One document matched: draft-josefsson-salsa20-tls-00.txt
Network Working Group S. Josefsson
Internet-Draft SJD AB
Intended status: Informational J. Strombergson
Expires: September 18, 2013 Secworks Sweden AB
March 17, 2013
The Salsa20 Stream Cipher for Transport Layer Security (TLS) and
Datagram Transport Layer Security (DTLS)
draft-josefsson-salsa20-tls-00
Abstract
This document describe how the Salsa20 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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This Internet-Draft will expire on September 18, 2013.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Salsa20 Cipher Suites . . . . . . . . . . . . . . . . . . . . 4
3. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 6
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7
5. Security Considerations . . . . . . . . . . . . . . . . . . . 8
6. Normative References . . . . . . . . . . . . . . . . . . . . . 9
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 10
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1. Introduction
This document describe how the Salsa20 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] and in the Datagram
Transport Layer Security (DTLS) version 1.0 [RFC4347], and DTLS
version 1.2 [RFC6347] protocols.
Salsa20 [SALSA20SPEC] 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. The cipher has been designed to minimize risk due to
side channel attacks.
The Salsa20 cipher has trivial initialization sequence and provides
good key agility and good performance over a range of data sizes.
Salsa20 is one of the ciphers selected as part of the eSTREAM
portolio of stream ciphers.
Recent attacks has indicated problems with CBC-mode cipher suites in
TLS/DTLS and problems with the only supported stream cipher (RC4) in
TLS has been known for a long time. While AEAD cipher suites address
these issues, concerns about performance are sometimes raised. DTLS
forbid the use of RC4 because it does not provide random access of
the key stream. The purpose of this document is to provide an
alternative stream cipher for both TLS and DTLS.
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2. Salsa20 Cipher Suites
The following variants of Salsa20 are specified. The variants
provides a range of performance and security that can be selected as
appropriate.
SALSA20R12_128: Salsa20 with 12 rounds and a 128 bit key. This
cipher corresponds to the eSTREAM Salsa20 with 128 bit key.
SALSA20R12_256: Salsa20 with 12 rounds and a 256 bit key. This
cipher corresponds to the eSTREAM Salsa20 with 256 bit key.
SALSA20_256: Salsa20 with 20 rounds and a 256 bit key. This is the
traditional and high security version of Salsa20.
The following ciphersuites are defined:
CipherSuite TLS_RSA_WITH_SALSA20R12_128_SHA256 = {0xTBD, 0xTBD}
CipherSuite TLS_RSA_WITH_SALSA20R12_256_SHA256 = {0xTBD, 0xTBD}
CipherSuite TLS_RSA_WITH_SALSA20_256_SHA256 = {0xTBD, 0xTBD}
CipherSuite TLS_DHE_RSA_WITH_SALSA20R12_128_SHA256 = {0xTBD, 0xTBD}
CipherSuite TLS_DHE_RSA_WITH_SALSA20R12_256_SHA256 = {0xTBD, 0xTBD}
CipherSuite TLS_DHE_RSA_WITH_SALSA20_256_SHA256 = {0xTBD, 0xTBD}
CipherSuite TLS_ECDHE_RSA_WITH_SALSA20R12_128_SHA256 = {0xTBD, 0xTBD}
CipherSuite TLS_ECDHE_RSA_WITH_SALSA20R12_256_SHA256 = {0xTBD, 0xTBD}
CipherSuite TLS_ECDHE_RSA_WITH_SALSA20_256_SHA256 = {0xTBD, 0xTBD}
CipherSuite TLS_ECDHE_ECDSA_WITH_SALSA20R12_128_SHA256 = {0xTBD, 0xTBD}
CipherSuite TLS_ECDHE_ECDSA_WITH_SALSA20R12_256_SHA256 = {0xTBD, 0xTBD}
CipherSuite TLS_ECDHE_ECDSA_WITH_SALSA20_256_SHA256 = {0xTBD, 0xTBD}
CipherSuite TLS_PSK_WITH_SALSA20R12_128_SHA256 = {0xTBD, 0xTBD}
CipherSuite TLS_PSK_WITH_SALSA20R12_256_SHA256 = {0xTBD, 0xTBD}
CipherSuite TLS_PSK_WITH_SALSA20_256_SHA256 = {0xTBD, 0xTBD}
CipherSuite TLS_DHE_PSK_WITH_SALSA20R12_128_SHA256 = {0xTBD, 0xTBD}
CipherSuite TLS_DHE_PSK_WITH_SALSA20R12_256_SHA256 = {0xTBD, 0xTBD}
CipherSuite TLS_DHE_PSK_WITH_SALSA20_256_SHA256 = {0xTBD, 0xTBD}
CipherSuite TLS_RSA_PSK_WITH_SALSA20R12_128_SHA256 = {0xTBD, 0xTBD}
CipherSuite TLS_RSA_PSK_WITH_SALSA20R12_256_SHA256 = {0xTBD, 0xTBD}
CipherSuite TLS_RSA_PSK_WITH_SALSA20_256_SHA256 = {0xTBD, 0xTBD}
CipherSuite TLS_ECDHE_PSK_WITH_SALSA20R12_128_SHA256 = {0xTBD, 0xTBD}
CipherSuite TLS_ECDHE_PSK_WITH_SALSA20R12_256_SHA256 = {0xTBD, 0xTBD}
CipherSuite TLS_ECDHE_PSK_WITH_SALSA20_256_SHA256 = {0xTBD, 0xTBD}
The RSA, DHE_RSA, ECDHE_RSA, ECDHE_ECDSA, PSK, DHE_PSK, RSA_PSK,
ECDHE_PSK key exchanges are performed as defined in RFC 5246, RFC
4492 and RFC 5489.
The hash algorithms and pseudorandom function (PRF) algorithms for
TLS 1.2 SHALL be the HMAC-SHA-256 as the MAC algorithm. The PRF is
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the TLS PRF with SHA-256 as the hash function. [[[XXX: For
performance, we may consider the use UMAC-AES-12 or UMAC-AES-16
instead of HMAC-256, it should provide roughly 5 times better
performance.]]]
PSK cipher suites for TLS are described in RFC 5487 as to SHA-256/384
and RFC 5489 as to ECDHE_PSK.
Because the GenericStreamCipher definition in TLS does not provide
any way to transport the Salsa20 nonce that is required for
functionality and needed to provide the random access property, we
let the output from the stream cipher operation be the concatenation
of the IV and the encrypted data. As a consequence the encrypted
output is a bit longer than the plaintext, similar for AEADs.
[[[XXX: There may be other approaches to address this issue, see
mailing list discussions.]]]
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3. Acknowledgements
Thanks to D. J. Bernstein and Nikos Mavrogiannopoulos for discussion
and suggestions.
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4. IANA Considerations
IANA is requested to allocate the following numbers in the TLS Cipher
Suite Registry:
CipherSuite TLS_RSA_WITH_SALSA20R12_128_SHA256 = {0xTBD, 0xTBD}
CipherSuite TLS_RSA_WITH_SALSA20R12_256_SHA256 = {0xTBD, 0xTBD}
CipherSuite TLS_RSA_WITH_SALSA20_256_SHA256 = {0xTBD, 0xTBD}
CipherSuite TLS_DHE_RSA_WITH_SALSA20R12_128_SHA256 = {0xTBD, 0xTBD}
CipherSuite TLS_DHE_RSA_WITH_SALSA20R12_256_SHA256 = {0xTBD, 0xTBD}
CipherSuite TLS_DHE_RSA_WITH_SALSA20_256_SHA256 = {0xTBD, 0xTBD}
CipherSuite TLS_ECDHE_RSA_WITH_SALSA20R12_128_SHA256 = {0xTBD, 0xTBD}
CipherSuite TLS_ECDHE_RSA_WITH_SALSA20R12_256_SHA256 = {0xTBD, 0xTBD}
CipherSuite TLS_ECDHE_RSA_WITH_SALSA20_256_SHA256 = {0xTBD, 0xTBD}
CipherSuite TLS_ECDHE_ECDSA_WITH_SALSA20R12_128_SHA256 = {0xTBD, 0xTBD}
CipherSuite TLS_ECDHE_ECDSA_WITH_SALSA20R12_256_SHA256 = {0xTBD, 0xTBD}
CipherSuite TLS_ECDHE_ECDSA_WITH_SALSA20_256_SHA256 = {0xTBD, 0xTBD}
CipherSuite TLS_PSK_WITH_SALSA20R12_128_SHA256 = {0xTBD, 0xTBD}
CipherSuite TLS_PSK_WITH_SALSA20R12_256_SHA256 = {0xTBD, 0xTBD}
CipherSuite TLS_PSK_WITH_SALSA20_256_SHA256 = {0xTBD, 0xTBD}
CipherSuite TLS_DHE_PSK_WITH_SALSA20R12_128_SHA256 = {0xTBD, 0xTBD}
CipherSuite TLS_DHE_PSK_WITH_SALSA20R12_256_SHA256 = {0xTBD, 0xTBD}
CipherSuite TLS_DHE_PSK_WITH_SALSA20_256_SHA256 = {0xTBD, 0xTBD}
CipherSuite TLS_RSA_PSK_WITH_SALSA20R12_128_SHA256 = {0xTBD, 0xTBD}
CipherSuite TLS_RSA_PSK_WITH_SALSA20R12_256_SHA256 = {0xTBD, 0xTBD}
CipherSuite TLS_RSA_PSK_WITH_SALSA20_256_SHA256 = {0xTBD, 0xTBD}
CipherSuite TLS_ECDHE_PSK_WITH_SALSA20R12_128_SHA256 = {0xTBD, 0xTBD}
CipherSuite TLS_ECDHE_PSK_WITH_SALSA20R12_256_SHA256 = {0xTBD, 0xTBD}
CipherSuite TLS_ECDHE_PSK_WITH_SALSA20_256_SHA256 = {0xTBD, 0xTBD}
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5. Security Considerations
The reader must consult cryptographic research to find out the
security status of Salsa20. At the time of writing this document,
there are no known weak keys for Salsa20 and no known significant
security problem with Salsa20. For more background, see the eSTREAM
reports.
This document should not introduce any other security considerations
than those that directly follow from any use of the stream cipher
Salsa20 and those that directly follow from introducing any set of
stream cipher suites into TLS and DTLS.
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6. 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.
[RFC6347] Rescorla, E. and N. Modadugu, "Datagram Transport Layer
Security Version 1.2", RFC 6347, January 2012.
[SALSA20SPEC]
Bernstein, D., "Salsa20 specification",
WWW http://cr.yp.to/snuffle/spec.pdf, April 2005.
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Authors' Addresses
Simon Josefsson
SJD AB
Email: simon@josefsson.org
URI: http://josefsson.org/
Joachim Strombergson
Secworks Sweden AB
Email: joachim@secworks.se
URI: http://secworks.se/
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