Internet DRAFT - draft-badra-ecdhe-tls-psk
draft-badra-ecdhe-tls-psk
TLS Working Group Mohamad Badra
Internet Draft LIMOS Laboratory
Intended status: Informational February 1, 2008
Expires: July 2008
ECDHE_PSK Ciphersuites for Transport Layer Security (TLS)
draft-badra-ecdhe-tls-psk-03.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 July 31, 2008.
Copyright Notice
Copyright (C) The IETF Trust (2008).
Abstract
This document extends RFC 4279 and RFC 4785 and specifies a set of
ciphersuites that use an Elliptic Curve Diffie-Hellman exchange
authenticated with a pre-shared key. These ciphersuites provide
Perfect Forward Secrecy. It also specifies one authentication-only
ciphersuites (with no encryption). This ciphersuite is useful when
authentication and integrity protection is desired, but
confidentiality is not needed or not permitted.
Badra Expires July 31, 2008 [Page 1]
Internet-Draft ECDHE_PSK Ciphersuites for TLS February 2008
The reader is expected to become familiar with RFC 4279 and RFC 4785
prior to studying this document.
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).
This document specifies a set of ciphersuites that use an Elliptic
Curve Diffie-Hellman exchange authenticated with a pre-shared key.
These ciphersuites provide Perfect Forward Secrecy. This document
also specifies one authentication-only ciphersuites (with no
encryption). This ciphersuite is useful when authentication and
integrity protection is desired, but confidentiality is not needed or
not permitted.
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 pre-shared key. 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
When the ciphersuites defined in this document are used, the
'ec_diffie_hellman_psk' case inside the ServerKeyExchange and
ClientKeyExchange structure is 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
Badra Expires July 31, 2008 [Page 2]
Internet-Draft ECDHE_PSK Ciphersuites for TLS February 2008
identity hint fields MUST have the same meaning 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>;
};
3. 2. ECDHE_PSK Key Exchange Algorithm with NULL Encryption
The ciphersuite in this section matches the ciphersuites defined in
[RFC4785], except that it uses an Elliptic Curve Diffie-Hellman
exchange authenticated with a pre-shared key.
Badra Expires July 31, 2008 [Page 3]
Internet-Draft ECDHE_PSK Ciphersuites for TLS February 2008
CipherSuite Key Exchange Cipher Hash
TLS_ECDHE_PSK_WITH_NULL_SHA ECDHE_PSK NULL SHA
4. Security Considerations
The security considerations described throughout [RFC4346], [RFC4785]
and [RFC4279] 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, 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.
[RFC4346] Dierks, T., Rescorla, E., "The TLS Protocol Version 1.1",
RFC 4346, April 200P.
[RFC4279] Eronen, P. and H. Tschofenig, "Pre-Shared Key Ciphersuites
for Transport Layer Security (TLS)", RFC 4279, December
2005.
[RFC4785] Blumenthal, U., Goel, P., "Pre-Shared Key (PSK)
Ciphersuites with NULL Encryption for Transport Layer
Security (TLS)", RFC 4785, January 2007.
Badra Expires July 31, 2008 [Page 4]
Internet-Draft ECDHE_PSK Ciphersuites for TLS February 2008
[RFC4492] Blake-Wilson, S., Bolyard, N., Gupta, V., Hawk, C.,
Moeller, B., "Elliptic Curve Cryptography (ECC) Cipher
Suites for Transport Layer Security (TLS)", RFC 4492, May
2006.
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
found in BCP 78 and BCP 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 at
http://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.
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
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.
Badra Expires July 31, 2008 [Page 5]
Internet-Draft ECDHE_PSK Ciphersuites for TLS February 2008
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.
Badra Expires July 31, 2008 [Page 6]
