--- /dev/null
+TLS Working Group Mohamad Badra
+Internet Draft LIMOS Laboratory
+Intended status: Informational April 2, 2008
+Expires: October 2008
+
+
+
+ ECDHE_PSK Ciphersuites for Transport Layer Security (TLS)
+ draft-ietf-tls-ecdhe-psk-01.txt
+
+
+Status of this Memo
+
+ By submitting this Internet-Draft, each author represents that any
+ applicable patent or other IPR claims of which he or she is aware
+ have been or will be disclosed, and any of which he or she becomes
+ aware will be disclosed, in accordance with Section 6 of BCP 79.
+
+ Internet-Drafts are working documents of the Internet Engineering
+ 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 valid for a maximum of six months
+ and may 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 list of current 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 October 2, 2008.
+
+Copyright Notice
+
+ Copyright (C) The IETF Trust (2008).
+
+Abstract
+
+ This document extends RFC 4279, RFC 4492 and RFC 4785, and specifies
+ a set of ciphersuites that use a pre-shared key (PSK) to authenticate
+ an Elliptic Curve Diffie-Hellman exchange (ECDH). These ciphersuites
+ provide Perfect Forward Secrecy (PFS).
+
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+Table of Contents
+
+ 1. Introduction...................................................3
+ 1.1. Conventions used in this document.........................3
+ 2. ECDHE_PSK Key Exchange Algorithm...............................3
+ 3. ECDHE_PSK Key Exchange Algorithm with NULL Encryption..........5
+ 4. Security Considerations........................................5
+ 5. IANA Considerations............................................5
+ 6. Acknowledgments................................................5
+ 7. References.....................................................5
+ 7.1. Normative References......................................5
+ Author's Addresses................................................6
+ Intellectual Property Statement...................................6
+ Disclaimer of Validity............................................6
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+1. Introduction
+
+ RFC 4279 specifies ciphersuites for supporting TLS using pre-shared
+ symmetric keys and they (a) use only symmetric key operations for
+ authentication, (b) use a Diffie-Hellman exchange authenticated with
+ a pre-shared key, or (c) combines public key authentication of the
+ server with pre-shared key authentication of the client.
+
+ RFC 4785 specifies authentication-only ciphersuites (with no
+ encryption). These ciphersuites are useful when authentication and
+ integrity protection is desired, but confidentiality is not needed or
+ not permitted.
+
+ RFC 4492 defines a set of ECC-based ciphersuites for TLS and
+ describes the use of ECC certificates for client authentication. In
+ particular, it specifies the use of Elliptic Curve Diffie-Hellman
+ (ECDH) key agreement in a TLS handshake and the use of Elliptic Curve
+ Digital Signature Algorithm (ECDSA) as a new authentication
+ mechanism.
+
+ This document specifies a set of ciphersuites that use a PSK to
+ authenticate an ECDH exchange. These ciphersuites provide Perfect
+ Forward Secrecy. One of these ciphersuite provides authentication-
+ only.
+
+ The reader is expected to become familiar with RFC 4279, RFC 4492,
+ and RFC 4785 prior to studying this document.
+
+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. ECDHE_PSK Key Exchange Algorithm
+
+ The ciphersuites in this section match the ciphersuites defined in
+ [RFC4279], except that they use an Elliptic Curve Diffie-Hellman
+ exchange [RFC4492] authenticated with a PSK. They are defined as
+ follow:
+
+ CipherSuite Key Exchange Cipher Hash
+
+ TLS_ECDHE_PSK_WITH_RC4_128_SHA ECDHE_PSK RC4_128 SHA
+ TLS_ECDHE_PSK_WITH_3DES_EDE_CBC_SHA ECDHE_PSK 3DES_EDE_CBC SHA
+ TLS_ECDHE_PSK_WITH_AES_128_CBC_SHA ECDHE_PSK AES_128_CBC SHA
+ TLS_ECDHE_PSK_WITH_AES_256_CBC_SHA ECDHE_PSK AES_256_CBC SHA
+
+
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+
+ These ciphersuites make use of the EC parameter negotiation mechanism
+ defined in RFC 4492. When the ciphersuites defined in this document
+ are used, the 'ec_diffie_hellman_psk' case inside the
+ ServerKeyExchange and ClientKeyExchange structure MUST be used
+ instead of the 'psk' case defined in [RFC4279] (i.e., the
+ ServerKeyExchange and ClientKeyExchange messages include the Diffie-
+ Hellman parameters). The PSK identity and identity hint fields have
+ the same meaning and encoding specified in [RFC4279] (note that the
+ ServerKeyExchange message is always sent, even if no PSK identity
+ hint is provided).
+
+ The format of the ServerKeyExchange and ClientKeyExchange messages is
+ shown below.
+
+ struct {
+ select (KeyExchangeAlgorithm) {
+ /* other cases for rsa, diffie_hellman, etc. */
+ case ec_diffie_hellman_psk: /* NEW */
+ opaque psk_identity_hint<0..2^16-1>;
+ ServerECDHParams params;
+ };
+ } ServerKeyExchange;
+
+ struct {
+ select (KeyExchangeAlgorithm) {
+ /* other cases for rsa, diffie_hellman, etc. */
+ case ec_diffie_hellman_psk: /* NEW */
+ opaque psk_identity<0..2^16-1>;
+ ClientECDiffieHellmanPublic public;
+ } exchange_keys;
+ } ClientKeyExchange;
+
+ The premaster secret is formed as follows. First, perform an ECDH
+ operation (See section 5.10 of [RFC4492]) to compute the shared
+ secret. Next, concatenate a uint16 containing the length of the
+ shared secret (in octets), the shared secret itself, a uint16
+ containing the length of the PSK (in octets), and the PSK itself.
+
+ This corresponds to the general structure for the premaster secrets
+ (see Note 1 in Section 2 of [RFC4279]), with "other_secret"
+ containing the shared secret:
+
+ struct {
+ opaque other_secret<0..2^16-1>;
+ opaque psk<0..2^16-1>;
+ };
+
+
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+3. ECDHE_PSK Key Exchange Algorithm with NULL Encryption
+
+ The ciphersuite in this section matches the ciphersuites defined in
+ section 2, except that we define a suite with null encryption.
+
+ CipherSuite Key Exchange Cipher Hash
+
+ TLS_ECDHE_PSK_WITH_NULL_SHA ECDHE_PSK NULL SHA
+
+4. Security Considerations
+
+ The security considerations described throughout [RFC4279],
+ [RFC4346], [RFC4492], and [RFC4785] apply here as well.
+
+5. IANA Considerations
+
+ This document defines the following new ciphersuites, whose values
+ are to be assigned from the TLS Cipher Suite registry defined in
+ [RFC4346].
+
+ CipherSuite TLS_ECDHE_PSK_WITH_RC4_128_SHA = { 0xXX, 0xXX };
+ CipherSuite TLS_ECDHE_PSK_WITH_3DES_EDE_CBC_SHA = { 0xXX, 0xXX };
+ CipherSuite TLS_ECDHE_PSK_WITH_AES_128_CBC_SHA = { 0xXX, 0xXX };
+ CipherSuite TLS_ECDHE_PSK_WITH_AES_256_CBC_SHA = { 0xXX, 0xXX };
+ CipherSuite TLS_ECDHE_PSK_WITH_NULL_SHA = { 0xXX, 0xXX };
+
+6. Acknowledgments
+
+ The author would like to thank Bodo Moeller, Simon Josefsson, Uri
+ Blumenthal, Pasi Eronen, Alfred Hoenes, Paul Hoffman, Joseph Salowey,
+ and the TLS mailing list members for their comments on the document.
+
+7. References
+
+7.1. Normative References
+
+ [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
+ Requirement Levels", BCP 14, RFC 2119, March 1997.
+
+ [RFC4279] Eronen, P. and H. Tschofenig, "Pre-Shared Key Ciphersuites
+ for Transport Layer Security (TLS)", RFC 4279, December
+ 2005.
+
+ [RFC4346] Dierks, T. and E. Rescorla, "The TLS Protocol Version 1.1",
+ RFC 4346, April 2006.
+
+
+
+
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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.
+
+ [RFC4785] Blumenthal, U. and P. Goel, "Pre-Shared Key (PSK)
+ Ciphersuites with NULL Encryption for Transport Layer
+ Security (TLS)", RFC 4785, January 2007.
+
+Author's Addresses
+
+ Mohamad Badra
+ LIMOS Laboratory - UMR6158, CNRS
+ France
+
+ Email: badra@isima.fr
+
+
+Intellectual Property Statement
+
+ 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
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+ The IETF invites any interested party to bring to its attention any
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+
+Disclaimer of Validity
+
+ 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
+
+
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+ 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.
+
+Copyright Statement
+
+ Copyright (C) The IETF Trust (2008).
+
+ This document is subject to the rights, licenses and restrictions
+ contained in BCP 78, and except as set forth therein, the authors
+ retain all their rights.
+
+Acknowledgment
+
+ Funding for the RFC Editor function is currently provided by the
+ Internet Society.
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