--- 1/draft-ietf-ipsecme-chacha20-poly1305-03.txt 2015-04-26 14:14:58.261880604 -0700 +++ 2/draft-ietf-ipsecme-chacha20-poly1305-04.txt 2015-04-26 14:14:58.285881187 -0700 @@ -1,18 +1,18 @@ Network Working Group Y. Nir Internet-Draft Check Point -Intended status: Standards Track April 25, 2015 -Expires: October 27, 2015 +Intended status: Standards Track April 26, 2015 +Expires: October 28, 2015 ChaCha20, Poly1305 and their use in IKE & IPsec - draft-ietf-ipsecme-chacha20-poly1305-03 + draft-ietf-ipsecme-chacha20-poly1305-04 Abstract This document describes the use of the ChaCha20 stream cipher along with the Poly1305 authenticator, combined into an AEAD algorithm for the Internet Key Exchange protocol (IKEv2) and for IPsec. Status of This Memo This Internet-Draft is submitted in full conformance with the @@ -21,52 +21,54 @@ 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 October 27, 2015. + This Internet-Draft will expire on October 28, 2015. Copyright Notice Copyright (c) 2015 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 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 . . . . . . . . . . . . . . . . . . . . . . . . 2 - 1.1. Conventions Used in This Document . . . . . . . . . . . . 2 + 1.1. Conventions Used in This Document . . . . . . . . . . . . 3 2. ChaCha20 & Poly1305 for ESP . . . . . . . . . . . . . . . . . 3 2.1. AAD Construction . . . . . . . . . . . . . . . . . . . . 4 3. Use in IKEv2 . . . . . . . . . . . . . . . . . . . . . . . . 4 - 4. Negotiation in IKEv2 . . . . . . . . . . . . . . . . . . . . 4 + 4. Negotiation in IKEv2 . . . . . . . . . . . . . . . . . . . . 5 5. Security Considerations . . . . . . . . . . . . . . . . . . . 5 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5 7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 5 - 8. References . . . . . . . . . . . . . . . . . . . . . . . . . 5 - 8.1. Normative References . . . . . . . . . . . . . . . . . . 5 + 8. References . . . . . . . . . . . . . . . . . . . . . . . . . 6 + 8.1. Normative References . . . . . . . . . . . . . . . . . . 6 8.2. Informative References . . . . . . . . . . . . . . . . . 6 - Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 6 + Appendix A. ESP Example . . . . . . . . . . . . . . . . . . . . 7 + Appendix B. IKEv2 Example . . . . . . . . . . . . . . . . . . . 9 + Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 11 1. Introduction The Advanced Encryption Standard (AES - [FIPS-197]) has become the gold standard in encryption. Its efficient design, wide implementation, and hardware support allow for high performance in many areas, including IPsec VPNs. On most modern platforms, AES is anywhere from 4x to 10x as fast as the previous most-used cipher, 3-key Data Encryption Standard (3DES - [SP800-67]). 3DES also has a 64-bit block, which means that the amount of data that can be @@ -99,44 +101,46 @@ AEAD_CHACHA20_POLY1305 is a combined mode algorithm, or AEAD. The construction follows the AEAD construction in section 2.8 of [chacha_poly]: o The Initialization Vector (IV) is 64-bit, and is used as part of the nonce. The IV MUST be unique for each invocation for a particular SA but does not need to be unpredictable. The use of a counter or a linear feedback shift register (LFSR) is RECOMMENDED. o A 32-bit Salt is prepended to the 64-bit IV to form the 96-bit nonce. The salt is fixed per SA and it is not transmitted as part - of the ESP packet.. + of the ESP packet. o The encryption key is 256-bit. o The Internet Key Exchange protocol generates a bitstring called KEYMAT using a pseudo-random function (PRF). That KEYMAT is divided into keys for encryption, message authentication and - whatever else is needed. For the ChaCha20-poly1305 algorithm, 256 - bits are used for the key, and a subsequent 32 bits are used for - the Salt. + whatever else is needed. The KEYMAT requested for each + ChaCha20-Poly1305 key is 36 octets. The first 32 octets are the + 256-bit ChaCha20 key, and the remaining four octets are used as + the Salt value in the nonce. The ChaCha20 encryption algorithm requires the following parameters: a 256-bit key, a 96-bit nonce, and a 32-bit initial block counter. For ESP we set these as follows: o The key is set as mentioned above. o The 96-bit nonce is formed from a concatenation of the 32-bit Salt and the 64-bit IV, as described above. o The Initial Block Counter is set to one (1). The reason that one is used for the initial counter rather than zero is that zero is reserved for generating the one-time Poly1305 key (see below) As the ChaCha20 block function is not applied directly to the plaintext, no padding should be necessary. However, in keeping with - the specification in RFC 4303, the ESP does have padding, so as to - align the buffer to an integral multiple of 4 octets. + the specification in RFC 4303, the plaintext always has a pad length + octet and may require padding bytes so as to align the buffer to an + integral multiple of 4 octets. The same key and nonce, along with a block counter of zero are passed to the ChaCha20 block function, and the top 256 bits of the result are used as the Poly1305 key. The nonce passed to the block function here is the same nonce that is used in ChaCha20, including the 32-bit Salt, and the key passed is the same as the encryption key. Finally, the Poly1305 function is run on the data to be authenticated, which is, as specified in section 2.8 of [chacha_poly] a concatenation of the following in the below order: @@ -169,20 +172,23 @@ For SAs with ESN the AAD is 12 bytes: 4-byte SPI followed by an 8-byte sequence number as a 64-bit network order integer. 3. Use in IKEv2 AEAD algorithms can be used in IKE, as described in [RFC5282]. More specifically: o The Encrypted Payload is as described in section 3 of that document. + o The ChaCha20-Poly1305 keying material is derived from KEYMAT as + for ESP: 36 octets are requested, of which the first 32 form the + key and the last 4 form the salt. o The IV is 64 bits, as described in Section 2. o The AAD is as described in section 5.1 of RFC 5282, so it's 32 bytes (28 for the IKEv2 header + 4 bytes for the encrypted payload header) assuming no unencrypted payloads. 4. Negotiation in IKEv2 When negotiating the ChaCha20-Poly1305 algorithm for use in IKE or IPsec, the value xxx (TBA by IANA) should be used in the transform substructure of the SA payload as the ENCR (type 1) transform ID. As @@ -257,34 +263,224 @@ Relations among notions and analysis of the generic composition paradigm", 2000, . [FIPS-197] National Institute of Standards and Technology, "Advanced Encryption Standard (AES)", FIPS PUB 197, November 2001, . + [RFC1761] Callaghan, B. and R. Gilligan, "Snoop Version 2 Packet + Capture File Format", RFC 1761, February 1995, + . + [RFC4106] Viega, J. and D. McGrew, "The Use of Galois/Counter Mode (GCM) in IPsec Encapsulating Security Payload (ESP)", RFC 4106, June 2005. [SP800-67] National Institute of Standards and Technology, "Recommendation for the Triple Data Encryption Algorithm (TDEA) Block Cipher", FIPS SP800-67, January 2012, . [standby-cipher] McGrew, D., Grieco, A., and Y. Sheffer, "Selection of Future Cryptographic Standards", draft-mcgrew-standby- cipher (work in progress), January 2013. +Appendix A. ESP Example + + For this example, we will use a tunnel-mode ESP SA using the + ChaCha20-Poly1305 algorithm. The keying material is as follows: + + KEYMAT: + 000 80 81 82 83 84 85 86 87 88 89 8a 8b 8c 8d 8e 8f ................ + 016 90 91 92 93 94 95 96 97 98 99 9a 9b 9c 9d 9e 9f ................ + 032 a0 a1 a2 a3 .... + + Obviously not a great PRF. The first 32 octets are the key and the + final four octets (0xa0 0xa1 0xa2 0xa3) are the salt. For the + packet, we will use an ICMP packet from 198.51.100.5 to 192.0.2.5: + + Source Packet: + 000 45 00 00 54 a6 f2 00 00 40 01 e7 78 c6 33 64 05 E..T....@..x.3d. + 016 c0 00 02 05 08 00 5b 7a 3a 08 00 00 55 3b ec 10 ......[z:...U;.. + 032 00 07 36 27 08 09 0a 0b 0c 0d 0e 0f 10 11 12 13 ..6'............ + 048 14 15 16 17 18 19 1a 1b 1c 1d 1e 1f 20 21 22 23 ............ !"# + 064 24 25 26 27 28 29 2a 2b 2c 2d 2e 2f 30 31 32 33 $%&'()*+,-./0123 + 080 34 35 36 37 4567 + + The SA details are as follows: + + o The key and Salt are as above. + o The SPI is 0x01 0x02 0x03 0x04. + o The next sequence number is 5; ESN is not enabled. + o The gateway IP address for this side is 203.0.113.153; The peer + address is 203.0.113.5. + o NAT was not detected. + + The 64-bit IV is 0x10 0x11 0x12 0x13 0x14 0x15 0x16 0x17. Putting + together the salt and IV we get the nonce: + + The nonce: + 000 a0 a1 a2 a3 10 11 12 13 14 15 16 17 ............ + + The plaintext to encrypt consists of the source IP packet plus the + padding: + + Plaintext (includes padding and pad length): + 000 45 00 00 54 a6 f2 00 00 40 01 e7 78 c6 33 64 05 E..T....@..x.3d. + 016 c0 00 02 05 08 00 5b 7a 3a 08 00 00 55 3b ec 10 ......[z:...U;.. + 032 00 07 36 27 08 09 0a 0b 0c 0d 0e 0f 10 11 12 13 ..6'............ + 048 14 15 16 17 18 19 1a 1b 1c 1d 1e 1f 20 21 22 23 ............ !"# + 064 24 25 26 27 28 29 2a 2b 2c 2d 2e 2f 30 31 32 33 $%&'()*+,-./0123 + 080 34 35 36 37 01 02 03 03 4567.... + + With the key, nonce and plaintext available, we can call the ChaCha20 + function and encrypt the packet, producing the ciphertext: + + Ciphertext: + 000 24 03 94 28 b9 7f 41 7e 3c 13 75 3a 4f 05 08 7b $..(..A~<.u:O..{ + 016 67 c3 52 e6 a7 fa b1 b9 82 d4 66 ef 40 7a e5 c6 g.R.......f.@z.. + 032 14 ee 80 99 d5 28 44 eb 61 aa 95 df ab 4c 02 f7 .....(D.a....L.. + 048 2a a7 1e 7c 4c 4f 64 c9 be fe 2f ac c6 38 e8 f3 *..|LOd.../..8.. + 064 cb ec 16 3f ac 46 9b 50 27 73 f6 fb 94 e6 64 da ...?.F.P's....d. + 080 91 65 b8 28 29 f6 40 e7 .e.().@. + + To calculate the tag, we need a one-time Poly1305 key, which we + calculate by calling the ChaCha20 function again with the same key + and nonce, but a block count of zero. + + Poly1305 one-time key: + 000 af 1f 41 2c c1 15 ad ce 5e 4d 0e 29 d5 c1 30 bf ..A,....^M.)..0. + 016 46 31 21 0e 0f ef 74 31 c0 45 4f e7 0f d7 c2 d1 F1!...t1.EO..... + + The AAD is constructed by concatenating the SPI to the sequence + number: + + 000 01 02 03 04 00 00 00 05 ........ + + The input to the Poly1305 function is constructed by concatenating + and padding the AAD and ciphertext: + + Poly1305 Input: + 000 01 02 03 04 00 00 00 05 00 00 00 00 00 00 00 00 ................ + 016 24 03 94 28 b9 7f 41 7e 3c 13 75 3a 4f 05 08 7b $..(..A~<.u:O..{ + 032 67 c3 52 e6 a7 fa b1 b9 82 d4 66 ef 40 7a e5 c6 g.R.......f.@z.. + 048 14 ee 80 99 d5 28 44 eb 61 aa 95 df ab 4c 02 f7 .....(D.a....L.. + 064 2a a7 1e 7c 4c 4f 64 c9 be fe 2f ac c6 38 e8 f3 *..|LOd.../..8.. + 080 cb ec 16 3f ac 46 9b 50 27 73 f6 fb 94 e6 64 da ...?.F.P's....d. + 096 91 65 b8 28 29 f6 40 e7 00 00 00 00 00 00 00 00 .e.().@......... + 112 08 00 00 00 00 00 00 00 58 00 00 00 00 00 00 00 ........X....... + + The resulting tag is: + + Tag: + 000 f0 5f ff a1 a0 cc cd de 88 a3 e8 9a 21 2b 18 ba ._..........!+.. + + Putting it all together, the resulting packet is as follows: + + ESP packet: + 000 45 00 00 8c 23 45 00 00 40 32 de 5b cb 00 71 99 E...#E..@2.[..q. + 016 cb 00 71 05 01 02 03 04 00 00 00 05 10 11 12 13 ..q............. + 032 14 15 16 17 24 03 94 28 b9 7f 41 7e 3c 13 75 3a ....$..(..A~<.u: + 048 4f 05 08 7b 67 c3 52 e6 a7 fa b1 b9 82 d4 66 ef O..{g.R.......f. + 064 40 7a e5 c6 14 ee 80 99 d5 28 44 eb 61 aa 95 df @z.......(D.a... + 080 ab 4c 02 f7 2a a7 1e 7c 4c 4f 64 c9 be fe 2f ac .L..*..|LOd.../. + 096 c6 38 e8 f3 cb ec 16 3f ac 46 9b 50 27 73 f6 fb .8.....?.F.P's.. + 112 94 e6 64 da 91 65 b8 28 29 f6 40 e7 f0 5f ff a1 ..d..e.().@.._.. + 128 a0 cc cd de 88 a3 e8 9a 21 2b 18 ba ........!+.. + +Appendix B. IKEv2 Example + + For the IKEv2 example, we'll use the following: + + o The key is 0x80..0x9f, the same as in Appendix A. + o The Salt is 0xa0 0xa1 0xa2 0xa3. + o The IV will also be the same as in the previous example. The fact + that the IV and Salt are both the same means that the nonce is + also the same. + o Because the key and nonce are the same, so is the one-time + Poly1305 key. + o The packet with be an Informational request carrying a single + payload: A Notify payload with type SET_WINDOW_SIZE, setting the + window size to 10. + o iSPI = 0xc0 0xc1 0xc2 0xc3 0xc4 0xc5 0xc6 0xc7. + o rSPI = 0xd0 0xd1 0xd2 0xd3 0xd4 0xd5 0xd6 0xd7. + o Message ID shall be 9. + + The Notify Payload: + 000 00 00 00 0c 00 00 40 01 00 00 00 0a ......@..... + Padding as required by RFC 7296: +
+