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Network Working Group                                        E. RescorlaRequest for Comments:  5289                                   RTFM, Inc.Category:  Informational                                     August 2008TLS Elliptic Curve Cipher Suites withSHA-256/384 and AES Galois Counter Mode (GCM)Status of This Memo   This memo provides information for the Internet community.  It does   not specify an Internet standard of any kind.  Distribution of this   memo is unlimited.AbstractRFC 4492 describes elliptic curve cipher suites for Transport Layer   Security (TLS).  However, all those cipher suites use HMAC-SHA-1 as   their Message Authentication Code (MAC) algorithm.  This document   describes sixteen new cipher suites for TLS that specify stronger MAC   algorithms.  Eight use Hashed Message Authentication Code (HMAC) with   SHA-256 or SHA-384, and eight use AES in Galois Counter Mode (GCM).Table of Contents1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . . .22.  Conventions Used in This Document . . . . . . . . . . . . . . .23.  Cipher Suites . . . . . . . . . . . . . . . . . . . . . . . . .23.1.  HMAC-Based Cipher Suites  . . . . . . . . . . . . . . . . .23.2.  Galois Counter Mode-Based Cipher Suites . . . . . . . . . .34.  Security Considerations . . . . . . . . . . . . . . . . . . . .35.  IANA Considerations . . . . . . . . . . . . . . . . . . . . . .36.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . .47.  References  . . . . . . . . . . . . . . . . . . . . . . . . . .47.1.  Normative References  . . . . . . . . . . . . . . . . . . .47.2.  Informative References  . . . . . . . . . . . . . . . . . .5Rescorla                     Informational                      [Page 1]

RFC 5289                    TLS ECC New MAC                  August 20081.  IntroductionRFC 4492 [RFC4492] describes Elliptic Curve Cryptography (ECC) cipher   suites for Transport Layer Security (TLS).  However, all of theRFC4492 suites use HMAC-SHA1 as their MAC algorithm.  Due to recent   analytic work on SHA-1 [Wang05], the IETF is gradually moving away   from SHA-1 and towards stronger hash algorithms.  This document   specifies TLS ECC cipher suites that use SHA-256 and SHA-384 [SHS]   rather than SHA-1.   TLS 1.2 [RFC5246], adds support for authenticated encryption with   additional data (AEAD) cipher modes [RFC5116].  This document also   specifies a set of ECC cipher suites using one such mode, Galois   Counter Mode (GCM) [GCM].  Another document [RFC5288] provides   support for GCM with other key establishment methods.2.  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].3.  Cipher Suites   This document defines 16 new cipher suites to be added to TLS.  All   use Elliptic Curve Cryptography for key exchange and digital   signature, as defined inRFC 4492.3.1.  HMAC-Based Cipher Suites   The first eight cipher suites use AES [AES] in Cipher Block Chaining   (CBC) [CBC] mode with an HMAC-based MAC:     CipherSuite TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA256  = {0xC0,0x23};     CipherSuite TLS_ECDHE_ECDSA_WITH_AES_256_CBC_SHA384  = {0xC0,0x24};     CipherSuite TLS_ECDH_ECDSA_WITH_AES_128_CBC_SHA256   = {0xC0,0x25};     CipherSuite TLS_ECDH_ECDSA_WITH_AES_256_CBC_SHA384   = {0xC0,0x26};     CipherSuite TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256    = {0xC0,0x27};     CipherSuite TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA384    = {0xC0,0x28};     CipherSuite TLS_ECDH_RSA_WITH_AES_128_CBC_SHA256     = {0xC0,0x29};     CipherSuite TLS_ECDH_RSA_WITH_AES_256_CBC_SHA384     = {0xC0,0x2A};   These eight cipher suites are the same as the corresponding cipher   suites inRFC 4492 (with names ending in "_SHA" in place of "_SHA256"   or "_SHA384"), except for the MAC and Pseudo Random Function (PRF)   algorithms.Rescorla                     Informational                      [Page 2]

RFC 5289                    TLS ECC New MAC                  August 2008   These SHALL be as follows:   o  For cipher suites ending with _SHA256, the PRF is the TLS PRF      [RFC5246] with SHA-256 as the hash function.  The MAC is HMAC      [RFC2104] with SHA-256 as the hash function.   o  For cipher suites ending with _SHA384, the PRF is the TLS PRF      [RFC5246] with SHA-384 as the hash function.  The MAC is HMAC      [RFC2104] with SHA-384 as the hash function.3.2.  Galois Counter Mode-Based Cipher Suites   The second eight cipher suites use the same asymmetric algorithms as   those in the previous section but use the new authenticated   encryption modes defined in TLS 1.2 with AES in Galois Counter Mode   (GCM) [GCM]:     CipherSuite TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256  = {0xC0,0x2B};     CipherSuite TLS_ECDHE_ECDSA_WITH_AES_256_GCM_SHA384  = {0xC0,0x2C};     CipherSuite TLS_ECDH_ECDSA_WITH_AES_128_GCM_SHA256   = {0xC0,0x2D};     CipherSuite TLS_ECDH_ECDSA_WITH_AES_256_GCM_SHA384   = {0xC0,0x2E};     CipherSuite TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256    = {0xC0,0x2F};     CipherSuite TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384    = {0xC0,0x30};     CipherSuite TLS_ECDH_RSA_WITH_AES_128_GCM_SHA256     = {0xC0,0x31};     CipherSuite TLS_ECDH_RSA_WITH_AES_256_GCM_SHA384     = {0xC0,0x32};   These cipher suites use authenticated encryption with additional data   algorithms AEAD_AES_128_GCM and AEAD_AES_256_GCM described in   [RFC5116].  GCM is used as described in [RFC5288].   The PRFs SHALL be as follows:   o  For cipher suites ending with _SHA256, the PRF is the TLS PRF      [RFC5246] with SHA-256 as the hash function.   o  For cipher suites ending with _SHA384, the PRF is the TLS PRF      [RFC5246] with SHA-384 as the hash function.4.  Security Considerations   The security considerations inRFC 4346,RFC 4492, and [RFC5288]   apply to this document as well.  In addition, as described in   [RFC5288], these cipher suites may only be used with TLS 1.2 or   greater.Rescorla                     Informational                      [Page 3]

RFC 5289                    TLS ECC New MAC                  August 20085.  IANA Considerations   IANA has assigned the following values for these cipher suites:     CipherSuite TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA256  = {0xC0,0x23};     CipherSuite TLS_ECDHE_ECDSA_WITH_AES_256_CBC_SHA384  = {0xC0,0x24};     CipherSuite TLS_ECDH_ECDSA_WITH_AES_128_CBC_SHA256   = {0xC0,0x25};     CipherSuite TLS_ECDH_ECDSA_WITH_AES_256_CBC_SHA384   = {0xC0,0x26};     CipherSuite TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256    = {0xC0,0x27};     CipherSuite TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA384    = {0xC0,0x28};     CipherSuite TLS_ECDH_RSA_WITH_AES_128_CBC_SHA256     = {0xC0,0x29};     CipherSuite TLS_ECDH_RSA_WITH_AES_256_CBC_SHA384     = {0xC0,0x2A};     CipherSuite TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256  = {0xC0,0x2B};     CipherSuite TLS_ECDHE_ECDSA_WITH_AES_256_GCM_SHA384  = {0xC0,0x2C};     CipherSuite TLS_ECDH_ECDSA_WITH_AES_128_GCM_SHA256   = {0xC0,0x2D};     CipherSuite TLS_ECDH_ECDSA_WITH_AES_256_GCM_SHA384   = {0xC0,0x2E};     CipherSuite TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256    = {0xC0,0x2F};     CipherSuite TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384    = {0xC0,0x30};     CipherSuite TLS_ECDH_RSA_WITH_AES_128_GCM_SHA256     = {0xC0,0x31};     CipherSuite TLS_ECDH_RSA_WITH_AES_256_GCM_SHA384     = {0xC0,0x32};6.  Acknowledgements   This work was supported by the US Department of Defense.   David McGrew, Pasi Eronen, and Alfred Hoenes provided reviews of this   document.7.  References7.1.  Normative References   [RFC2104]  Krawczyk, H., Bellare, M., and R. Canetti, "HMAC: Keyed-              Hashing for Message Authentication",RFC 2104,              February 1997.   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate              Requirement Levels",BCP 14,RFC 2119, March 1997.   [RFC4492]  Blake-Wilson, S., Bolyard, N., Gupta, V., Hawk, C., and B.              Moeller, "Elliptic Curve Cryptography (ECC) Cipher Suites              for Transport Layer Security (TLS)",RFC 4492, May 2006.   [RFC5116]  McGrew, D., "An Interface and Algorithms for Authenticated              Encryption",RFC 5116, January 2008.   [RFC5246]  Dierks, T. and E. Rescorla, "The Transport Layer Security              (TLS) Protocol Version 1.2",RFC 5246, August 2008.Rescorla                     Informational                      [Page 4]

RFC 5289                    TLS ECC New MAC                  August 2008   [RFC5288]  Salowey, J., Choudhury, A., and D. McGrew, "AES-GCM Cipher              Suites for TLS",RFC 5288, August 2008.   [AES]      National Institute of Standards and Technology,              "Specification for the Advanced Encryption Standard              (AES)", FIPS 197, November 2001.   [SHS]      National Institute of Standards and Technology, "Secure              Hash Standard", FIPS 180-2, August 2002.   [CBC]      National Institute of Standards and Technology,              "Recommendation for Block Cipher Modes of Operation -              Methods and Techniques", SP 800-38A, December 2001.   [GCM]      National Institute of Standards and Technology,              "Recommendation for Block Cipher Modes of Operation:              Galois/Counter Mode (GCM) for Confidentiality and              Authentication", SP 800-38D, November 2007.7.2.  Informative References   [Wang05]   Wang, X., Yin, Y., and H. Yu, "Finding Collisions in the              Full SHA-1", CRYPTO 2005, August 2005.Author's Address   Eric Rescorla   RTFM, Inc.   2064 Edgewood Drive   Palo Alto  94303   USA   EMail:  ekr@rtfm.comRescorla                     Informational                      [Page 5]

RFC 5289                    TLS ECC New MAC                  August 2008Full Copyright Statement   Copyright (C) The IETF Trust (2008).   This document is subject to the rights, licenses and restrictions   contained inBCP 78, and except as set forth therein, the authors   retain all their rights.   This document and the information contained herein are provided on an   "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS   OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND   THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS   OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF   THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED   WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.Intellectual Property   The IETF takes no position regarding the validity or scope of any   Intellectual Property Rights or other rights that might be claimed to   pertain to the implementation or use of the technology described in   this document or the extent to which any license under such rights   might or might not be available; nor does it represent that it has   made any independent effort to identify any such rights.  Information   on the procedures with respect to rights in RFC documents can be   found inBCP 78 andBCP 79.   Copies of IPR disclosures made to the IETF Secretariat and any   assurances of licenses to be made available, or the result of an   attempt made to obtain a general license or permission for the use of   such proprietary rights by implementers or users of this   specification can be obtained from the IETF on-line IPR repository athttp://www.ietf.org/ipr.   The IETF invites any interested party to bring to its attention any   copyrights, patents or patent applications, or other proprietary   rights that may cover technology that may be required to implement   this standard.  Please address the information to the IETF at   ietf-ipr@ietf.org.Rescorla                     Informational                      [Page 6]