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RFC 5754
S/MIME WG Sean Turner, IECA
Internet Draft January 16, 2009
Intended Status: Standard Track
Updates: 3370 (once approved)
Expires: July 16, 2009
Using SHA2 Algorithms with Cryptographic Message Syntax
draft-ietf-smime-sha2-11.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...................................................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. IANA Considerations............................................9
6. References....................................................10
6.1. Normative References.....................................10
6.2. Informative 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
(RSASSA-PKCS1-v1_5) [RFC3447], and ECDSA [DSS].
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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
[RFCTBD1] 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 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).
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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
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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.
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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 }
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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
(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 }
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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 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
[RFCTBD2] 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 }
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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 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],
[RFCTBD2], 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.
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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-05.txt (work-in-progress).
[DSS] National Institute of Standards and Technology (NIST),
FIPS Publication 186-3: Digital Signature Standard,
(draft) November 2008.
[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] 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.
[RFCTBD1] 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 TBD1 with the RFC # for draft-
ietf-smime-3851bis-08.txt. *//
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[RFCTBD2] Turner, S., and D. Brown, "Use of Elliptic Curve
Cryptography (ECC) Algorithms in Cryptographic Message
Syntax (CMS)", draft-ietf-smime-3278bis-05, work-in-
progress.
//* RFC EDITOR: Note replace the above TBD2 with the RFC # for draft-
ietf-smime-3278bis-05.txt. *//
[SHS] National Institute of Standards and Technology (NIST),
FIPS Publication 180-3: Secure Hash Standard, October
2008.
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.
Author's Addresses
Sean Turner
IECA, Inc.
3057 Nutley Street, Suite 106
Fairfax, VA 22031
USA
EMail: turners@ieca.com
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