RFC 5754
Using SHA2 Algorithms with Cryptographic Message Syntax
RFC 5754: Using SHA2 Algorithms with Cryptographic Message Syntax 🎀
okay so this one's by S. Turner from IECA, dated January 2010, and it's a Standards Track doc, so it's the real deal and not just a suggestion 💅. It updates RFC 3370, and it doesn't list anything it obsoletes. The ISSN is 2070-1721 🦋. Also, the RFC number is 5754, so bookmark that one bestie 🔖
Abstract ✨
okay so this doc explains how to use the SHA-224, SHA-256, SHA-384, and SHA-512 message digest algorithms (the SHA2 family 🫶) with the Cryptographic Message Syntax (CMS). It also covers using those same algorithms with the DSA, RSA, and ECDSA signature algorithms, and it gives you the SMIMECapabilities attribute values for each one. the whole thing is giving organized 🎀
Status of This Memo 🌸
this is an Internet Standards Track document 💅
it's a product of the Internet Engineering Task Force (IETF), and it represents the consensus of the IETF community. it got public review and was approved for publication by the Internet Engineering Steering Group (IESG). if you want more on Internet Standards, check out Section 2 of RFC 5741.
for the current status, any errata, and how to send feedback, go to http://www.rfc-editor.org/info/rfc5754 🔗
Copyright Notice 💜
the copyright is Copyright (c) 2010 IETF Trust and the persons identified as the document authors, all rights reserved 🫶
this doc is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (http://trustee.ietf.org/license-info) as they stand on the date of publication. please actually read those, bestie, because they explain your rights and restrictions 📜
Code Components pulled out of this document must include Simplified BSD License text, as described in Section 4.e of the Trust Legal Provisions. they're provided without warranty, as the Simplified BSD License describes.
this doc may have material from IETF Documents or IETF Contributions that were published or made publicly available before November 10, 2008. the people who control the copyright in some of that material may never have given the IETF Trust permission to allow changes outside the IETF Standards Process. so unless you get an adequate license from those copyright holders, this doc can't be modified outside the IETF Standards Process, and derivative works can't be made outside it either. the exceptions are formatting it for publication as an RFC or translating it into languages other than English 🌈
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 ....................................101. Introduction 🦋
okay so this doc specifies the algorithm identifiers and the 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 themselves are defined in [SHS], and reference code is in [RFC4634] ✨
it also specifies the algorithm identifiers and parameters for using SHA-224, SHA-256, SHA-384, and SHA-512 with DSA [DSS], with RSA (RSASSA-PKCS1-v1_5) [RFC3447], and with ECDSA [DSS] 💖
this doc doesn't define any new identifiers. they come from [RFC3874], [RFC4055], and [RFC5758], and the parameters follow the conventions in those docs. that's why there's no Abstract Syntax Notation One (ASN.1) module in here 🙈
quick note: [RFC4231] covers the conventions for the message authentication code (MAC) algorithms, which are 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. it's repeated here for convenience:
AlgorithmIdentifier ::= SEQUENCE {
algorithm OBJECT IDENTIFIER,
parameters ANY DEFINED BY algorithm OPTIONAL }this doc also specifies the SMIMECapabilities attribute values [RFC5751] for each algorithm. the values are for the SMIMECapability field, which is also repeated 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 live 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 live in the DigestedData digest field and the Message Digest authenticated attribute. on top of that, digest values get fed into signature algorithms 🔥
the digest algorithm identifiers use the AlgorithmIdentifier syntax that got elaborated on back in Section 1.
the algorithm field and the SMIMECapabilities attribute are covered in Sections 2.1-2.4, one for each message digest algorithm. Section 3 has some signatures that use the SHA2 algorithms. and for the procedures to compute the digest values (aka DigestInfo), you'll want to check the signature algorithm definitions 🧠
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]. its algorithm identifier 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 at the beginning of Section 2 🧚
the SMIMECapabilities attribute value shows support for SHA-224. it's a SEQUENCE with the capabilityID field holding 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 02 042.2. SHA-256 🦋
the SHA-256 message digest algorithm is defined in [SHS]. its algorithm identifier 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 at the beginning of Section 2 ✨
the SMIMECapabilities attribute value shows support for SHA-256. it's a SEQUENCE with the capabilityID field holding 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 02 012.3. SHA-384 🎀
the SHA-384 message digest algorithm is defined in [SHS]. its algorithm identifier 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 at the beginning of Section 2 💜
the SMIMECapabilities attribute value shows support for SHA-384. it's a SEQUENCE with the capabilityID field holding 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 02 022.4. SHA-512 👑
the SHA-512 message digest algorithm is defined in [SHS]. its algorithm identifier 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 at 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 02 033. Signature Algorithms ⭐
this section covers the conventions that CMS implementations use when they support DSA, RSA, and ECDSA with the SHA2 algorithms 🔥
signature algorithm identifiers live in the SignerInfo signatureAlgorithm field of SignedData. they also live in the SignerInfo signatureAlgorithm field of countersignature attributes 🫶
signature values live in the SignerInfo signature field of SignedData. they also live in the SignerInfo signature field of countersignature attributes 💅
3.1. DSA
okay so DSA, bestie 💖 [RFC3370], Section 3.1, already lays out the rules for DSA with SHA-1: public key algorithm identifiers, parameters, public keys, and signature values. DSA with SHA2 uses those exact same conventions for all four things 🎀 no new drama. DSA MAY be used with SHA-224 and SHA-256. The object identifiers come from [RFC5758] ✨
Now the not-me moment 💀 DSA has not been specified with SHA-384 and SHA-512. They're 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. No parameters, no exceptions, periodt 💅
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 03 023.2. RSA
[RFC3370], Section 3.2, covers RSA with SHA-1 (RSASSA-PKCS1-v1_5) public key algorithm identifiers, parameters, public keys, and signature values 🌸 and RSA with SHA2 algorithms just reuses those same conventions. Same energy, new flavours 🍓 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. So NULL is the rule when you're sending, but if somebody shows up with no parameters at all, you still have to accept it 🫶
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
05 003.3. 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 are included below for convenience, and they're 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. One item, no parameters, very clean 👑
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 03 044. 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. Nothing new to panic about, but those older documents are still the ones to read, so don't skip them 🔥
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📦 where this page comes from
- ietf: rfc5754 2010-01
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