S/MIME WG Sean Turner,Network Working Group S. Turner Request for Comments: 5754 IECAIntended Status: Standard TrackUpdates: 3370(once approved) Expires: July 16,December 2009 Category: Standards Track Using SHA2 Algorithms with Cryptographic Message Syntaxdraft-ietf-smime-sha2-11.txt Status of this MemoAbstract ThisInternet-Draft is submitted to IETF in full conformancedocument describes the conventions for using the Secure Hash Algorithm (SHA) message digest algorithms (SHA-224, SHA-256, SHA-384, SHA-512) with theprovisions of BCP 78Cryptographic Message Syntax (CMS). It also describes the conventions for using these algorithms with the CMS andBCP 79. Internet-Drafts are working documentsthe 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 document specifies an Internet standards track protocol for the InternetEngineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet- Drafts. Internet-Drafts are draft documents validcommunity, and requests discussion and suggestions fora maximumimprovements. Please refer to the current edition ofsix monthsthe "Internet Official Protocol Standards" (STD 1) for the standardization state andmay be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." The liststatus ofcurrent Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html This Internet-Draft will expire on July 16, 2009.this protocol. Distribution of this memo is unlimited. Copyright Notice Copyright (c) 2009 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (http://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document.AbstractCode Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the BSD License. This documentdescribesmay contain material from IETF Documents or IETF Contributions published or made publicly available before November 10, 2008. The person(s) controlling theconventions for usingcopyright in some of this material may not have granted theSecure Hash Algorithm (SHA) message digest algorithms (SHA-224, SHA-256, SHA-384, SHA-512) withIETF Trust theCryptographic Message Syntax (CMS). It also describesright to allow modifications of such material outside theconventions for using these algorithms with CMS andIETF Standards Process. Without obtaining an adequate license from theDigital Signature Algorithm (DSA), Rivest Shamir Adleman (RSA), and Elliptic Curve DSA (ECDSA) signature algorithms. Further, it provides SMIMECapabilities attribute values for each algorithm. Conventions usedperson(s) controlling the copyright in such materials, this documentThe key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY",may not be modified outside the IETF Standards Process, and"OPTIONAL" in this document are toderivative works of it may not beinterpreted as described in [RFC2119].created outside the IETF Standards Process, except to format it for publication as an RFC or to translate it into languages other than English. Table of Contents 1.Introduction...................................................2Introduction ....................................................2 1.1. Conventions Used in This Document ..........................3 2. Message DigestAlgorithms......................................3Algorithms .......................................3 2.1.SHA-224...................................................4SHA-224 ....................................................4 2.2.SHA-256...................................................5SHA-256 ....................................................4 2.3.SHA-384...................................................5SHA-384 ....................................................5 2.4.SHA-512...................................................5SHA-512 ....................................................5 3. SignatureAlgorithms...........................................6Algorithms ............................................5 3.1.DSA.......................................................6DSA ........................................................6 3.2.RSA.......................................................7RSA ........................................................7 3.3.ECDSA.....................................................8ECDSA ......................................................8 4. SecurityConsiderations........................................9Considerations .........................................9 5.IANA Considerations............................................9 6. References....................................................10 6.1.References ......................................................9 5.1. NormativeReferences.....................................10 6.2.References .......................................9 5.2. InformativeReferences...................................11References ....................................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)[RFC3852].[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[ECCADD].[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:HMACHashed 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[RFCTBD1][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.LaterLater, the OPTIONAL was recovered via a defect report, but by then many people thought that algorithm parameters were mandatory. Because of thishistoryhistory, 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[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].[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 DERencodingencodings 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[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)(RSASSA-PKCS1-v1_5) [RFC3447] MAY be used with SHA-224, SHA-256, SHA-384, orSHA- 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 DERencodingencodings 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[RFC5753], Section 2.1, specifies the conventions for ECDSA withSHA-1SHA-* (where * is 1, 224, 256, 384, or 512) 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 objectidentifiersidentifiers, which are included below for convenience, are taken from[ECCADD].[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-SHA384ecdsa-with-SHA384, orecdsa-with-SHA512.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 DERencodingencodings 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],[RFC5753], and[ECCADD][RFC5758] 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.References6.1.5.1. 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.June 2009. [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC2119.2119, March 1997. [RFC3370] Housley, R., "Cryptographic Message Syntax (CMS) Algorithms", RFC 3370, August 2002. [RFC3447]Kaliski, B. andJonsson, J.Jonssonand B. Kaliski, "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-bitOne WayOne-way Hash Function: SHA-224", RFC3874.3874, 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", RFC4055.4055, June 2005.[RFCTBD1][RFC5652] Housley, R., "Cryptographic Message Syntax (CMS)", RFC 5652, September 2009. [RFC5751] Ramsdell,B.,B. and S. Turner,"S/MIME"Secure/Multipurpose Internet Mail Extensions (S/MIME) Version 3.2 Message Specification",draft-ietf-smime-3851bis-08.txt, work-in- progress. //* RFC EDITOR: Note replace the above TBD1 with theRFC# for draft- ietf-smime-3851bis-08.txt. *// [RFCTBD2]5751, December 2009. [RFC5753] Turner,S.,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 theRFC#5753, December 2009. [RFC5758] Dang, Q., Santesson, S., Moriarty, K., Brown, D., and T. Polk, "Internet X.509 Public Key Infrastructure: Additional Algorithms and Identifiers fordraft- ietf-smime-3278bis-05.txt. *//DSA and ECDSA", RFC 5758, December 2009. [SHS] National Institute of Standards and Technology (NIST), FIPS Publication 180-3: Secure Hash Standard, October 2008.6.2.5.2. Informative References [RFC4231] Nystrom,A.M., "Identifiers and Test Vectors for HMAC-SHA- 224, HMAC-SHA-256, HMAC-SHA-384, and HMAC-SHA-512",RFC4231.RFC 4231, December 2005. [RFC4634]Eastlake, D.,Eastlake 3rd, D. and T. Hansen, "US Secure Hash Algorithms (SHA and HMAC-SHA)", RFC 4634, July 2006. Author'sAddressesAddress Sean Turner IECA, Inc. 3057 Nutley Street, Suite 106 Fairfax, VA 22031 USA EMail: turners@ieca.com