S/MIME WG S. Turner
Internet Draft IECA, Inc.
Intended Status: Standard Track July 25, 2007
Expires: January 25, 2008
Using SHA2 Algorithms with Cryptographic Message Syntax
draft-ietf-smime-sha2-01.txt
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Copyright (C) The IETF Trust (2007).
Abstract
This document describes the conventions for using the message digest
algorithms SHA-224, as defined in [RFC3874], and SHA-256, SHA-384,
SHA-512, as defined in [SHA2], with the Cryptographic Message Syntax
(CMS) [RFC3852]. It also describes the conventions for using these
algorithms with CMS and the DSA, RSA, and 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
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 [RFC3874]
and [SHA2]. If an implementation chooses to support one of the
algorithms discussed in this document, then the implementation MUST
do so as described in this document.
This document also specifies the algorithm identifier and parameters
for use of SHA-224, SHA-256, SHA-384, and SHA-512 with DSA, RSA, and
ECDSA. If an implementation chooses to support one of the algorithms
discussed in this document, then the implementation MUST do so as
described in this document.
This document does not define new identifiers; they are taken from
[RFC3874], [RFC4055], [ECCADD], [RFC3278], and [RFC3370].
Additionally, the parameters follow the conventions specified
therein. Therefore, there is no ASN.1 module included in this
document.
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Note that [RFC4231] specifies the conventions for use of for the
message authentication code (MAC) algorithms: HMAC with SHA-224, HMAC
with SHA-256, HMAC with SHA-384, and HMAC with SHA-512.
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.
Digest values are located in the DigestedData digest field and the
Message Digest authenticated attribute. In addition, digest values
are input to signature algorithms.
In CMS, the digest algorithm identifiers use the AlgorithmIdentifier
syntax, which is included here for convenience:
AlgorithmIdentifier ::= SEQUENCE {
algorithm OBJECT IDENTIFIER,
parameters ANY DEFINED BY algorithm OPTIONAL }
The algorithm field is discussed in Sections 2.1-2.4 for each message
digest algorithm.
The following addresses the parameters field:
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 [RFC3874]. 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 [SHA2]. 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 [SHA2]. 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-256 message digest algorithm is defined in [SHA2]. 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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3. Signature Algorithms
This section specifies the conventions employed by CMS
implementations that support DSA [FIPS 186-3], ECDSA [X9.62], and RSA
[RFC2313] 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
</NOTE WELL
NIST has not finalized FIPS 186-3 and there is a chance that the
draft may be changed. This may result in differences between what is
documented here and what is in the FIPS.
/NOTE WELL>
[RFC3370] section 3.1 specifies the conventions for DSA with SHA1
public key algorithm identifiers, parameters, public keys, and
signature values. DSA with SHA2 algorithms use 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 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-224 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 are 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 use 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 SHA1
public key algorithm identifiers, parameters, public keys, and
signature values. ECDSA with SHA2 algorithms use 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 not 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 be NULL.
4. 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.
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", work-in-
progress.
[FIPS186-3] Federal Information Processing Standards Publication
(FIPS PUB) 180-3, Secure Hash Standard (SHS), July 2007.
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[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.
Housley, R., "Cryptographic Message Syntax (CMS) Multiple
Signer Clarification", RFC 4852, April 2007.
[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.
[SHA2] National Institute of Standards and Technology (NIST),
FIPS Publication 180-2: Secure Hash Standard, 1 August
2002.
[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.
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Author's Addresses
Sean Turner
IECA, Inc.
Email: turners@ieca.com
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