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.

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   This Internet-Draft is submitted in full conformance with the
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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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