The ChaCha Stream Cipher for Transport Layer Security
draft-mavrogiannopoulos-chacha-tls-00
The information below is for an old version of the document.
| Document | Type | Active Internet-Draft (individual) | |
|---|---|---|---|
| Authors | Nikos Mavrogiannopoulos , Joachim Strombergson , Simon Josefsson | ||
| Last updated | 2013-12-06 | ||
| Replaced by | draft-ietf-tls-chacha20-poly1305, draft-ietf-tls-chacha20-poly1305, RFC 7905 | ||
| Stream | (None) | ||
| Formats | plain text xml htmlized pdfized bibtex | ||
| Stream | Stream state | (No stream defined) | |
| Consensus boilerplate | Unknown | ||
| RFC Editor Note | (None) | ||
| IESG | IESG state | I-D Exists | |
| Telechat date | (None) | ||
| Responsible AD | (None) | ||
| Send notices to | (None) |
draft-mavrogiannopoulos-chacha-tls-00
Network Working Group N. Mavrogiannopoulos
Internet-Draft Red Hat
Intended status: Informational J. Strombergson
Expires: June 9, 2014 Secworks Sweden AB
S. Josefsson
SJD AB
December 6, 2013
The ChaCha Stream Cipher for Transport Layer Security
draft-mavrogiannopoulos-chacha-tls-00
Abstract
This document describe how the Chacha stream cipher can be used in
the Transport Layer Security (TLS) and Datagram Transport Layer
Security (DTLS) protocols.
Status of this Memo
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provisions of BCP 78 and BCP 79.
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material or to cite them other than as "work in progress."
This Internet-Draft will expire on June 9, 2014.
Copyright Notice
Copyright (c) 2013 IETF Trust and the persons identified as the
document authors. All rights reserved.
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described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Chacha Cipher Suites . . . . . . . . . . . . . . . . . . . . . 4
2.1. Chacha Cipher Suites with HMAC-SHA1 . . . . . . . . . . . 4
3. The TLS GenericStreamCipher . . . . . . . . . . . . . . . . . 5
4. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 6
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7
6. Security Considerations . . . . . . . . . . . . . . . . . . . 8
7. References . . . . . . . . . . . . . . . . . . . . . . . . . . 9
7.1. Normative References . . . . . . . . . . . . . . . . . . . 9
7.2. Informative References . . . . . . . . . . . . . . . . . . 9
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 11
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1. Introduction
This document describe how the Chacha stream cipher can be used in
the Transport Layer Security (TLS) version 1.0 [RFC2246], TLS version
1.1 [RFC4346], and TLS version 1.2 [RFC5246] protocols, as well as in
the Datagram Transport Layer Security (DTLS) versions 1.0 [RFC4347]
and 1.2 [RFC6347]. It can also be used with Secure Sockets Layer
(SSL) version 3.0 [RFC6101].
Chacha [CHACHASPEC] is a stream cipher that has been designed for
high performance in software implementations. The cipher has compact
implementation and uses few resources and inexpensive operations that
makes it suitable for implementation on a wide range of
architectures. It has been designed to prevent leakage of
information through side channel analysis, has a simple and fast key
setup and provides good overall performance. It is a variant of
Salsa20 [SALSA20SPEC] which is one of the selected ciphers in the
eSTREAM portfolio [ESTREAM].
Recent attacks [CBC-ATTACK] have indicated problems with CBC-mode
cipher suites in TLS and DTLS as well as issues with the only
supported stream cipher (RC4) [RC4-ATTACK]. While the existing AEAD
ciphersuites address these issues, concerns about their performance,
on general purpose CPUs, are sometimes raised [AEAD-PERFORMANCE].
Moreover, the DTLS protocol cannot take advantage of the fast RC4
stream cipher because it does not provide random access in the key
stream.
Therefore, a new stream cipher to replace RC4 and address all the
previous issues is needed. It is the purpose of this document to
describe a secure stream cipher for both TLS and DTLS that is
comparable to RC4 in speed on a wide range of platforms.
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2. Chacha Cipher Suites
The variant of Chacha used in this draft is Chacha with 20 rounds and
a 256 bit key. This is the conservative with respect to security
variant of the Chacha family. Test vectors for this cipher can be
found at [I-D.strombergson-chacha-test-vectors].
In the next sections different ciphersuites are defined that utilize
the Chacha cipher combined with various MAC methods.
In all cases, the pseudorandom function (PRF) for TLS 1.2 is the TLS
PRF with SHA-256 as the hash function. When used with TLS versions
prior to 1.2, the PRF is calculated as specified in the appropriate
version of the TLS specification.
2.1. Chacha Cipher Suites with HMAC-SHA1
The following CipherSuites are defined: (note that the third column
contains the suggested to IANA ciphersuite numbers)
TLS_RSA_WITH_CHACHA_SHA1 = {0xTBD, 0xTBD} {0xE5, 0x00}
TLS_ECDHE_RSA_WITH_CHACHA_SHA1 = {0xTBD, 0xTBD} {0xE5, 0x01}
TLS_ECDHE_ECDSA_WITH_CHACHA_SHA1 = {0xTBD, 0xTBD} {0xE5, 0x02}
TLS_PSK_WITH_CHACHA_SHA1 = {0xTBD, 0xTBD} {0xE5, 0x03}
TLS_ECDHE_PSK_WITH_CHACHA_SHA1 = {0xTBD, 0xTBD} {0xE5, 0x04}
TLS_RSA_PSK_WITH_CHACHA_SHA1 = {0xTBD, 0xTBD} {0xE5, 0x05}
TLS_DHE_PSK_WITH_CHACHA_SHA1 = {0xTBD, 0xTBD} {0xE5, 0x06}
TLS_DHE_RSA_WITH_CHACHA_SHA1 = {0xTBD, 0xTBD} {0xE5, 0x07}
Note that Chacha requires a 64-bit nonce. That nonce is updated on
the encryption of every TLS record, and is set to be the 64-bit TLS
record sequence number. In case of DTLS the 64-bit nonce is formed
as the concatenation of the 16-bit epoch with the 48-bit sequence
number.
The RSA, DHE_RSA, ECDHE_RSA, ECDHE_ECDSA, PSK, DHE_PSK, RSA_PSK,
ECDHE_PSK key exchanges are performed as defined in [RFC5246],
[RFC4492], and [RFC5489].
The MAC algorithm used in the ciphersuites above is HMAC-SHA1
[RFC6234].
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3. The TLS GenericStreamCipher
The ciphersuites defined in this document differ from the TLS RC4
ciphersuites that have been the basis for the definition of
GenericStreamCipher. Unlike RC4, Chacha requires a nonce per record.
This however, does not affect the description of the
GenericStreamCipher if one assumes that a nonce is optional and
depends on the cipher's characteristics (in that case RC4 uses a 0
byte nonce, and Chacha an 8-byte nonce).
As specified in TLS [RFC5246] the MAC is computed before encryption
and the stream cipher encrypts the entire block, including the MAC.
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4. Acknowledgements
The authors would like to thank Zooko Wilcox-OHearn and Samuel Neves
for suggestions that led to this draft.
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5. IANA Considerations
IANA is requested to allocate the following numbers in the TLS Cipher
Suite Registry (note that the third column contains the suggested
ciphersuite numbers):
TLS_RSA_WITH_CHACHA_SHA1 = {0xTBD, 0xTBD} {0xE5, 0x00}
TLS_ECDHE_RSA_WITH_CHACHA_SHA1 = {0xTBD, 0xTBD} {0xE5, 0x01}
TLS_ECDHE_ECDSA_WITH_CHACHA_SHA1 = {0xTBD, 0xTBD} {0xE5, 0x02}
TLS_PSK_WITH_CHACHA_SHA1 = {0xTBD, 0xTBD} {0xE5, 0x03}
TLS_ECDHE_PSK_WITH_CHACHA_SHA1 = {0xTBD, 0xTBD} {0xE5, 0x04}
TLS_RSA_PSK_WITH_CHACHA_SHA1 = {0xTBD, 0xTBD} {0xE5, 0x05}
TLS_DHE_PSK_WITH_CHACHA_SHA1 = {0xTBD, 0xTBD} {0xE5, 0x06}
TLS_DHE_RSA_WITH_CHACHA_SHA1 = {0xTBD, 0xTBD} {0xE5, 0x07}
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6. Security Considerations
Chacha follows the same basic principle as Salsa20, a cipher with
significant security review [SALSA20-SECURITY][ESTREAM]. At the time
of writing this document, there are no known significant security
problems with either cipher, and Chacha is shown to be more resistant
in certain attacks than Salsa20 [SALSA20-ATTACK]. Furthermore Chacha
was used as the core of the BLAKE hash function, a SHA3 finalist,
that had received considerable cryptanalytic attention [NIST-SHA3].
This document should not introduce any other security considerations
than those that directly follow from any use of the stream cipher
Chacha and those that directly follow from introducing any set of
stream cipher suites into TLS and DTLS.
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7. References
7.1. Normative References
[RFC2246] Dierks, T. and C. Allen, "The TLS Protocol Version 1.0",
RFC 2246, January 1999.
[RFC4346] Dierks, T. and E. Rescorla, "The Transport Layer Security
(TLS) Protocol Version 1.1", RFC 4346, April 2006.
[RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer Security
(TLS) Protocol Version 1.2", RFC 5246, August 2008.
[RFC4347] Rescorla, E. and N. Modadugu, "Datagram Transport Layer
Security", RFC 4347, April 2006.
[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.
[RFC5489] Badra, M. and I. Hajjeh, "ECDHE_PSK Cipher Suites for
Transport Layer Security (TLS)", RFC 5489, March 2009.
[RFC6347] Rescorla, E. and N. Modadugu, "Datagram Transport Layer
Security Version 1.2", RFC 6347, January 2012.
[RFC6234] Eastlake, D. and T. Hansen, "US Secure Hash Algorithms
(SHA and SHA-based HMAC and HKDF)", RFC 6234, May 2011.
[CHACHASPEC]
Bernstein, D., "Chacha, a variant of Salsa20",
WWW http://cr.yp.to/chacha/chacha-20080128.pdf,
January 2008.
7.2. Informative References
[I-D.strombergson-chacha-test-vectors]
Strombergson, J., "Test Vectors for the Stream Cipher
ChaCha", draft-strombergson-chacha-test-vectors-00 (work
in progress), October 2013.
[SALSA20SPEC]
Bernstein, D., "Salsa20 specification",
WWW http://cr.yp.to/snuffle/spec.pdf, April 2005.
[RFC6101] Freier, A., Karlton, P., and P. Kocher, "The Secure
Sockets Layer (SSL) Protocol Version 3.0", RFC 6101,
August 2011.
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[SALSA20-SECURITY]
Bernstein, D., "Salsa20 security",
WWW http://cr.yp.to/snuffle/security.pdf, April 2005.
[ESTREAM] Babbage, S., DeCanniere, C., Cantenaut, A., Cid, C.,
Gilbert, H., Johansson, T., Parker, M., Preneel, B.,
Rijmen, V., and M. Robshaw, "The eSTREAM Portfolio (rev.
1)", WWW http://www.ecrypt.eu.org/stream/finallist.html,
September 2008.
[CBC-ATTACK]
AlFardan, N. and K. Paterson, "Lucky Thirteen: Breaking
the TLS and DTLS Record Protocols", IEEE Symposium on
Security and Privacy , 2013.
[RC4-ATTACK]
Isobe, T., Ohigashi, T., Watanabe, Y., and M. Morii, "Full
Plaintext Recovery Attack on Broadcast RC4", International
Workshop on Fast Software Encryption , 2013.
[AEAD-PERFORMANCE]
Krovetz, T. and P. Rogaway, "The Software Performance of
Authenticated-Encryption Modes", International Workshop on
Fast Software Encryption , 2011.
[SALSA20-ATTACK]
Aumasson, J-P., Fischer, S., Khazaei, S., Meier, W., and
C. Rechberger, "New Features of Latin Dances: Analysis of
Salsa, ChaCha, and Rumba",
WWW http://eprint.iacr.org/2007/472.pdf, 2007.
[VLSI-IMPL]
Henzen, L., Carbognani, F., and W. Fichtner, "VLSI
hardware evaluation of the stream ciphers Salsa20 and
ChaCha, and the compression function Rumba", 2008.
[NIST-SHA3]
Chang, S., Burr, W., Kelsey, J., Paul, S., and L. Bassham,
"Third-Round Report of the SHA-3 Cryptographic Hash
Algorithm Competition",
WWW http://dx.doi.org/10.6028/NIST.IR.7896, 2012.
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Authors' Addresses
Nikos Mavrogiannopoulos
Red Hat
Email: nmav@redhat.com
Joachim Strombergson
Secworks Sweden AB
Email: joachim@secworks.se
URI: http://secworks.se/
Simon Josefsson
SJD AB
Email: simon@josefsson.org
URI: http://josefsson.org/
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