Network Working Group S. Josefsson Internet-Draft SJD AB Intended status: Informational J. Strombergson Expires: September 19, 2013 Secworks Sweden AB N. Mavrogiannopoulos KU Leuven March 18, 2013 The Salsa20 Stream Cipher for Transport Layer Security (TLS) and Datagram Transport Layer Security (DTLS) draft-josefsson-salsa20-tls-01 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 This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- Drafts is at http://datatracker.ietf.org/drafts/current/. 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Expires September 19, 2013 [Page 1] Internet-Draft salsa20tls March 2013 the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Salsa20 Cipher Suites . . . . . . . . . . . . . . . . . . . . 4 3. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 6 4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7 5. Security Considerations . . . . . . . . . . . . . . . . . . . 8 6. References . . . . . . . . . . . . . . . . . . . . . . . . . . 9 6.1. Normative References . . . . . . . . . . . . . . . . . . . 9 6.2. Informative References . . . . . . . . . . . . . . . . . . 9 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 11 Josefsson, et al. Expires September 19, 2013 [Page 2] Internet-Draft salsa20tls March 2013 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] 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]. 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 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 [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 AEAD ciphersuites address these issues, concerns about their performance, on general purpose CPUs, are sometimes raised. Moreover, the RC4 cipher could not be used in DTLS because it did not provide random access in the key stream. That allowed no choice of a fast stream cipher in the context of DTLS. The purpose of this document is to provide an alternative stream cipher for both TLS and DTLS that is comparable to RC4 in speed on a wide range of platforms. Josefsson, et al. Expires September 19, 2013 [Page 3] Internet-Draft salsa20tls March 2013 2. Salsa20 Cipher Suites The following variants of Salsa20 are specified. The variants provide a range of performance and security that can be selected as appropriate. SALSA20R12: Salsa20 with 12 rounds and a 256 bit key. This cipher corresponds to the eSTREAM Salsa20 with 256 bit key. SALSA20R20: Salsa20 with 20 rounds and a 256 bit key. This is a higher security variant of Salsa20. The following ciphersuites are defined: CipherSuite TLS_RSA_WITH_SALSA20R12_SHA1 = {0xTBD, 0xTBD} CipherSuite TLS_RSA_WITH_SALSA20R20_SHA1 = {0xTBD, 0xTBD} CipherSuite TLS_DHE_RSA_WITH_SALSA20R12_SHA1 = {0xTBD, 0xTBD} CipherSuite TLS_DHE_RSA_WITH_SALSA20R20_SHA1 = {0xTBD, 0xTBD} CipherSuite TLS_ECDHE_RSA_WITH_SALSA20R12_SHA1 = {0xTBD, 0xTBD} CipherSuite TLS_ECDHE_RSA_WITH_SALSA20R20_SHA1 = {0xTBD, 0xTBD} CipherSuite TLS_ECDHE_ECDSA_WITH_SALSA20R12_SHA1 = {0xTBD, 0xTBD} CipherSuite TLS_ECDHE_ECDSA_WITH_SALSA20R20_SHA1 = {0xTBD, 0xTBD} CipherSuite TLS_PSK_WITH_SALSA20R12_SHA1 = {0xTBD, 0xTBD} CipherSuite TLS_PSK_WITH_SALSA20R20_SHA1 = {0xTBD, 0xTBD} CipherSuite TLS_DHE_PSK_WITH_SALSA20R12_SHA1 = {0xTBD, 0xTBD} CipherSuite TLS_DHE_PSK_WITH_SALSA20R20_SHA1 = {0xTBD, 0xTBD} CipherSuite TLS_RSA_PSK_WITH_SALSA20R12_SHA1 = {0xTBD, 0xTBD} CipherSuite TLS_RSA_PSK_WITH_SALSA20R20_SHA1 = {0xTBD, 0xTBD} CipherSuite TLS_ECDHE_PSK_WITH_SALSA20R12_SHA1 = {0xTBD, 0xTBD} CipherSuite TLS_ECDHE_PSK_WITH_SALSA20R20_SHA1 = {0xTBD, 0xTBD} Note that Salsa20 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. 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 MAC algorithm to use is HMAC-SHA1 [RFC6234]. [[[XXX: For better performance, we consider the use of UMAC-AES-96, UMAC-AES-128 [RFC4418] or Poly1305 instead of HMAC-SHA1.]]] 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. Josefsson, et al. Expires September 19, 2013 [Page 4] Internet-Draft salsa20tls March 2013 PSK cipher suites for TLS are described in RFC 5487 as to SHA-256/384 and RFC 5489 as to ECDHE_PSK. Josefsson, et al. Expires September 19, 2013 [Page 5] Internet-Draft salsa20tls March 2013 3. Acknowledgements The authors would like to thank D. J. Bernstein, David McGrew, and Wan-Teh Chang for discussion and suggestions. Josefsson, et al. Expires September 19, 2013 [Page 6] Internet-Draft salsa20tls March 2013 4. IANA Considerations IANA is requested to allocate the following numbers in the TLS Cipher Suite Registry: CipherSuite TLS_RSA_WITH_SALSA20R12_SHA1 = {0xTBD, 0xTBD} CipherSuite TLS_RSA_WITH_SALSA20R20_SHA1 = {0xTBD, 0xTBD} CipherSuite TLS_DHE_RSA_WITH_SALSA20R12_SHA1 = {0xTBD, 0xTBD} CipherSuite TLS_DHE_RSA_WITH_SALSA20R20_SHA1 = {0xTBD, 0xTBD} CipherSuite TLS_ECDHE_RSA_WITH_SALSA20R12_SHA1 = {0xTBD, 0xTBD} CipherSuite TLS_ECDHE_RSA_WITH_SALSA20R20_SHA1 = {0xTBD, 0xTBD} CipherSuite TLS_ECDHE_ECDSA_WITH_SALSA20R12_SHA1 = {0xTBD, 0xTBD} CipherSuite TLS_ECDHE_ECDSA_WITH_SALSA20R20_SHA1 = {0xTBD, 0xTBD} CipherSuite TLS_PSK_WITH_SALSA20R12_SHA1 = {0xTBD, 0xTBD} CipherSuite TLS_PSK_WITH_SALSA20R20_SHA1 = {0xTBD, 0xTBD} CipherSuite TLS_DHE_PSK_WITH_SALSA20R12_SHA1 = {0xTBD, 0xTBD} CipherSuite TLS_DHE_PSK_WITH_SALSA20R20_SHA1 = {0xTBD, 0xTBD} CipherSuite TLS_RSA_PSK_WITH_SALSA20R12_SHA1 = {0xTBD, 0xTBD} CipherSuite TLS_RSA_PSK_WITH_SALSA20R20_SHA1 = {0xTBD, 0xTBD} CipherSuite TLS_ECDHE_PSK_WITH_SALSA20R12_SHA1 = {0xTBD, 0xTBD} CipherSuite TLS_ECDHE_PSK_WITH_SALSA20R20_SHA1 = {0xTBD, 0xTBD} Josefsson, et al. Expires September 19, 2013 [Page 7] Internet-Draft salsa20tls March 2013 5. Security Considerations The security of Salsa20 is discussed in the Salsa20 security [SALSA20-SECURITY] paper. The reader must consult cryptographic research to find out the current security status of Salsa20. At the time of writing this document, there are no known significant security problems with Salsa20/12 or Salsa20/20. As of early 2013, the best cryptanalysis breaks 8 out of 20 rounds to recover the 256- bit secret key in 2^251 operations, using 2^31 keystream pairs (see [SALSA20-ATTACK]). For more background, see the eSTREAM report [ESTREAM]. There are no ciphersuites defined in this document that utilize the variant of Salsa20 with 128-bit key material, because (due to the design of Salsa20) they provide no performance advantage over the 256-bit variant. 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. Josefsson, et al. Expires September 19, 2013 [Page 8] Internet-Draft salsa20tls March 2013 6. References 6.1. 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. [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. [SALSA20SPEC] Bernstein, D., "Salsa20 specification", WWW http://cr.yp.to/snuffle/spec.pdf, April 2005. 6.2. Informative References [RFC4418] Krovetz, T., "UMAC: Message Authentication Code using Universal Hashing", RFC 4418, March 2006. [RFC6101] Freier, A., Karlton, P., and P. Kocher, "The Secure Sockets Layer (SSL) Protocol Version 3.0", RFC 6101, August 2011. [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 Josefsson, et al. Expires September 19, 2013 [Page 9] Internet-Draft salsa20tls March 2013 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. [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. Josefsson, et al. Expires September 19, 2013 [Page 10] Internet-Draft salsa20tls March 2013 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/ Nikos Mavrogiannopoulos KU Leuven Email: nikos.mavrogiannopoulos@esat.kuleuven.be Josefsson, et al. Expires September 19, 2013 [Page 11]