\
Network Working Group                                         A. Langley
Internet-Draft                                                  W. Chang
Updates: 5246, 6347                                           Google Inc
(if approved)                                       N. Mavrogiannopoulos
Intended status: Standards Track                                 Red Hat
Expires: July 28, 2014                                   J. Strombergson
                                                      Secworks Sweden AB
                                                            S. Josefsson
                                                                  SJD AB
                                                        January 24, 2014


         The ChaCha Stream Cipher for Transport Layer Security
                 draft-mavrogiannopoulos-chacha-tls-01

Abstract

   This document describes the use of the ChaCha stream cipher with
   HMAC-SHA1 and Poly1305 in 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/.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on July 28, 2014.

Copyright Notice

   Copyright (c) 2014 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect



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   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.


Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
   2.  The ChaCha Cipher  . . . . . . . . . . . . . . . . . . . . . .  4
   3.  The Poly1305 Authenticator . . . . . . . . . . . . . . . . . .  6
   4.  ChaCha20 Cipher Suites . . . . . . . . . . . . . . . . . . . .  7
     4.1.  ChaCha20 Cipher Suites with HMAC-SHA1  . . . . . . . . . .  7
     4.2.  ChaCha20 Cipher Suites with Poly1305 . . . . . . . . . . .  7
   5.  Updates to the TLS Standard Stream Cipher  . . . . . . . . . . 10
   6.  Updates to DTLS  . . . . . . . . . . . . . . . . . . . . . . . 11
   7.  Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 12
   8.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 13
   9.  Security Considerations  . . . . . . . . . . . . . . . . . . . 14
   10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 15
     10.1. Normative References . . . . . . . . . . . . . . . . . . . 15
     10.2. Informative References . . . . . . . . . . . . . . . . . . 15
   Appendix A.  Test vectors  . . . . . . . . . . . . . . . . . . . . 17
     A.1.  ChaCha20 . . . . . . . . . . . . . . . . . . . . . . . . . 17
     A.2.  Poly1305 . . . . . . . . . . . . . . . . . . . . . . . . . 18
     A.3.  AEAD_CHACHA20_POLY1305 . . . . . . . . . . . . . . . . . . 18
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 20
























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1.  Introduction

   This document describes the use of the ChaCha stream cipher 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 [CHACHA] 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
   (AES-GCM) ciphersuites address some of these issues, concerns about
   the performance and ease of software implementation are sometimes
   raised.

   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 and can be
   implemented easily without being vulnerable to software side-channel
   attacks.



















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2.  The ChaCha Cipher

   ChaCha [CHACHA] is a stream cipher developed by D. J. Bernstein in
   2008.  It is a refinement of Salsa20 and was used as the core of the
   SHA-3 finalist, BLAKE.

   The variant of ChaCha used in this document is ChaCha with 20 rounds
   and a 256 bit key, which will be referred to as ChaCha20 in the rest
   of this document.  This is the conservative variant (with respect to
   security) of the ChaCha family.

   ChaCha maps 16, 32-bit input words to 16, 32-bit output words.  By
   convention, 8 of the input words consist of a 256-bit key, 4 are
   constants and the remaining four are a nonce and block counter.  The
   output words are converted to bytes and XORed with the plaintext to
   produce ciphertext.  In order to generate sufficient output bytes to
   XOR with the whole plaintext, the block counter is incremented and
   ChaCha is run again, as many times as needed, for up to 2^70 bytes of
   output.

   ChaCha operates on a state of 16, 32-bit words which are initialised
   from the input words.  The first four input words are constants:

             (0x61707865, 0x3320646e, 0x79622d32, 0x6b206574)

   Input words 4 through 11 are taken from the 256-bit key by reading
   the bytes in little-endian order, in 4-byte chunks.  Input words 12
   and 13 are a block counter, with word 12 overflowing into word 13.
   Lastly, words 14 and 15 are taken from an 8-byte nonce, again by
   reading the bytes in little-endian order, in 4-byte chunks.  The
   block counter words are initially zero.

   ChaCha20 consists of 20 rounds, alternating between "column" rounds
   and "diagonal" rounds.  Each round applies the following "quarter-
   round" function four times, to a different set of words each time.
   The quarter-round function updates 4, 32-bit words (a, b, c, d) as
   follows, where <<< is a bitwise, left rotation:

   a += b; d ^= a; d <<<= 16;
   c += d; b ^= c; b <<<= 12;
   a += b; d ^= a; d <<<= 8;
   c += d; b ^= c; b <<<= 7;

   The 16 words are conceptually arranged in a four by four grid with
   the first word in the top-left position and the fourth word in the
   top-right position.  The "column" rounds then apply the quarter-round
   function to the four columns, from left to right.  The "diagonal"
   rounds apply the quarter-round to the top-left, bottom-right



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   diagonal, followed by the pattern shifted one place to the right, for
   three more quarter-rounds.

   Specifically, a column round applies the quarter-round function to
   the following indexes: (0, 4, 8, 12), (1, 5, 9, 13), (2, 6, 10, 14),
   (3, 7, 11, 15).  A diagonal round applies it to these indexes: (0, 5,
   10, 15), (1, 6, 11, 12), (2, 7, 8, 13), (3, 4, 9, 14).

   After 20 rounds of the above processing, the original 16 input words
   are added to the 16 words to form the 16 output words.

   The 64 output bytes are generated from the 16 output words by
   serializing them in little-endian order and concatenating the
   results.

   Test vectors for this cipher can be found in Appendix A.1.



































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3.  The Poly1305 Authenticator

   Poly1305 [POLY1305] is a Wegman-Carter, one-time authenticator
   designed by D. J. Bernstein.  Poly1305 takes a 32-byte, one-time key
   and a message and produces a 16-byte tag that authenticates the
   message such that an attacker has a negligible chance of producing a
   valid tag for an inauthentic message.

   The first 16 bytes of the one-time key form an integer, _r_, as
   follows: the top four bits of the bytes at indexes 3, 7, 11 and 15
   are cleared, the bottom 2 bits of the bytes at indexes 4, 8 and 12
   are cleared and the 16 bytes are taken as a little-endian value.

   An accumulator is set to zero.  For each chunk of 16 bytes from the
   input message, a byte with value 1 is appended and the 17 bytes are
   treated as a little-endian number.  If the last chunk has less than
   16 bytes then zero bytes are appended after the 1 byte is appended
   until there are 17 bytes.  The value is added to the accumulator and
   then the accumulator is multiplied by _r_, all mod 2^130 - 5.

   Finally the last 16 bytes of the one-time key are treated as a
   little-endian number and added to the accumulator, mod 2^128.  The
   result is serialised as a little-endian number, producing the 16 byte
   tag.  Note that the original specification of Poly1305 used a
   different construction with AES to generate the constant term of the
   polynomial from a counter nonce.  For a more recent treatment that
   avoids the use of a block cipher in this fashion, as is done here,
   see section 9 of the NaCl specification [NACLCRYPTO].

   Test vectors for this authenticator can be found in Appendix A.2.





















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4.  ChaCha20 Cipher Suites

   In the next sections different ciphersuites are defined that utilize
   the ChaCha20 cipher combined with various message authentication
   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.

   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].

4.1.  ChaCha20 Cipher Suites with HMAC-SHA1

   The following CipherSuites are defined.

    TLS_RSA_WITH_CHACHA20_SHA              = {0xTBD, 0xTBD} {0xCC, 0x20}
    TLS_ECDHE_RSA_WITH_CHACHA20_SHA        = {0xTBD, 0xTBD} {0xCC, 0x21}
    TLS_ECDHE_ECDSA_WITH_CHACHA20_SHA      = {0xTBD, 0xTBD} {0xCC, 0x22}

    TLS_DHE_RSA_WITH_CHACHA20_SHA          = {0xTBD, 0xTBD} {0xCC, 0x23}
    TLS_DHE_PSK_WITH_CHACHA20_SHA          = {0xTBD, 0xTBD} {0xCC, 0x24}

    TLS_PSK_WITH_CHACHA20_SHA              = {0xTBD, 0xTBD} {0xCC, 0x25}
    TLS_ECDHE_PSK_WITH_CHACHA20_SHA        = {0xTBD, 0xTBD} {0xCC, 0x26}
    TLS_RSA_PSK_WITH_CHACHA20_SHA          = {0xTBD, 0xTBD} {0xCC, 0x27}

   Note that ChaCha20 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 MAC algorithm used in the ciphersuites above is HMAC-SHA1
   [RFC6234].

4.2.  ChaCha20 Cipher Suites with Poly1305

   The ChaCha20 and Poly1305 primitives are built into an AEAD algorithm
   [RFC5116], AEAD_CHACHA20_POLY1305, that takes a 32 byte key and 8
   byte nonce as follows.

   ChaCha20 is run with the given key and nonce and with the two counter
   words set to zero.  The first 32 bytes of the 64 byte output are
   saved to become the one-time key for Poly1305.  The remainder of the



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   output is discarded.  The first counter input word is set to one and
   the plaintext is encrypted by XORing it with the output of
   invocations of the ChaCha20 function as needed, incrementing the
   first counter word after each block and overflowing into the second.
   The limits on the TLS plaintext size mean that the first counter word
   will never overflow in practice.

   The reason for generating the Poly1305 key like this rather than
   using key material from the handshake is that handshake key material
   is per-session, but for a polynomial MAC, a unique, secret key is
   needed per-record.

   The Poly1305 key is used to calculate a tag for the following input:
   the concatenation of the additional data, the number of bytes of
   additional data, the ciphertext and the number of bytes of
   ciphertext.  Numbers are represented as 8-byte, little-endian values.
   The resulting tag is appended to the ciphertext, resulting in the
   output of the AEAD operation.

   Authenticated decryption is largely the reverse of the encryption
   process: generate one block of ChaCha20 keystream and use the first
   32 bytes as a Poly1305 key.  Feed Poly1305 the additional data and
   ciphertext, with the length suffixing as described above.  Verify, in
   constant time, that the calculated Poly1305 authenticator matches the
   final 16 bytes of the input.  If not, the input can be rejected
   immediately.  Otherwise, run ChaCha20, starting with a counter value
   of one, to decrypt the ciphertext.

   When used in TLS, the "record_iv_length" is zero and the nonce is the
   sequence number for the record, as an 8-byte, big-endian number.  The
   additional data is seq_num + TLSCompressed.type +
   TLSCompressed.version + TLSCompressed.length, where "+" denotes
   concatenation.

   In DTLS, the nonce is formed as the concatenation of the 16-bit epoch
   with the 48-bit sequence number.

   In accordance with section 4 of RFC 5116 [RFC5116], the constants for
   this AEAD algorithm are as follows: K_LEN is 32 bytes, N_MIN and
   N_MAX are 8 bytes, P_MAX and A_MAX are 2^64, C_MAX is 2^64+16.  An
   AEAD_CHACHA20_POLY1305 ciphertext is exactly 16 octets longer than
   its corresponding plaintext.

   Test vectors for this authenticator can be found in Appendix A.3.

   The following CipherSuites are defined.





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    TLS_RSA_WITH_CHACHA20_POLY1305         = {0xTBD, 0xTBD} {0xCC, 0x12}
    TLS_ECDHE_RSA_WITH_CHACHA20_POLY1305   = {0xTBD, 0xTBD} {0xCC, 0x13}
    TLS_ECDHE_ECDSA_WITH_CHACHA20_POLY1305 = {0xTBD, 0xTBD} {0xCC, 0x14}

    TLS_DHE_RSA_WITH_CHACHA20_POLY1305     = {0xTBD, 0xTBD} {0xCC, 0x15}
    TLS_DHE_PSK_WITH_CHACHA20_POLY1305     = {0xTBD, 0xTBD} {0xCC, 0x16}

    TLS_PSK_WITH_CHACHA20_POLY1305         = {0xTBD, 0xTBD} {0xCC, 0x17}
    TLS_ECDHE_PSK_WITH_CHACHA20_POLY1305   = {0xTBD, 0xTBD} {0xCC, 0x18}
    TLS_RSA_PSK_WITH_CHACHA20_POLY1305     = {0xTBD, 0xTBD} {0xCC, 0x19}









































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5.  Updates to the TLS Standard Stream Cipher

   The ChaCha20 ciphersuites with HMAC-SHA1 defined in this document
   differ from the TLS RC4 ciphersuites that have been the basis for the
   definition of Standard Stream Cipher.  Unlike RC4, ChaCha20 requires
   a nonce per record.  This however, does not affect the description of
   the Standard Stream Cipher if one assumes that a nonce is optional
   and depends on the cipher's characteristics.

   Hence, this document modifies the Standard Stream Cipher by adding an
   implicit nonce of 8-bytes, which is set to be the 64-bit TLS record
   sequence number.  If the stream cipher needs more than 8 byte of
   nonce, it can obtain additional bytes for the implicit nonce from the
   client_write_iv and server_write_iv of the key_block.

   Stream ciphers that don't require a nonce such as RC4 shall ignore
   it.  Other stream ciphers that require a nonce, such as ChaCha20 with
   HMAC-SHA1, will use the nonce and reset their state on each record.

   Note that in case of DTLS the 8-byte nonce is formed as the
   concatenation of the 16-bit epoch with the 48-bit sequence number,
   which are sent as part of the record.





























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6.  Updates to DTLS

   The DTLS protocol requires the cipher in use to introduce no
   dependencies between TLS Records to allow lost or rearranged records.
   For that it explicitly bans stream ciphers (see Section 3.1 of
   [RFC6347]).

   As the stream cipher described in this document, unlike RC4, does not
   require dependencies between records, this ban of stream ciphers is
   lifted with this document.  Stream ciphers can be used with DTLS if
   they introduce no dependencies between records.








































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7.  Acknowledgements

   The authors would like to thank Zooko Wilcox-OHearn and Samuel Neves.
















































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8.  IANA Considerations

   IANA is requested to assign a value for AEAD_CHACHA20_POLY1305 in the
   registry of AEAD algorithms [RFC5116], and also allocate the
   following Cipher Suites in the TLS Cipher Suite Registry (note that
   the third column contains the suggested ciphersuite numbers):

    TLS_RSA_WITH_CHACHA20_POLY1305         = {0xTBD, 0xTBD} {0xCC, 0x12}
    TLS_ECDHE_RSA_WITH_CHACHA20_POLY1305   = {0xTBD, 0xTBD} {0xCC, 0x13}
    TLS_ECDHE_ECDSA_WITH_CHACHA20_POLY1305 = {0xTBD, 0xTBD} {0xCC, 0x14}

    TLS_DHE_RSA_WITH_CHACHA20_POLY1305     = {0xTBD, 0xTBD} {0xCC, 0x15}
    TLS_DHE_PSK_WITH_CHACHA20_POLY1305     = {0xTBD, 0xTBD} {0xCC, 0x16}

    TLS_PSK_WITH_CHACHA20_POLY1305         = {0xTBD, 0xTBD} {0xCC, 0x17}
    TLS_ECDHE_PSK_WITH_CHACHA20_POLY1305   = {0xTBD, 0xTBD} {0xCC, 0x18}
    TLS_RSA_PSK_WITH_CHACHA20_POLY1305     = {0xTBD, 0xTBD} {0xCC, 0x19}

    TLS_RSA_WITH_CHACHA20_SHA              = {0xTBD, 0xTBD} {0xCC, 0x20}
    TLS_ECDHE_RSA_WITH_CHACHA20_SHA        = {0xTBD, 0xTBD} {0xCC, 0x21}
    TLS_ECDHE_ECDSA_WITH_CHACHA20_SHA      = {0xTBD, 0xTBD} {0xCC, 0x22}

    TLS_DHE_RSA_WITH_CHACHA20_SHA          = {0xTBD, 0xTBD} {0xCC, 0x23}
    TLS_DHE_PSK_WITH_CHACHA20_SHA          = {0xTBD, 0xTBD} {0xCC, 0x24}

    TLS_PSK_WITH_CHACHA20_SHA              = {0xTBD, 0xTBD} {0xCC, 0x25}
    TLS_ECDHE_PSK_WITH_CHACHA20_SHA        = {0xTBD, 0xTBD} {0xCC, 0x26}
    TLS_RSA_PSK_WITH_CHACHA20_SHA          = {0xTBD, 0xTBD} {0xCC, 0x27}























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9.  Security Considerations

   ChaCha20 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 ChaCha20 is shown to be more
   resistant in certain attacks than Salsa20 [SALSA20-ATTACK].
   Furthermore ChaCha20 was used as the core of the BLAKE hash function,
   a SHA3 finalist, that had received considerable cryptanalytic
   attention [NIST-SHA3].

   Poly1305 is designed to ensure that forged messages are rejected with
   a probability of 1-(n/2^102) for a 16*n byte message, even after
   sending 2^64 legitimate messages.

   The cipher suites described in this document require that an nonce is
   never repeated under the same key.  The design presented ensures that
   by using the TLS sequence number which is unique and does not wrap
   [RFC5246].

   This document should not introduce any other security considerations
   than those that directly follow from the use of the stream cipher
   ChaCha20, the AEAD_CHACHA20_POLY1305 construction, and those that
   directly follow from introducing any set of stream cipher suites into
   TLS and DTLS.


























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10.  References

10.1.  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.

   [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.

   [RFC5116]  McGrew, D., "An Interface and Algorithms for Authenticated
              Encryption", RFC 5116, January 2008.

   [RFC5246]  Dierks, T. and E. Rescorla, "The Transport Layer Security
              (TLS) Protocol Version 1.2", RFC 5246, August 2008.

   [RFC5489]  Badra, M. and I. Hajjeh, "ECDHE_PSK Cipher Suites for
              Transport Layer Security (TLS)", RFC 5489, March 2009.

   [RFC6234]  Eastlake, D. and T. Hansen, "US Secure Hash Algorithms
              (SHA and SHA-based HMAC and HKDF)", RFC 6234, May 2011.

   [RFC6347]  Rescorla, E. and N. Modadugu, "Datagram Transport Layer
              Security Version 1.2", RFC 6347, January 2012.

   [CHACHA]   Bernstein, D., "ChaCha, a variant of Salsa20",
              January 2008,
              <http://cr.yp.to/chacha/chacha-20080128.pdf>.

   [POLY1305]
              Bernstein, D., "The Poly1305-AES message-authentication
              code.", March 2005,
              <http://cr.yp.to/mac/poly1305-20050329.pdf>.

10.2.  Informative References

   [SALSA20SPEC]
              Bernstein, D., "Salsa20 specification", April 2005,
              <http://cr.yp.to/snuffle/spec.pdf>.

   [RFC6101]  Freier, A., Karlton, P., and P. Kocher, "The Secure



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              Sockets Layer (SSL) Protocol Version 3.0", RFC 6101,
              August 2011.

   [SALSA20-SECURITY]
              Bernstein, D., "Salsa20 security", April 2005,
              <http://cr.yp.to/snuffle/security.pdf>.

   [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)", September 2008,
              <http://www.ecrypt.eu.org/stream/finallist.html>.

   [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.

   [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", 2007,
              <http://eprint.iacr.org/2007/472.pdf>.

   [NACLCRYPTO]
              Bernstein, D., "Cryptography in NaCl", March 2009,
              <http://cr.yp.to/highspeed/naclcrypto-20090310.pdf>.

   [NIST-SHA3]
              Chang, S., Burr, W., Kelsey, J., Paul, S., and L. Bassham,
              "Third-Round Report of the SHA-3 Cryptographic Hash
              Algorithm Competition", 2012,
              <http://dx.doi.org/10.6028/NIST.IR.7896>.













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Appendix A.  Test vectors

A.1.  ChaCha20

   The following blocks contain test vectors for ChaCha20.  The first
   line contains the 256-bit key, the second the 64-bit nonce and the
   last line contains a prefix of the resulting ChaCha20 key-stream.

   KEY:       00000000000000000000000000000000000000000000000000000000
              00000000
   NONCE:     0000000000000000
   KEYSTREAM: 76b8e0ada0f13d90405d6ae55386bd28bdd219b8a08ded1aa836efcc
              8b770dc7da41597c5157488d7724e03fb8d84a376a43b8f41518a11c
              c387b669b2ee6586


   KEY:       00000000000000000000000000000000000000000000000000000000
              00000001
   NONCE:     0000000000000000
   KEYSTREAM: 4540f05a9f1fb296d7736e7b208e3c96eb4fe1834688d2604f450952
              ed432d41bbe2a0b6ea7566d2a5d1e7e20d42af2c53d792b1c43fea81
              7e9ad275ae546963


   KEY:       00000000000000000000000000000000000000000000000000000000
              00000000
   NONCE:     0000000000000001
   KEYSTREAM: de9cba7bf3d69ef5e786dc63973f653a0b49e015adbff7134fcb7df1
              37821031e85a050278a7084527214f73efc7fa5b5277062eb7a0433e
              445f41e3


   KEY:       00000000000000000000000000000000000000000000000000000000
              00000000
   NONCE:     0100000000000000
   KEYSTREAM: ef3fdfd6c61578fbf5cf35bd3dd33b8009631634d21e42ac33960bd1
              38e50d32111e4caf237ee53ca8ad6426194a88545ddc497a0b466e7d
              6bbdb0041b2f586b













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   KEY:       000102030405060708090a0b0c0d0e0f101112131415161718191a1b
              1c1d1e1f
   NONCE:     0001020304050607
   KEYSTREAM: f798a189f195e66982105ffb640bb7757f579da31602fc93ec01ac56
              f85ac3c134a4547b733b46413042c9440049176905d3be59ea1c53f1
              5916155c2be8241a38008b9a26bc35941e2444177c8ade6689de9526
              4986d95889fb60e84629c9bd9a5acb1cc118be563eb9b3a4a472f82e
              09a7e778492b562ef7130e88dfe031c79db9d4f7c7a899151b9a4750
              32b63fc385245fe054e3dd5a97a5f576fe064025d3ce042c566ab2c5
              07b138db853e3d6959660996546cc9c4a6eafdc777c040d70eaf46f7
              6dad3979e5c5360c3317166a1c894c94a371876a94df7628fe4eaaf2
              ccb27d5aaae0ad7ad0f9d4b6ad3b54098746d4524d38407a6deb3ab7
              8fab78c9

A.2.  Poly1305

   The following blocks contain test vectors for Poly1305.  The first
   line contains a variable length input.  The second contains the 256-
   bit key and the last contains the resulting, 128-bit tag.

   INPUT: 000000000000000000000000000000000000000000000000000000000000
          0000
   KEY:   746869732069732033322d62797465206b657920666f7220506f6c793133
          3035
   TAG:   49ec78090e481ec6c26b33b91ccc0307


   INPUT: 48656c6c6f20776f726c6421
   KEY:   746869732069732033322d62797465206b657920666f7220506f6c793133
          3035
   TAG:   a6f745008f81c916a20dcc74eef2b2f0

A.3.  AEAD_CHACHA20_POLY1305

   The following block contains a test vector for the
   AEAD_CHACHA20_POLY1305 algorithm.  The first four lines consist of
   the standard inputs to an AEAD algorithm and the last line contains
   the encrypted and authenticated result.

   KEY:    4290bcb154173531f314af57f3be3b5006da371ece272afa1b5dbdd110
           0a1007
   INPUT:  86d09974840bded2a5ca
   NONCE:  cd7cf67be39c794a
   AD:     87e229d4500845a079c0
   OUTPUT: e3e446f7ede9a19b62a4677dabf4e3d24b876bb284753896e1d6

   To aid implementations, the next block contains some intermediate
   values in the AEAD_CHACHA20_POLY1305 algorithm.  The first line



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   contains the Poly1305 key that is derived and the second contains the
   raw bytes that are authenticated by Poly1305.

   KEY:   9052a6335505b6d507341169783dccac0e26f84ea84906b1558c05bf4815
          0fbe
   INPUT: 87e229d4500845a079c00a00000000000000e3e446f7ede9a19b62a40a00
          000000000000












































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Authors' Addresses

   Adam Langley
   Google Inc

   Email: agl@google.com


   Wan-Teh Chang
   Google Inc

   Email: wtc@google.com


   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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