Pre-Shared Key Cipher Suites for TLS with SHA-256/384 and AES Galois Counter Mode
RFC 5487

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Network Working Group                                           M. Badra
Request for Comments: 5487                         CNRS/LIMOS Laboratory
Category: Standards Track                                     March 2009

               Pre-Shared Key Cipher Suites for TLS with
                SHA-256/384 and AES Galois Counter Mode

Status of This Memo

   This document specifies an Internet standards track protocol for the
   Internet community, and requests discussion and suggestions for
   improvements.  Please refer to the current edition of the "Internet
   Official Protocol Standards" (STD 1) for the standardization state
   and status of this protocol.  Distribution of this memo is unlimited.

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Abstract

   RFC 4279 and RFC 4785 describe pre-shared key cipher suites for
   Transport Layer Security (TLS).  However, all those cipher suites use
   SHA-1 in their Message Authentication Code (MAC) algorithm.  This
   document describes a set of pre-shared key cipher suites for TLS that
   uses stronger digest algorithms (i.e., SHA-256 or SHA-384) and
   another set that uses the Advanced Encryption Standard (AES) in
   Galois Counter Mode (GCM).

Badra                       Standards Track                     [Page 1]
RFC 5487              TLS PSK New MAC and AES-GCM             March 2009

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . . . 2
     1.1.  Applicability Statement . . . . . . . . . . . . . . . . . . 3
     1.2.  Conventions Used in This Document . . . . . . . . . . . . . 3
   2.  PSK, DHE_PSK, and RSA_PSK Key Exchange Algorithms with
       AES-GCM . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
   3.  PSK, DHE_PSK, and RSA_PSK Key Exchange with SHA-256/384 . . . . 4
     3.1.  PSK Key Exchange Algorithm with SHA-256/384 . . . . . . . . 4
     3.2.  DHE_PSK Key Exchange Algorithm with SHA-256/384 . . . . . . 5
     3.3.  RSA_PSK Key Exchange Algorithm with SHA-256/384 . . . . . . 5
   4.  Security Considerations . . . . . . . . . . . . . . . . . . . . 5
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 5
   6.  Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . 6
   7.  References  . . . . . . . . . . . . . . . . . . . . . . . . . . 6
     7.1.  Normative References  . . . . . . . . . . . . . . . . . . . 6
     7.2.  Informative References  . . . . . . . . . . . . . . . . . . 7

1.  Introduction

   The benefits of pre-shared symmetric-key vs. public-/private-key pair
   based authentication for the key exchange in TLS have been explained
   in the Introduction of [RFC4279].  This document leverages the
   already defined algorithms for the application of newer, generally
   regarded stronger, cryptographic primitives and building blocks.

   TLS 1.2 [RFC5246] adds support for authenticated encryption with
   additional data (AEAD) cipher modes [RFC5116].  This document
   describes the use of Advanced Encryption Standard [AES] in Galois
   Counter Mode [GCM] (AES-GCM) with various pre-shared key (PSK)
   authenticated key exchange mechanisms ([RFC4279] and [RFC4785]) in
   cipher suites for TLS.

   This document also specifies PSK cipher suites for TLS that replace
   SHA-1 by SHA-256 or SHA-384 [SHS].  RFC 4279 [RFC4279] and RFC 4785
   [RFC4785] describe PSK cipher suites for TLS.  However, all of the
   RFC 4279 and the RFC 4785 cipher 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.

   Related TLS cipher suites with key exchange algorithms that are
   authenticated using public/private key pairs have recently been
   specified:

   o  RSA-, DSS-, and Diffie-Hellman-based cipher suites in [RFC5288],
      and