Using SHA2 Algorithms with Cryptographic Message Syntax

Internet Engineering Task Force (IETF)                         S. Turner
Request for Comments: 5754                                          IECA
Updates: 3370                                               January 2010
Category: Standards Track
ISSN: 2070-1721


        Using SHA2 Algorithms with Cryptographic Message Syntax

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 the 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.

Status of This Memo

   This is an Internet Standards Track document.

   This document is a product of the Internet Engineering Task Force
   (IETF).  It represents the consensus of the IETF community.  It has
   received public review and has been approved for publication by the
   Internet Engineering Steering Group (IESG).  Further information on
   Internet Standards is available in Section 2 of RFC 5741.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at
   http://www.rfc-editor.org/info/rfc5754.

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Table of Contents

   1. Introduction ....................................................2
      1.1. Conventions Used in This Document ..........................3
   2. Message Digest Algorithms .......................................3
      2.1. SHA-224 ....................................................4
      2.2. SHA-256 ....................................................5
      2.3. SHA-384 ....................................................5
      2.4. SHA-512 ....................................................5
   3. Signature Algorithms ............................................6
      3.1. DSA ........................................................6
      3.2. RSA ........................................................7
      3.3. ECDSA ......................................................8
   4. Security Considerations .........................................9
   5. References ......................................................9
      5.1. Normative References .......................................9
      5.2. Informative References ....................................10

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) [RFC5652].  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
   (RSASSA-PKCS1-v1_5) [RFC3447], and ECDSA [DSS].

   This document does not define new identifiers; they are taken from
   [RFC3874], [RFC4055], and [RFC5758].  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: Hashed MAC (HMAC) with SHA-224,
   HMAC with SHA-256, HMAC with SHA-384, and HMAC with SHA-512.

   In the 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
   [RFC5751] 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 }

1.1.  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].

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 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 the beginning of 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 the beginning of 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 the beginning of 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 the beginning of 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 [RFC5758].

   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 encodings 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
   (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
   (RSASSA-PKCS1-v1_5) [RFC3447] MAY be used with SHA-224, SHA-256,
   SHA-384, or 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 encodings
   for these SMIMECapability values are:

      sha224WithRSAEncryption: 30 0d 06 09 2a 86 48 86 f7 0d 01 01 0e
                               05 00

      sha256WithRSAEncryption: 30 0d 06 09 2a 86 48 86 f7 0d 01 01 0b
                               05 00

      sha384WithRSAEncryption: 30 0d 06 09 2a 86 48 86 f7 0d 01 01 Oc
                               05 00

      sha512WithRSAEncryption: 30 0d 06 09 2a 86 48 86 f7 0d 01 01 0d
                               05 00

3.3.  ECDSA

   [RFC5753], Section 2.1, specifies the conventions for ECDSA with
   SHA-* (where * is 1, 224, 256, 384, or 512) public key algorithm
   identifiers, parameters, public keys, and signature values.  The
   object identifiers, which are included below for convenience, are
   taken from [RFC5758].

   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 field 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 encodings 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],
   [RFC5753], and [RFC5758] apply.  No new security considerations are
   introduced as a result of this specification.

5.  References

5.1.  Normative References

   [DSS]       National Institute of Standards and Technology (NIST),
               FIPS Publication 186-3: Digital Signature Standard, June
               2009.

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

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

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

   [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 X.509 Public Key Infrastructure
               Certificate and Certificate Revocation List (CRL)
               Profile", RFC 4055, June 2005.

   [RFC5652]   Housley, R., "Cryptographic Message Syntax (CMS)", RFC
               5652, September 2009.

   [RFC5751]   Ramsdell, B. and S. Turner, "Secure/Multipurpose Internet
               Mail Extensions (S/MIME) Version 3.2 Message
               Specification", RFC 5751, January 2010.

   [RFC5753]   Turner, S. and D. Brown, "Use of Elliptic Curve
               Cryptography (ECC) Algorithms in Cryptographic Message
               Syntax (CMS)", RFC 5753, January 2010.

   [RFC5758]   Dang, Q., Santesson, S., Moriarty, K., Brown, D., and T.
               Polk, "Internet X.509 Public Key Infrastructure:
               Additional Algorithms and Identifiers for DSA and ECDSA",
               RFC 5758, January 2010.

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

5.2.  Informative References

   [RFC4231]   Nystrom, M., "Identifiers and Test Vectors for HMAC-
               SHA-224, HMAC-SHA-256, HMAC-SHA-384, and HMAC-SHA-512",
               RFC 4231, December 2005.

   [RFC4634]   Eastlake 3rd, D. and T. Hansen, "US Secure Hash
               Algorithms (SHA and HMAC-SHA)", RFC 4634, July 2006.

Author's Address

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

   EMail: turners@ieca.com