


Network Working Group                                        E. Rescorla
Internet-Draft                                                RTFM, Inc.
Intended status:  Informational                           April 14, 2008
Expires:  October 16, 2008


TLS Elliptic Curve Cipher Suites with SHA-256/384 and AES Galois Counter
                                  Mode
                   draft-ietf-tls-ecc-new-mac-05.txt

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Copyright Notice

   Copyright (C) The IETF Trust (2008).

Abstract

   RFC 4492 describes elliptic curve cipher suites for Transport Layer
   Security (TLS).  However, all those cipher suites use SHA-1 as their
   MAC algorithm.  This document describes sixteen new CipherSuites for
   TLS/DTLS which specify stronger digest algorithms.  Eight use HMAC
   with SHA-256 or SHA-384 and eight use AES in Galois Counter Mode
   (GCM).




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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . . . 3
     1.1.  Conventions Used In This Document . . . . . . . . . . . . . 3
   2.  Cipher Suites . . . . . . . . . . . . . . . . . . . . . . . . . 3
     2.1.  HMAC-based Cipher Suites  . . . . . . . . . . . . . . . . . 3
     2.2.  Galois Counter Mode-based Cipher Suites . . . . . . . . . . 4
   3.  Security Considerations . . . . . . . . . . . . . . . . . . . . 5
   4.  IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 5
   5.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . . 5
   6.  References  . . . . . . . . . . . . . . . . . . . . . . . . . . 5
     6.1.  Normative References  . . . . . . . . . . . . . . . . . . . 5
     6.2.  Informative References  . . . . . . . . . . . . . . . . . . 6
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . . . 6
   Intellectual Property and Copyright Statements  . . . . . . . . . . 8




































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1.  Introduction

   RFC 4492 [RFC4492] describes Elliptic Curve Cryptography (ECC) cipher
   suites for Transport Layer Security (TLS).  However, all of the RFC
   4492 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 which use SHA-256 and SHA-384 rather
   than SHA-1.

   TLS 1.2 [I-D.ietf-tls-rfc4346-bis], 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
   [I-D.ietf-tls-rsa-aes-gcm], provides support for GCM with other key
   establishment methods.

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.  Cipher Suites

   This document defines 8 new cipher suites to be added to TLS.  All
   use Elliptic Curve Cryptography for key exchange and digital
   signature, as defined in RFC 4492.

2.1.  HMAC-based Cipher Suites

   The first eight cipher suites use AES [AES] in CBC [CBC] mode with an
   HMAC-based MAC:

       CipherSuite TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA256  = {0xXX,XX};
       CipherSuite TLS_ECDHE_ECDSA_WITH_AES_256_CBC_SHA384  = {0xXX,XX};
       CipherSuite TLS_ECDH_ECDSA_WITH_AES_128_CBC_SHA256   = {0xXX,XX};
       CipherSuite TLS_ECDH_ECDSA_WITH_AES_256_CBC_SHA384   = {0xXX,XX};
       CipherSuite TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256    = {0xXX,XX};
       CipherSuite TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA384    = {0xXX,XX};
       CipherSuite TLS_ECDH_RSA_WITH_AES_128_CBC_SHA256     = {0xXX,XX};
       CipherSuite TLS_ECDH_RSA_WITH_AES_256_CBC_SHA384     = {0xXX,XX};

   These eight cipher suites are the same as the corresponding cipher
   suites in RFC 4492 (TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA,
   TLS_ECDHE_ECDSA_WITH_AES_256_CBC_SHA,
   TLS_ECDH_ECDSA_WITH_AES_128_CBC_SHA,



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   TLS_ECDH_ECDSA_WITH_AES_256_CBC_SHA,
   TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA,
   TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA,
   TLS_ECDH_RSA_WITH_AES_128_CBC_SHA, and
   TLS_ECDH_RSA_WITH_AES_256_CBC_SHA) except for the hash and PRF
   algorithms, which are SHA-256 and SHA-384 [SHS] as follows.

       Cipher Suite                                MAC          PRF
       ------------                                ---          ---
       TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA256     HMAC-SHA-256 P_SHA256
       TLS_ECDHE_ECDSA_WITH_AES_256_CBC_SHA384     HMAC-SHA-384 P_SHA384
       TLS_ECDH_ECDSA_WITH_AES_128_CBC_SHA256      HMAC-SHA-256 P_SHA256
       TLS_ECDH_ECDSA_WITH_AES_256_CBC_SHA384      HMAC-SHA-384 P_SHA384
       TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256       HMAC-SHA-256 P_SHA256
       TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA384       HMAC-SHA-384 P_SHA384
       TLS_ECDH_RSA_WITH_AES_128_CBC_SHA256        HMAC-SHA-256 P_SHA256
       TLS_ECDH_RSA_WITH_AES_256_CBC_SHA384        HMAC-SHA-384 P_SHA384

2.2.  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  = {0xXX,XX};
       CipherSuite TLS_ECDHE_ECDSA_WITH_AES_256_GCM_SHA384  = {0xXX,XX};
       CipherSuite TLS_ECDH_ECDSA_WITH_AES_128_GCM_SHA256   = {0xXX,XX};
       CipherSuite TLS_ECDH_ECDSA_WITH_AES_256_GCM_SHA384   = {0xXX,XX};
       CipherSuite TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256    = {0xXX,XX};
       CipherSuite TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384    = {0xXX,XX};
       CipherSuite TLS_ECDH_RSA_WITH_AES_128_GCM_SHA256     = {0xXX,XX};
       CipherSuite TLS_ECDH_RSA_WITH_AES_256_GCM_SHA384     = {0xXX,XX};

   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 [I-D.ietf-tls-rsa-aes-gcm].


        Cipher Suite                                PRF
        ------------                                ---
        TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256     P_SHA256
        TLS_ECDHE_ECDSA_WITH_AES_256_GCM_SHA384     P_SHA384
        TLS_ECDH_ECDSA_WITH_AES_128_GCM_SHA256      P_SHA256
        TLS_ECDH_ECDSA_WITH_AES_256_GCM_SHA384      P_SHA384
        TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256       P_SHA256
        TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384       P_SHA384
        TLS_ECDH_RSA_WITH_AES_128_GCM_SHA256        P_SHA256



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        TLS_ECDH_RSA_WITH_AES_256_GCM_SHA384        P_SHA384


3.  Security Considerations

   The security considerations in RFC 4346, RFC 4492, and
   [I-D.ietf-tls-rsa-aes-gcm] apply to this document as well.  In
   addition, as described in [I-D.ietf-tls-rsa-aes-gcm], these cipher
   suites may only be used with TLS 1.2 or greater.


4.  IANA Considerations

   IANA has assigned the following values for these cipher suites:

       CipherSuite TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA256  = {0xXX,XX};
       CipherSuite TLS_ECDHE_ECDSA_WITH_AES_256_CBC_SHA384  = {0xXX,XX};
       CipherSuite TLS_ECDH_ECDSA_WITH_AES_128_CBC_SHA256   = {0xXX,XX};
       CipherSuite TLS_ECDH_ECDSA_WITH_AES_256_CBC_SHA384   = {0xXX,XX};
       CipherSuite TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256    = {0xXX,XX};
       CipherSuite TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA384    = {0xXX,XX};
       CipherSuite TLS_ECDH_RSA_WITH_AES_128_CBC_SHA256     = {0xXX,XX};
       CipherSuite TLS_ECDH_RSA_WITH_AES_256_CBC_SHA384     = {0xXX,XX};
       CipherSuite TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256  = {0xXX,XX};
       CipherSuite TLS_ECDHE_ECDSA_WITH_AES_256_GCM_SHA384  = {0xXX,XX};
       CipherSuite TLS_ECDH_ECDSA_WITH_AES_128_GCM_SHA256   = {0xXX,XX};
       CipherSuite TLS_ECDH_ECDSA_WITH_AES_256_GCM_SHA384   = {0xXX,XX};
       CipherSuite TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256    = {0xXX,XX};
       CipherSuite TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384    = {0xXX,XX};
       CipherSuite TLS_ECDH_RSA_WITH_AES_128_GCM_SHA256     = {0xXX,XX};
       CipherSuite TLS_ECDH_RSA_WITH_AES_256_GCM_SHA384     = {0xXX,XX};


5.  Acknowledgements

   This work was supported by the US Department of Defense.

   David McGrew contributed substantual sections of the GCM nonce text
   as well as providing a review of this document.


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.




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   [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.

   [I-D.ietf-tls-rfc4346-bis]
              Dierks, T. and E. Rescorla, "The Transport Layer Security
              (TLS) Protocol Version 1.2", draft-ietf-tls-rfc4346-bis-10
              (work in progress), March 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.

6.2.  Informative References

   [Wang05]   Wang, X., Yin, Y., and H. Yu, "Finding Collisions in the
              Full SHA-1", CRYPTO 2005, August 2005.

   [I-D.ietf-tls-rsa-aes-gcm]
              Salowey, J., Choudhury, A., and D. McGrew, "AES-GCM Cipher
              Suites for TLS", draft-ietf-tls-rsa-aes-gcm-02 (work in
              progress), February 2008.














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Author's Address

   Eric Rescorla
   RTFM, Inc.
   2064 Edgewood Drive
   Palo Alto  94303
   USA

   Email:  ekr@rtfm.com










































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