S/MIME WG                                             Sean Turner, IECA
Internet Draft                                       September 24, 2008
Intended Status: Standard Track
Expires: March 24, 2009


          Using SHA2 Algorithms with Cryptographic Message Syntax
                       draft-ietf-smime-sha2-08.txt


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Copyright Notice

   Copyright (C) The IETF Trust (2008).

Abstract

   This document describes the conventions for using the Secure Hash
   Algorithm (SHA) message digest algorithms (SHA-224, SHA-256, SHA-384,
   SHA-512) with the Cryptographic Message Syntax (CMS). It also
   describes the conventions for using these algorithms with CMS and the
   Digital Signature Algorithm (DSA), Rivest Shamir Adleman (RSA), and
   Elliptic Curve DSA (ECDSA) signature algorithms.




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Conventions used in this document

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in [RFC2119].

Table of Contents

   1. Introduction...................................................2
   2. Message Digest Algorithms......................................3
      2.1. SHA-224...................................................4
      2.2. SHA-256...................................................4
      2.3. SHA-384...................................................4
      2.4. SHA-512...................................................4
   3. Signature Algorithms...........................................5
      3.1. DSA.......................................................5
      3.2. RSA.......................................................6
      3.3. ECDSA.....................................................6
   4. Security Considerations........................................7
   5. IANA Considerations............................................7
   6. References.....................................................7
      6.1. Normative References......................................7
      6.2. Informative References....................................8

. Introduction

   This document specifies the algorithm identifiers and specifies
   parameters for the message digest algorithms SHA-224, SHA-256, SHA-
   384, and SHA-512 for use with the Cryptographic Message Syntax (CMS)
   [RFC3852].  The message digest algorithms are defined in [SHS] and
   reference code is provided in [RFC4634].

   This document also specifies the algorithm identifiers and parameters
   for use of SHA-224, SHA-256, SHA-384, and SHA-512 with DSA [DSS], RSA
   [RFC2313], and ECDSA [X9.62].

   This document does not define new identifiers; they are taken from
   [RFC3874], [RFC4055], [ECCADD], and [RFC3278].  Additionally, the
   parameters follow the conventions specified therein.  Therefore,
   there is no Abstract Syntax Notation One (ASN.1) module included in
   this document.

   Note that [RFC4231] specifies the conventions for the message
   authentication code (MAC) algorithms: HMAC with SHA-224, HMAC with
   SHA-256, HMAC with SHA-384, and HMAC with SHA-512.




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   In CMS, the various algorithm identifiers use the AlgorithmIdentifier
   syntax, which is included here for convenience:

     AlgorithmIdentifier  ::=  SEQUENCE  {
       algorithm   OBJECT IDENTIFIER,
       parameters  ANY DEFINED BY algorithm OPTIONAL  }

. Message Digest Algorithms

   Digest algorithm identifiers are located in the SignedData
   digestAlgorithms field, the SignerInfo digestAlgorithm field, the
   DigestedData digestAlgorithm field, and the AuthenticatedData
   digestAlgorithm field.

   Digest values are located in the DigestedData digest field and the
   Message Digest authenticated attribute.  In addition, digest values
   are input to signature algorithms.

   The digest algorithm identifiers use the AlgorithmIdentifier syntax
   elaborated upon in Section 1.

   The algorithm field is discussed in Sections 2.1-2.4 for each message
   digest algorithm.

   There are two possible encodings for the SHA AlgorithmIdentifier
   parameters field.  The two alternatives arise from the fact that when
   the 1988 syntax for AlgorithmIdentifier was translated into the 1997
   syntax, the OPTIONAL associated with the AlgorithmIdentifier
   parameters got lost.  Later the OPTIONAL was recovered via a defect
   report, but by then many people thought that algorithm parameters
   were mandatory.  Because of this history some implementations encode
   parameters as a NULL element and others omit them entirely.  The
   correct encoding is to omit the parameters field; however,
   implementations MUST also handle a SHA AlgorithmIdentifier parameters
   field which contains a NULL.

   The AlgorithmIdentifier parameters field is OPTIONAL.  If present,
   the parameters field MUST contain a NULL.  Implementations MUST
   accept SHA2 AlgorithmIdentifiers with absent parameters.
   Implementations MUST accept SHA2 AlgorithmIdentifiers with NULL
   parameters.  Implementations SHOULD generate SHA2
   AlgorithmIdentifiers with absent parameters.







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2.1. SHA-224

   The SHA-224 message digest algorithm is defined in [SHS].  The
   algorithm identifier for SHA-224 is:

     id-sha224 OBJECT IDENTIFIER ::= {
        joint-iso-itu-t(2) country(16) us(840) organization(1) gov(101)
        csor(3) nistalgorithm(4) hashalgs(2) 4 }

   The parameters are as specified in Section 2.

2.2. SHA-256

   The SHA-256 message digest algorithm is defined in [SHS].  The
   algorithm identifier for SHA-256 is:

    id-sha256 OBJECT IDENTIFIER ::= {
        joint-iso-itu-t(2) country(16) us(840) organization(1) gov(101)
        csor(3) nistalgorithm(4) hashalgs(2) 1 }

   The parameters are as specified in Section 2.

2.3. SHA-384

   The SHA-384 message digest algorithm is defined in [SHS].  The
   algorithm identifier for SHA-384 is:

     id-sha384 OBJECT IDENTIFIER ::= {
       joint-iso-itu-t(2) country(16) us(840) organization(1) gov(101)
       csor(3) nistalgorithm(4) hashalgs(2) 2 }

   The parameters are as specified in Section 2.

2.4. SHA-512

   The SHA-512 message digest algorithm is defined in [SHS].  The
   algorithm identifier for SHA-512 is:

     id-sha512 OBJECT IDENTIFIER ::= {
       joint-iso-itu-t(2) country(16) us(840) organization(1) gov(101)
       csor(3) nistalgorithm(4) hashalgs(2) 3 }

   The parameters are as specified in Section 2.






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. Signature Algorithms

   This section specifies the conventions employed by CMS
   implementations that support DSA, RSA, and ECDSA with SHA2
   algorithms.

   Signature algorithm identifiers are located in the SignerInfo
   signatureAlgorithm field of SignedData.  Also, signature algorithm
   identifiers are located in the SignerInfo signatureAlgorithm field of
   countersignature attributes.

   Signature values are located in the SignerInfo signature field of
   SignedData.  Also, signature values are located in the SignerInfo
   signature field of countersignature attributes.

3.1. DSA

   [RFC3370] section 3.1 specifies the conventions for DSA with SHA-1
   public key algorithm identifiers, parameters, public keys, and
   signature values. DSA with SHA2 algorithms uses the same conventions
   for these public key algorithm identifiers, parameters, public keys,
   and signature values.  DSA MAY be used with SHA-224 and SHA-256.

   DSA has not been specified with SHA-384 and SHA-512.  SHA-384 and
   SHA-512 are not supported because the maximum bit length of p
   (specified as L) is 3072 for DSA.  For consistent cryptographic
   strength, SHA-384 would be used with DSA where L is 7680, and SHA-512
   would be used with DSA where L is 15360.

   The algorithm identifier for DSA with SHA-224 signature values is:

     id-dsa-with-sha224 OBJECT IDENTIFIER ::=  { joint-iso-ccitt(2)
       country(16) us(840) organization(1) gov(101) csor(3)
       algorithms(4) id-dsa-with-sha2(3) 1 }

   The algorithm identifier for DSA with SHA-256 signature values is:

     id-dsa-with-sha256 OBJECT IDENTIFIER ::=  { joint-iso-ccitt(2)
       country(16) us(840) organization(1) gov(101) csor(3)
       algorithms(4) id-dsa-with-sha2(3) 2 }

   When either of these algorithm identifiers is used, the
   AlgorithmIdentifier parameters field MUST be absent.






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3.2. RSA

   [RFC3370] section 3.2 specifies the conventions for RSA with SHA-1
   (PKCS #1 v1.5) public key algorithm identifiers, parameters, public
   keys, and signature values. RSA with SHA2 algorithms uses the same
   conventions for these public key algorithm identifiers, parameters,
   public keys, and signature values.  RSA (PKCS #1 v1.5) MAY be used
   with SHA-224, SHA-256, SHA-384, or SHA-512.

   The object identifier for RSA with SHA-224 signature values is:

     sha224WithRSAEncryption OBJECT IDENTIFIER ::= { iso(1)
       member-body(2) us(840) rsadsi(113549) pkcs(1) pkcs-1(1) 14 }

   The object identifier for RSA with SHA-256 signature values is:

     sha256WithRSAEncryption  OBJECT IDENTIFIER  ::=  { iso(1)
       member-body(2) us(840) rsadsi(113549) pkcs(1) pkcs-1(1) 11 }

   The object identifier for RSA with SHA-384 signature values is:

     sha384WithRSAEncryption  OBJECT IDENTIFIER  ::=  { iso(1)
       member-body(2) us(840) rsadsi(113549) pkcs(1) pkcs-1(1) 12 }

   The object identifier for RSA with SHA-512 signature values is:

     sha512WithRSAEncryption  OBJECT IDENTIFIER  ::=  { iso(1)
       member-body(2) us(840) rsadsi(113549) pkcs(1) pkcs-1(1) 13 }

   When any of these four object identifiers appears within an
   AlgorithmIdentifier, the parameters MUST be NULL.  Implementations
   MUST accept the parameters being absent as well as present.

3.3. ECDSA

   [RFC3278] section 2.1 specifies the conventions for ECDSA with SHA-1
   public key algorithm identifiers, parameters, public keys, and
   signature values. ECDSA with SHA2 algorithms uses the same
   conventions for these public key algorithm identifiers, parameters,
   public keys, and signature values, except that the digestAlgorithm
   MUST include the corresponding message digest algorithm identifier,
   and not the sha-1 object identifier.  ECDSA MAY be used with SHA-224,
   SHA-256, SHA-384, or SHA-512.






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   The algorithm identifier for ECDSA with SHA-224 signature values is:

     ecdsa-with-SHA224 OBJECT IDENTIFIER ::= { iso(1) member-body(2)
       us(840) ansi-X9-62(10045) signatures(4) ecdsa-with-SHA2(3) 1 }

   The algorithm identifier for ECDSA with SHA-256 signature values is:

     ecdsa-with-SHA256 OBJECT IDENTIFIER ::= { iso(1) member-body(2)
       us(840)ansi-X9-62(10045) signatures(4) ecdsa-with-SHA2(3) 2 }

   The algorithm identifier for ECDSA with SHA-384 signature values is:

     ecdsa-with-SHA384 OBJECT IDENTIFIER ::= { iso(1) member-body(2)
       us(840) ansi-X9-62(10045) signatures(4) ecdsa-with-SHA2(3) 3 }

   The algorithm identifier for ECDSA with SHA-512 signature values is:

     ecdsa-with-SHA512 OBJECT IDENTIFIER ::= { iso(1) member-body(2)
       us(840) ansi-X9-62(10045) signatures(4) ecdsa-with-SHA2(3) 4 }

   When any of these four object identifiers appears within an
   AlgorithmIdentifier, the parameters MUST omit the parameters field.
   That is, the AlgorithmIdentifier SHALL be a SEQUENCE of one
   component: the OID ecdsa-with-SHA224, ecdsa-with-SHA256,
   ecdsa-with-SHA384 or ecdsa-with-SHA512.

. Security Considerations

   The security considerations in [RFC3278], [RFC3370], [RFC3874],
   [RFC4055], and [ECCADD] apply. No new security considerations are
   introduced as a result of this specification.

. IANA Considerations

   None: All identifiers are already registered.  Please remove this
   section prior to publication as an RFC.

. References

6.1. Normative References

   [ECCADD]    Dang, S., Santesson, S., Moriarty, K., and Brown,
               "Internet X.509 Public Key Infrastructure: Additional
               Algorithms and Identifiers for DSA and ECDSA", work-in-
               progress.




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   [DSS]       National Institute of Standards and Technology (NIST),
               FIPS Publication 186-3: Digital Signature Standard, March
               2006.

   [RFC2119]   Bradner, S., "Key words for use in RFCs to Indicate
               Requirement Levels", BCP 14, RFC 2119. March 1997.

   [RFC2313]   Kaliski, B., "PKCS #1: RSA Encryption Version 1.5", RFC
               2313, March 1998.

   [RFC3278]   Blake-Wilson, S., Brown, D., and P. Lambert, "Use of
               Elliptic Curve Cryptography (ECC) Algorithms in
               Cryptographic Message Syntax (CMS)", RFC 3278, April
               2002.

   [RFC3370]   Housley, R., "Cryptographic Message Syntax (CMS)
               Algorithms", RFC 3370, August 2002.

   [RFC3852]   Housley, R., "The Cryptographic Message Syntax (CMS)",
               RFC 3852. July 2004.

   [RFC3874]   Housley, R., "A 224-bit One Way Hash Function: SHA-224",
               RFC 3874. September 2004.

   [RFC4055]   Schaad, J., Kaliski, B., and R. Housley, "Additional
               Algorithms and Identifiers for RSA Cryptography for use
               in the Internet Public Key Infrastructure Certificate and
               Certificate Revocation List (CRL) Profile", RFC 4055.
               June 2005.

   [SHS]       National Institute of Standards and Technology (NIST),
               FIPS Publication 180-3: Secure Hash Standard, June 2003.

   [X9.62]     X9.62-2005, "Public Key Cryptography for the Financial
               Services Industry: The Elliptic Curve Digital Signature
               Standard (ECDSA)", November, 2005.

6.2. Informative References

   [RFC4231]   Nystrom, A. "Identifiers and Test Vectors for HMAC-SHA-
               224, HMAC-SHA-256, HMAC-SHA-384, and HMAC-SHA-512",
               RFC4231. December 2005.

   [RFC4634]   Eastlake, D., and T. Hansen, "US Secure Hash Algorithms
               (SHA and HMAC-SHA)", RFC 4634, July 2006.




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Author's Addresses

   Sean Turner

   IECA, Inc.
   3057 Nutley Street, Suite 106
   Fairfax, VA 22031
   USA

   EMail: turners@ieca.com







































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