Internet Engineering Task Force (IETF)
Request for Comments: 5758
Updates: 3279
Category: Standards Track
ISSN: 2070-1721

Q. Dang
NIST
S. Santesson
3xA Security
K. Moriarty
EMC
D. Brown
Certicom Corp.
T. Polk
NIST
January 2010

Internet X.509 Public Key Infrastructure:

Additional Algorithms and Identifiers for DSA and ECDSA

Abstract

This document updates RFC 3279 to specify algorithm identifiers and ASN.1 encoding rules for the Digital Signature Algorithm (DSA) and Elliptic Curve Digital Signature Algorithm (ECDSA) digital signatures when using SHA-224, SHA-256, SHA-384, or SHA-512 as the hashing algorithm. This specification applies to the Internet X.509 Public Key infrastructure (PKI) when digital signatures are used to sign certificates and certificate revocation lists (CRLs). This document also identifies all four SHA2 hash algorithms for use in the Internet X.509 PKI.

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/rfc5758.

Copyright Notice

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. Code 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 Simplified BSD License.

   1. Introduction ....................................................2
   2. Hash Functions ..................................................3
   3. Signature Algorithms ............................................3
      3.1. DSA Signature Algorithm ....................................4
      3.2. ECDSA Signature Algorithm ..................................4
   4. ASN.1 Module ....................................................5
   5. Security Considerations .........................................6
   6. References ......................................................6
      6.1. Normative References .......................................6
      6.2. Informative References .....................................7
   7. Acknowledgements ................................................7

1. Introduction

This specification defines the contents of the signatureAlgorithm, signatureValue, and signature fields within Internet X.509 certificates and CRLs when these objects are signed using DSA or ECDSA with a SHA2 hash algorithm. These fields are more fully described in RFC 5280 [RFC5280]. This document also identifies all four SHA2 hash algorithms for use in the Internet X.509 PKI.

   This document profiles material presented in the "Secure Hash
   Standard" [FIPS180-3], "Public Key Cryptography for the Financial
   Services Industry: The Elliptic Curve Digital Signature Standard
   (ECDSA)" [X9.62], and the "Digital Signature Standard" [FIPS186-3].
   
   This document updates RFC 3279 [RFC3279] Sections 2.1, 2.2.2, and
   2.2.3.  Note that RFC 5480 [RFC5480] updates Sections 2.3.5, 3 (ASN.1
   Module), and 5 (Security Considerations) of RFC 3279.

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. Hash Functions

This section identifies four additional hash algorithms for use with DSA and ECDSA in the Internet X.509 certificate and CRL profile [RFC5280]. SHA-224, SHA-256, SHA-384, and SHA-512 produce a 224-bit, 256-bit, 384-bit, and 512-bit "hash" of the input, respectively, and are fully described in the "Secure Hash Standard" [FIPS180-3].

The listed one-way hash functions are identified by the following object identifiers (OIDs):

   id-sha224  OBJECT IDENTIFIER  ::=  { joint-iso-itu-t(2)
        country(16) us(840) organization(1) gov(101) csor(3)
        nistalgorithm(4) hashalgs(2) 4 }
   
   id-sha256  OBJECT IDENTIFIER  ::=  { joint-iso-itu-t(2)
        country(16) us(840) organization(1) gov(101) csor(3)
        nistalgorithm(4) hashalgs(2) 1 }
   
   id-sha384  OBJECT IDENTIFIER  ::=  { joint-iso-itu-t(2)
        country(16) us(840) organization(1) gov(101) csor(3)
        nistalgorithm(4) hashalgs(2) 2 }
   
   id-sha512  OBJECT IDENTIFIER  ::=  { joint-iso-itu-t(2)
        country(16) us(840) organization(1) gov(101) csor(3)
        nistalgorithm(4) hashalgs(2) 3 }

When one of these OIDs appears in an AlgorithmIdentifier, all implementations MUST accept both NULL and absent parameters as legal and equivalent encodings.

Conforming certification authority (CA) implementations SHOULD use SHA-224, SHA-256, SHA-384, or SHA-512 when generating certificates or CRLs, but MAY use SHA-1 if they have a stated policy that requires the use of this weaker algorithm.

3. Signature Algorithms

This section identifies OIDs for DSA with SHA-224 and SHA-256 as well as ECDSA with SHA-224, SHA-256, SHA-384, and SHA-512. The contents of the parameters component for each signature algorithm vary; details are provided for each algorithm.

3.1. DSA Signature Algorithm

The DSA is defined in the Digital Signature Standard (DSS) [FIPS186-3]. DSA was developed by the U.S. Government, and can be used in conjunction with a SHA2 hash function such as SHA-224 or SHA-256. DSA is fully described in [FIPS186-3].

When SHA-224 is used, the OID 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 }.

When SHA-256 is used, the OID 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 the id-dsa-with-sha224 or id-dsa-with-sha256 algorithm identifier appears in the algorithm field as an AlgorithmIdentifier, the encoding SHALL omit the parameters field. That is, the AlgorithmIdentifier SHALL be a SEQUENCE of one component, the OID id- dsa-with-sha224 or id-dsa-with-sha256.

Encoding rules for DSA signature values are specified in [RFC3279].

Conforming CA implementations that generate DSA signatures for certificates or CRLs MUST generate such DSA signatures in accordance with all the requirements in Sections 4.1, 4.5, and 4.6 of [FIPS186-3].

Conforming CA implementations that generate DSA signatures for certificates or CRLs MAY generate such DSA signatures in accordance with all the requirements and recommendations in [FIPS186-3], if they have a stated policy that requires conformance to [FIPS186-3].

3.2. ECDSA Signature Algorithm

The Elliptic Curve Digital Signature Algorithm (ECDSA) is defined in "Public Key Cryptography for the Financial Services Industry: The Elliptic Curve Digital Signature Standard (ECDSA)" [X9.62]. The ASN.1 OIDs used to specify that an ECDSA signature was generated using SHA-224, SHA-256, SHA-384, or SHA-512 are, respectively:

   ecdsa-with-SHA224 OBJECT IDENTIFIER ::= { iso(1) member-body(2)
        us(840) ansi-X9-62(10045) signatures(4) ecdsa-with-SHA2(3) 1 }
   
   ecdsa-with-SHA256 OBJECT IDENTIFIER ::= { iso(1) member-body(2)
        us(840) ansi-X9-62(10045) signatures(4) ecdsa-with-SHA2(3) 2 }
   
   ecdsa-with-SHA384 OBJECT IDENTIFIER ::= { iso(1) member-body(2)
        us(840) ansi-X9-62(10045) signatures(4) ecdsa-with-SHA2(3) 3 }
   
   ecdsa-with-SHA512 OBJECT IDENTIFIER ::= { iso(1) member-body(2)
        us(840) ansi-X9-62(10045) signatures(4) ecdsa-with-SHA2(3) 4 }
   
   When the ecdsa-with-SHA224, ecdsa-with-SHA256, ecdsa-with-SHA384, or
   ecdsa-with-SHA512 algorithm identifier appears in the algorithm field
   as an AlgorithmIdentifier, the encoding MUST omit the parameters
   field.  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.

Conforming CA implementations MUST specify the hash algorithm explicitly using the OIDs specified above when encoding ECDSA/SHA2 signatures in certificates and CRLs.

Conforming client implementations that process ECDSA signatures with any of the SHA2 hash algorithms when processing certificates and CRLs MUST recognize the corresponding OIDs specified above.

Encoding rules for ECDSA signature values are specified in RFC 3279 [RFC3279], Section 2.2.3, and RFC 5480 [RFC5480].

Conforming CA implementations that generate ECDSA signatures in certificates or CRLs MUST generate such ECDSA signatures in accordance with all the requirements specified in Sections 7.2 and 7.3 of [X9.62] or with all the requirements specified in Section 4.1.3 of [SEC1].

Conforming CA implementations that ECDSA signatures in certificates or CRLs MAY generate such ECDSA signatures in accordance with all the requirements and recommendations in [X9.62] or [SEC1] if they have a stated policy that requires conformance to [X9.62] or [SEC1].

4. ASN.1 Module

The OIDs of the SHA2 hash algorithms are in the RFC 4055 [RFC4055] ASN.1 module and the OIDs for DSA with SHA-224 and SHA-256 as well as ECDSA with SHA-224, SHA-256, SHA-384, and SHA-512 are defined in the RFC 5480 [RFC5480] ASN.1 module.

5. Security Considerations

NIST has defined appropriate use of the hash functions in terms of the algorithm strengths and expected time frames for secure use in Special Publications (SPs) 800-78-1 [SP800-78-1], 800-57 [SP800-57], and 800-107 [SP800-107]. These documents can be used as guides to choose appropriate key sizes for various security scenarios.

ANSI also provides security considerations for ECDSA in [X9.62]. These security considerations may be used as a guide.

6. References

6.1. Normative References

   [RFC2119]    Bradner, S., "Key words for use in RFCs to Indicate
                Requirement Levels", BCP 14, RFC 2119, March 1997.
   
   [RFC3279]    Bassham, L., Polk, W., and R. Housley, "Algorithms and
                Identifiers for the Internet X.509 Public Key
                Infrastructure Certificate and Certificate Revocation
                List (CRL) Profile", RFC 3279, April 2002.
   
   [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.
   
   [RFC5480]    Turner, S., Brown, D., Yiu, K., Housley, R., and T.
                Polk, "Elliptic Curve Cryptography Subject Public Key
                Information", RFC 5480, March 2009.
   
   [RFC5280]    Cooper, D., Santesson, S., Farrell, S., Boeyen, S.,
                Housley, R., and W. Polk, "Internet X.509 Public Key
                Infrastructure Certificate and Certificate Revocation
                List (CRL) Profile", RFC 5280, May 2008.
   
   [FIPS180-3]  Federal Information Processing Standards Publication
                (FIPS PUB) 180-3, Secure Hash Standard (SHS), October
                2008.
   
   [FIPS186-3]  Federal Information Processing Standards Publication
                (FIPS PUB) 186-3, Digital Signature Standard (DSS), June
                2009.
   
   [SEC1]       Standards for Efficient Cryptography Group (SECG), SEC
                1: Elliptic Curve Cryptography, Version 2.0, 2009.
   
   [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

   [SP800-107]  Quynh Dang, NIST, "Recommendation for Applications Using
                Approved Hash Algorithms", February 2009.
   
   [SP800-78-1] W. Timothy Polk, Donna, F. Dodson, William E. Burr,
                NIST, "Cryptographic Standards and Key Sizes for
                Personal Identity Verification", August 2007.
   
   [SP800-57]   Elaine Barker, William Barker, William E. Burr, NIST,
                "Recommendation for Key Management", August 2005.

7. Acknowledgements

The authors of this document would like to acknowledge great inputs for this document from Alfred Hoenes, Sean Turner, Katrin Hoeper, and many others from IETF community. The authors also appreciate many great revision suggestions from Russ Housley and Paul Hoffman.

Authors' Addresses

Quynh Dang
NIST
100 Bureau Drive, Stop 8930
Gaithersburg, MD 20899-8930
USA

   EMail: quynh.dang@nist.gov

Stefan Santesson
3xA Security (AAA-sec.com)
Bjornstorp 744
247 98 Genarp
Sweden

   EMail: sts@aaa-sec.com

Kathleen M. Moriarty
RSA, The Security Division of EMC
174 Middlesex Turnpike
Bedford, MA 01730
USA

EMail:

          Moriarty_Kathleen@emc.com

Daniel R. L. Brown
Certicom Corp.
5520 Explorer Drive
Mississaug, ON L4W 5L1
USA

EMail:

          dbrown@certicom.com

Tim Polk
NIST
100 Bureau Drive, Stop 8930
Gaithersburg, MD 20899-8930
USA

   EMail: tim.polk@nist.gov