix.
  1. ISO/IEC 14888-2 [ISO14888-2]: "Digital signatures with appendix
    1. Part 2: Identity-based mechanisms". ISO/IEC 14888-2 specifies

digital signature schemes with appendix that make use of

      identity-based keying material.  The document includes the
      zero-knowledge techniques of Fiat-Shamir and Guillou-Quisquater.
  1. ISO/IEC 14888-3 [ISO14888-3]: "Digital signatures with appendix
    1. Part 3: Certificate-based mechanisms". ISO/IEC 14888-3

specifies digital signature schemes with appendix that make use

      of certificate-based keying material.  The document includes
      five schemes:
  1. DSA;
  2. EC-DSA, an elliptic curve-based analog of NIST's Digital

Signature Algorithm;

  1. Pointcheval-Vaudeney signatures;
  2. RSA signatures;
  3. ESIGN.
  1. ISO/IEC 15946-2 (2002) [ISO15946-2]: "Cryptographic techniques

based on elliptic curves - Part 2: Digital signatures",

      specifies digital signature schemes with appendix using elliptic
      curves.
  1. The document includes two schemes:
  1. EC-DSA, an elliptic curve-based analog of NIST's Digital

Signature Algorithm;

  1. EC-AMV, an elliptic curve-based analog of the Agnew-Muller-

Vanstone signature algorithm.

Pinkas, et al. Informational [Page 136] RFC 5126 CMS Advanced Electronic Signatures February 2008

  1. ANSI X9.31-1 (1997) [X9.31-1]: "Public Key Cryptography Using

Reversible Algorithms for the Financial Services Industry - Part

      1: The RSA Signature Algorithm".  ANSI X9.31-1 specifies a
      digital signature mechanism with appendix using the RSA public
      key technique.
  1. ANSI X9.30-1 (1997) [X9.30-1]: "Public Key Cryptography Using

Irreversible Algorithms for the Financial Services Industry -

      Part 1: The Digital Signature Algorithm (DSA)".  ANSI X9.30-1
      specifies the DSA, NIST's Digital Signature Algorithm.
  1. ANSI X9.62 (1998) [X9.62]: "Public Key Cryptography for the

Financial Services Industry - The Elliptic Curve Digital

      Signature Algorithm (ECDSA)".  ANSI X9.62 specifies the Elliptic
      Curve Digital Signature Algorithm, an analog of NIST's Digital
      Signature Algorithm (DSA) using elliptic curves.  The appendices
      provide tutorial information on the underlying mathematics for
      elliptic curve cryptography and give many examples.

Annex J (Informative): Guidance on Naming

J.1. Allocation of Names

 The subject name shall be allocated through a registration scheme
 administered through a Registration Authority (RA) to ensure
 uniqueness.  This RA may be an independent body or a function carried
 out by the Certification Authority.
 In addition to ensuring uniqueness, the RA shall verify that the name
 allocated properly identifies the applicant and that authentication
 checks are carried out to protect against masquerade.
 The name allocated by an RA is based on registration information
 provided by, or relating to, the applicant (e.g., his personal name,
 date of birth, residence address) and information allocated by the
 RA. Three variations commonly exist:
  1. the name is based entirely on registration information, which

uniquely identifies the applicant (e.g., "Pierre Durand (born

      on) July 6, 1956");
  1. the name is based on registration information, with the addition

of qualifiers added by the registration authority to ensure

      uniqueness (e.g., "Pierre Durand 12");
  1. the registration information is kept private by the registration

authority and the registration authority allocates a

      "pseudonym".

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J.2. Providing Access to Registration Information

 Under certain circumstances, it may be necessary for information used
 during registration, but not published in the certificate, to be made
 available to third parties (e.g., to an arbitrator to resolve a
 dispute or for law enforcement).  This registration information is
 likely to include personal and sensitive information.
 Thus, the RA needs to establish a policy for:
  1. whether the registration information should be disclosed;
  2. to whom such information should be disclosed;
  3. under what circumstances such information should be

disclosed.

 This policy may be different whether the RA is being used only within
 a company or for public use.  The policy will have to take into
 account national legislation and in particular any data protection
 and privacy legislation.
 Currently, the provision of access to registration is a local matter
 for the RA.  However, if open access is required, standard protocols,
 such as HTTP -- RFC 2068 (Internet Web Access Protocol), may be
 employed with the addition of security mechanisms necessary to meet
 the data protection requirements (e.g., Transport Layer Security --
 RFC 4346 [RFC4346]) with client authentication.

J.3. Naming Schemes

J.3.1. Naming Schemes for Individual Citizens

 In some cases, the subject name that is contained in a public key
 certificate may not be meaningful enough.  This may happen because of
 the existence of homonyms or because of the use of pseudonyms.  A
 distinction could be made if more attributes were present.  However,
 adding more attributes to a public key certificate placed in a public
 repository would be going against the privacy protection
 requirements.
 In any case, the Registration Authority will get information at the
 time of registration, but not all that information will be placed in
 the certificate.  In order to achieve a balance between these two
 opposite requirements, the hash values of some additional attributes
 can be placed in a public key certificate.  When the certificate
 owner provides these additional attributes, then they can be
 verified.  Using biometrics attributes may unambiguously identify a
 person.  Examples of biometrics attributes that can be used include:
 a picture or a manual signature from the certificate owner.

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    NOTE: Using hash values protects privacy only if the possible
    inputs are large enough.  For example, using the hash of a
    person's social security number is generally not sufficient since
    it can easily be reversed.
 A picture can be used if the verifier once met the person and later
 on wants to verify that the certificate that he or she got relates to
 the person whom was met.  In such a case, at the first exchange, the
 picture is sent, and the hash contained in the certificate may be
 used by the verifier to verify that it is the right person.  At the
 next exchange, the picture does not need to be sent again.
 A manual signature may be used if a signed document has been received
 beforehand.  In such a case, at the first exchange, the drawing of
 the manual signature is sent, and the hash contained in the
 certificate may be used by the verifier to verify that it is the
 right manual signature.  At the next exchange, the manual signature
 does not need to be sent again.

J.3.2. Naming Schemes for Employees of an Organization

 The name of an employee within an organization is likely to be some
 combination of the name of the organization and the identifier of the
 employee within that organization.
 An organization name is usually a registered name, i.e., business or
 trading name used in day-to-day business.  This name is registered by
 a Naming Authority, which guarantees that the organization's
 registered name is unambiguous and cannot be confused with another
 organization.
 In order to get more information about a given registered
 organization name, it is necessary to go back to a publicly available
 directory maintained by the Naming Authority.
 The identifier may be a name or a pseudonym (e.g., a nickname or an
 employee number).  When it is a name, it is supposed to be
 descriptive enough to unambiguously identify the person.  When it is
 a pseudonym, the certificate does not disclose the identity of the
 person.  However, it ensures that the person has been correctly
 authenticated at the time of registration and therefore may be
 eligible to some advantages implicitly or explicitly obtained through
 the possession of the certificate.  In either case, however, this can
 be insufficient because of the existence of homonyms.
 Placing more attributes in the certificate may be one solution, for
 example, by giving the organization unit of the person or the name of
 a city where the office is located.  However, the more information is

Pinkas, et al. Informational [Page 139] RFC 5126 CMS Advanced Electronic Signatures February 2008

 placed in the certificate, the more problems arise if there is a
 change in the organization structure or the place of work.  So this
 may not be the best solution.  An alternative is to provide more
 attributes (like the organization unit and the place of work) through
 access to a directory maintained by the company.  It is likely that,
 at the time of registration, the Registration Authority got more
 information than what was placed in the certificate, if such
 additional information is placed in a repository accessible only to
 the organization.

Acknowledgments

 Special thanks to Russ Housley for reviewing the document.

Authors' Addresses

 Denis Pinkas
 Bull SAS
 Rue Jean-Jaures
 78340 Les Clayes sous Bois CEDEX
 FRANCE
 EMail: Denis.Pinkas@bull.net
 Nick Pope
 Thales eSecurity
 Meadow View House
 Long Crendon
 Aylesbury
 Buck
 HP18 9EQ
 United Kingdom
 EMail: nick.pope@thales-esecurity.com
 John Ross
 Security & Standards Consultancy Ltd
 The Waterhouse Business Centre
 2 Cromer Way
 Chelmsford
 Essex
 CM1 2QE
 United Kingdom
 EMail: ross@secstan.com

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