Internet DRAFT - draft-williams-tls-anon-ecdh-modern-cipher
draft-williams-tls-anon-ecdh-modern-cipher
Network Working Group N. Williams
Internet-Draft Cryptonector
Intended status: Informational March 13, 2014
Expires: September 14, 2014
Anonymous ECDH Ciphersuites with Modern Ciphers and Cipher Modes for
Transport Layer Security (TLS)
draft-williams-tls-anon-ecdh-modern-cipher-01
Abstract
This document requests the registration and allocation of codepoints
for new Transport Layer Security (TLS) ciphersuites with modern
ciphers and cipher modes.
Status of this Memo
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This Internet-Draft will expire on September 14, 2014.
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Table of Contents
1. Introduction and Motivation . . . . . . . . . . . . . . . . . . 3
2. Security Considerations . . . . . . . . . . . . . . . . . . . . 5
3. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 6
4. Normative References . . . . . . . . . . . . . . . . . . . . . 7
Author's Address . . . . . . . . . . . . . . . . . . . . . . . 8
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1. Introduction and Motivation
The Transport Layer Security (TLS) [RFC5246] protocol supports a mode
where key exchange is done without authenticating either the client
nor the server to each other. This is done with ciphersuites using
"anonymous" key agreement algorithms.
TLS ciphersuites are distinct sets of key agreement, server
authentication, data encryption and integrity protection ciphers (and
cipher modes), and pseudo-random functions (PRF). Each set that one
might desire to use must be registered in the IANA TLS ciphersuite
registry.
In recent years new, more modern ciphersuites have been added, but
none with support for Elliptic Curve Diffie-Hellman (ECDH) [RFC4492]
key agreement algorithms. This is problematic because ECDH is more
efficient (both, in terms of compute and network bandwidth
resources), and is generally thought to be more secure than the
alternative. Thus implementations that want anonymous connections
must trade-off security and performance in key agreement for security
and performance in data encryption and integrity protection.
Note that there are good reasons to use anonymous ciphersuites, such
as:
o to protect against passive attackers even when there's no way to
authenticate the peer;
o to protect the identity of the server and/or the identity of the
server as requested by the client in the server name indication
(SNI) TLS extension -- here the client initiates a renegotiation
with the protection of the outer, unauthenticated connection.
This is not an exhaustive list.
This document requests the allocation -and registration- of
ciphersuite codepoints for at least some of the missing ciphersuites,
specifically, the sets of ciphersuites resulting from the cartesian
product of:
o ECDH for key agreement, with ephemeral keys
o no server authentication
o Advanced Encryption Standard (AES) [AES] for data encryption with
the following key sizes:
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* 128-bit keys
* 256-bit keys
o Two block cipher modes for authenticated encryption with
additional data (AEAD):
* Counter with CBC-MAC Mode (CCM) [RFC3610] [CCM]
* Galois Counter Mode [GCM]
o Two hash functions for the TLS PRF:
* SHA256 [RFC4634]
* SHA384 [RFC4634]
filtered such that block cipher key lengths are matched to PRF hash
functions as follows:
o 128-bit key-length ciphers should use SHA256 for the PRF
o 256-bit key-length ciphers should use SHA384 for the PRF
That's four new ciphersuites, see Section 3.
[[anchor1: Should such ciphersuites for Camellia and other
alternative block ciphers also be registered by this document?]]
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2. Security Considerations
There are no new security considerations here beyond those that are
described in each of the documents normatively referenced here.
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3. IANA Considerations
Pursuant to the TLS ciphersuite registry's allocation policy
(Standards Action or Specification Required [RFC2434]), upon IESG
Standards Action publishing this document on the Proposed Standards
track, or acceptance by the RFC-Editor of this document for
publication on the Informational track, the IANA should assign
ciphersuite codepoints to the following ciphersuites, and add them to
the TLS ciphersuite registry:
TLS_ECDH_anon_WITH_AES_128_GCM_SHA256 This is anonymous key
agreement with ephemeral ECDH keys, with AES-128 in GCM mode, and
SHA256 as the hash function for the TLS PRF.
TLS_ECDH_anon_WITH_AES_128_CCM_SHA256 This is anonymous key
agreement with ephemeral ECDH keys, with AES-128 in CCM mode, and
SHA256 as the hash function for the TLS PRF.
TLS_ECDH_anon_WITH_AES_256_GCM_SHA384 This is anonymous key
agreement with ephemeral ECDH keys, with AES-256 in GCM mode, and
SHA384 as the hash function for the TLS PRF.
TLS_ECDH_anon_WITH_AES_256_CCM_SHA384 This is anonymous key
agreement with ephemeral ECDH keys, with AES-256 in CCM mode, and
SHA384 as the hash function for the TLS PRF.
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4. Normative References
[RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer Security
(TLS) Protocol Version 1.2", RFC 5246, August 2008.
[RFC2434] Narten, T. and H. Alvestrand, "Guidelines for Writing an
IANA Considerations Section in RFCs", BCP 26, RFC 2434,
October 1998.
[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.
[RFC3610] Whiting, D., Housley, R., and N. Ferguson, "Counter with
CBC-MAC (CCM)", RFC 3610, September 2003.
[RFC4634] Eastlake, D. and T. Hansen, "US Secure Hash Algorithms
(SHA and HMAC-SHA)", RFC 4634, July 2006.
[AES] National Institute of Standards and Technology,
"Specification for the Advanced Encryption Standard
(AES)", FIPS 197, November 2001.
[GCM] Dworkin, M., "Recommendation for Block Cipher Modes of
Operation: Galois/Counter Mode (GCM) for Confidentiality
and Authentication", Special Publication 800-38D,
November 2007, <http://csrc.nist.gov/publications/
nistpubs/800-38D/SP-800-38D.pdf>.
[CCM] National Institute of Standards and Technology,
"Recommendation for Block Cipher Modes of Operation: The
CCM Mode for Authentication and Confidentiality", SP 800-
38C, May 2004.
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Author's Address
Nicolas Williams
Cryptonector, LLC
Email: nico@cryptonector.com
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