S/MIME WG                                             Sean Turner, IECA

Intended Status: Standard Track
Updates: 3370 (once approved)
Expires: April 6, June 20, 2009

          Using SHA2 Algorithms with Cryptographic Message Syntax
                       draft-ietf-smime-sha2-09.txt
                       draft-ietf-smime-sha2-10.txt

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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.  Further, it
   provides SMIMECapabilities attribute values for each algorithm.

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...................................................3 SHA-224...................................................4
      2.2. SHA-256...................................................4 SHA-256...................................................5
      2.3. SHA-384...................................................4 SHA-384...................................................5
      2.4. SHA-512...................................................4 SHA-512...................................................5
   3. Signature Algorithms...........................................4 Algorithms...........................................6
      3.1. DSA.......................................................5 DSA.......................................................6
      3.2. RSA.......................................................5 RSA.......................................................7
      3.3. ECDSA.....................................................6 ECDSA.....................................................8
   4. Security Considerations........................................7 Considerations........................................9
   5. IANA Considerations............................................7 Considerations............................................9
   6. References.....................................................7 References....................................................10
      6.1. Normative References......................................7 References.....................................10
      6.2. Informative References....................................8 References...................................11

1. 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],
   (RSASSA-PKCS1-v1_5) [RFC3447], and ECDSA [DSS].

   This document does not define new identifiers; they are taken from
   [RFC3874], [RFC4055], and [ECCADD].  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.

   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  }

   This document also specifies the SMIMECapabilities attribute values
   [RFCTBD] for each algorithm.  The values provided are for the
   SMIMECapability field, which is included here for convenience:

     SMIMECapability ::= SEQUENCE {
       capabilityID  OBJECT IDENTIFIER,
       parameters    ANY DEFINED BY capabilityID OPTIONAL }

2. 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.  The object identifiers are taken from
   [RFC4055].

   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 and SMIMECapabilities attribute are discussed in
   Sections 2.1-2.4 for each message digest algorithm.  Section 3
   provides some signatures that use SHA2 algorithms.  Consult the
   signature algorithm definitions for the procedures to compute the
   digest values (i.e., DigestInfo).

   The AlgorithmIdentifier parameters field is OPTIONAL.
   Implementations MUST accept SHA2 AlgorithmIdentifiers with absent
   parameters.  Implementations MUST accept SHA2 AlgorithmIdentifiers
   with NULL parameters.  Implementations MUST generate SHA2
   AlgorithmIdentifiers with absent parameters.

   NOTE: There are two possible encodings for the AlgorithmIdentifier
   parameters field associated with these object identifiers.  The two
   alternatives arise from the loss of the OPTIONAL associated with the
   algorithm identifier parameters when the 1988 syntax for
   AlgorithmIdentifier was translated into the 1997 syntax.  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
   while others omit them entirely.  The correct encoding is to omit the
   parameters field; however, when some uses of these algorithms were
   defined, it was done using the NULL parameters rather than absent
   parameters.  For example, PKCS#1 [RFC3447] requires that the padding
   used for RSA signatures (EMSA-PKCS1-v1_5) MUST use SHA2
   AlgorithmIdentifiers with NULL parameters (to clarify, the
   requirement "MUST generate SHA2 AlgorithmIdentifiers with absent
   parameters" in the previous paragraph does not apply to this
   padding).

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.

   The SMIMECapabilities attribute value indicates support for SHA-224
   in a SEQUENCE with the capabilityID field containing the object
   identifier id-sha224 with absent parameters.  The DER encoding for
   this SMIMECapability is:

      id-sha224: 30 0b 06 09 60 86 48 01 65 03 04 02 04

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.

   The SMIMECapabilities attribute value indicates support for SHA-256
   in a SEQUENCE with the capabilityID field containing the object
   identifier id-sha256 with absent parameters.  The DER encoding for
   this SMIMECapability value is:

      id-sha256: 30 0b 06 09 60 86 48 01 65 03 04 02 01

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.

   The SMIMECapabilities attribute value indicates support for SHA-384
   in a SEQUENCE with the capabilityID field containing the object
   identifier id-sha384 with absent parameters.  The DER encoding for
   this SMIMECapability value is:

      id-sha384: 30 0b 06 09 60 86 48 01 65 03 04 02 02

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.

   The SMIMECapabilities attribute value indicates support for SHA-384
   in a SEQUENCE with the capabilityID field containing the object
   identifier id-sha384 with absent parameters.  The DER encoding for
   this SMIMECapability value is:

      id-sha512: 30 0b 06 09 60 86 48 01 65 03 04 02 03

3. 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.  The
   object identifiers are taken from [ECCADD].

   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.

   The SMIMECapabilities attribute value indicates support for one of
   the DSA signature algorithms in a SEQUENCE with the capabilityID
   field containing the object identifier id-dsa-with-sha* (where * is
   224 or 256) with absent parameters.  The DER encoding for these
   SMIMECapability values are:

      id-dsa-with-sha224: 30 0b 06 09 60 86 48 01 65 03 04 03 01

      id-dsa-with-sha256: 30 0b 06 09 60 86 48 01 65 03 04 03 02

3.2. RSA

   [RFC3370] section 3.2 specifies the conventions for RSA with SHA-1
   (PKCS #1 v1.5)
   (RSASSA-PKCS1-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) (RSASSA-PKCS1-
   v1_5) [RFC3447] MAY be used with SHA-224, SHA-256, SHA-384, or SHA-512. SHA-
   512.  The object identifiers are taken from [RFC4055].

   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.

   The SMIMECapabilities attribute value indicates support for one of
   the DSA signature algorithms in a SEQUENCE with the capabilityID
   field containing the object identifier sha*WithRSAEncryption (where *
   is 224, 256, 384, or 512) with NULL parameters.  The DER encoding for
   these SMIMECapability values are:

      sha224WithRSAEncryption: 30 0d 06 08 2a 86 48 86 f7 0d 01 01 14
                               05 00

      sha256WithRSAEncryption: 30 0d 06 08 2a 86 48 86 f7 0d 01 01 11
                               05 00

      sha384WithRSAEncryption: 30 0d 06 08 2a 86 48 86 f7 0d 01 01 12
                               05 00

      sha512WithRSAEncryption: 30 0d 06 08 2a 86 48 86 f7 0d 01 01 13
                               05 00

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.  The object identifiers are taken from
   [ECCADD].

   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 filed MUST be absent.  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.

   The SMIMECapabilities attribute value indicates support for one of
   the ECDSA signature algorithms in a SEQUENCE with the capabilityID
   field containing the object identifier ecdsa-with-SHA1* (where * is
   224, 256, 384, or 512) with absent parameters.  The DER encoding for
   these SMIMECapability values are:

      ecdsa-with-SHA224: 30 0a 06 08 2a 86 48 ce 3d 04 03 01

      ecdsa-with-SHA256: 30 0a 06 08 2a 86 48 ce 3d 04 03 02

      ecdsa-with-SHA384: 30 0a 06 08 2a 86 48 ce 3d 04 03 03

      ecdsa-with-SHA512: 30 0a 06 08 2a 86 48 ce 3d 04 03 04

4. Security Considerations

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

5. IANA Considerations

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

6. 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",  draft-
               ietf-pkix-sha2-dsa-ecdsa-04.txt
               ietf-pkix-sha2-dsa-ecdsa-05.txt (work-in-progress).

   [DSS]       National Institute of Standards and Technology (NIST),
               FIPS Publication 186-3: Digital Signature Standard,
               (draft) March 2006. November 2008.

   [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.

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

   [RFC3447]   Kaliski, B. and J. Jonsson "Public-Key Cryptography
               Standards (PKCS) #1: RSA Cryptography Specifications
               Version 2.1", RFC 3447, February 2003.

   [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.

   [RFCTBD]    Ramsdell, B., and S. Turner, "S/MIME Version 3.2  Message
               Specification", draft-ietf-smime-3851bis-08.txt, work-in-
               progress.

   //* RFC EDITOR: Note replace the above TBD with the RFC # for draft-
   ietf-smime-3851bis-08.txt. *//

   [SHS]       National Institute of Standards and Technology (NIST),
               FIPS Publication 180-3: Secure Hash Standard, (draft)
               June 2003. October
               2008.

6.2. Informative References

   [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.

   [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.

Author's Addresses

   Sean Turner

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

   EMail: turners@ieca.com

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