idnits 2.17.1 draft-nir-cfrg-chacha20-poly1305-04.txt: Checking boilerplate required by RFC 5378 and the IETF Trust (see https://trustee.ietf.org/license-info): ---------------------------------------------------------------------------- No issues found here. Checking nits according to https://www.ietf.org/id-info/1id-guidelines.txt: ---------------------------------------------------------------------------- No issues found here. Checking nits according to https://www.ietf.org/id-info/checklist : ---------------------------------------------------------------------------- No issues found here. Miscellaneous warnings: ---------------------------------------------------------------------------- == The copyright year in the IETF Trust and authors Copyright Line does not match the current year == Line 225 has weird spacing: '...db886dc c9a62...' == Line 275 has weird spacing: '...ccccccc ccccc...' == Line 276 has weird spacing: '...kkkkkkk kkkkk...' == Line 277 has weird spacing: '...kkkkkkk kkkkk...' == Line 278 has weird spacing: '...bbbbbbb nnnnn...' == (9 more instances...) == The document seems to use 'NOT RECOMMENDED' as an RFC 2119 keyword, but does not include the phrase in its RFC 2119 key words list. -- The document date (May 21, 2014) is 3627 days in the past. Is this intentional? -- Found something which looks like a code comment -- if you have code sections in the document, please surround them with '' and '' lines. Checking references for intended status: Informational ---------------------------------------------------------------------------- -- Looks like a reference, but probably isn't: '3' on line 498 -- Looks like a reference, but probably isn't: '7' on line 499 -- Looks like a reference, but probably isn't: '11' on line 500 -- Looks like a reference, but probably isn't: '15' on line 501 -- Looks like a reference, but probably isn't: '4' on line 502 -- Looks like a reference, but probably isn't: '8' on line 503 -- Looks like a reference, but probably isn't: '12' on line 504 -- Looks like a reference, but probably isn't: '16' on line 496 -- Obsolete informational reference (is this intentional?): RFC 5996 (Obsoleted by RFC 7296) Summary: 0 errors (**), 0 flaws (~~), 8 warnings (==), 11 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Network Working Group Y. Nir 3 Internet-Draft Check Point 4 Intended status: Informational A. Langley 5 Expires: November 22, 2014 Google Inc 6 May 21, 2014 8 ChaCha20 and Poly1305 for IETF protocols 9 draft-nir-cfrg-chacha20-poly1305-04 11 Abstract 13 This document defines the ChaCha20 stream cipher, as well as the use 14 of the Poly1305 authenticator, both as stand-alone algorithms, and as 15 a "combined mode", or Authenticated Encryption with Additional Data 16 (AEAD) algorithm. 18 This document does not introduce any new crypto, but is meant to 19 serve as a stable reference and an implementation guide. 21 Status of this Memo 23 This Internet-Draft is submitted in full conformance with the 24 provisions of BCP 78 and BCP 79. 26 Internet-Drafts are working documents of the Internet Engineering 27 Task Force (IETF). Note that other groups may also distribute 28 working documents as Internet-Drafts. The list of current Internet- 29 Drafts is at http://datatracker.ietf.org/drafts/current/. 31 Internet-Drafts are draft documents valid for a maximum of six months 32 and may be updated, replaced, or obsoleted by other documents at any 33 time. It is inappropriate to use Internet-Drafts as reference 34 material or to cite them other than as "work in progress." 36 This Internet-Draft will expire on November 22, 2014. 38 Copyright Notice 40 Copyright (c) 2014 IETF Trust and the persons identified as the 41 document authors. All rights reserved. 43 This document is subject to BCP 78 and the IETF Trust's Legal 44 Provisions Relating to IETF Documents 45 (http://trustee.ietf.org/license-info) in effect on the date of 46 publication of this document. Please review these documents 47 carefully, as they describe your rights and restrictions with respect 48 to this document. 50 Table of Contents 52 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 53 1.1. Conventions Used in This Document . . . . . . . . . . . . 3 54 2. The Algorithms . . . . . . . . . . . . . . . . . . . . . . . . 4 55 2.1. The ChaCha Quarter Round . . . . . . . . . . . . . . . . . 4 56 2.1.1. Test Vector for the ChaCha Quarter Round . . . . . . . 4 57 2.2. A Quarter Round on the ChaCha State . . . . . . . . . . . 5 58 2.2.1. Test Vector for the Quarter Round on the ChaCha 59 state . . . . . . . . . . . . . . . . . . . . . . . . 5 60 2.3. The ChaCha20 block Function . . . . . . . . . . . . . . . 6 61 2.3.1. Test Vector for the ChaCha20 Block Function . . . . . 7 62 2.4. The ChaCha20 encryption algorithm . . . . . . . . . . . . 8 63 2.4.1. Example and Test Vector for the ChaCha20 Cipher . . . 9 64 2.5. The Poly1305 algorithm . . . . . . . . . . . . . . . . . . 11 65 2.5.1. Poly1305 Example and Test Vector . . . . . . . . . . . 12 66 2.6. Generating the Poly1305 key using ChaCha20 . . . . . . . . 14 67 2.6.1. Poly1305 Key Generation Test Vector . . . . . . . . . 14 68 2.7. A Pseudo-Random Function for ChaCha/Poly-1305 based 69 Crypto Suites . . . . . . . . . . . . . . . . . . . . . . 15 70 2.8. AEAD Construction . . . . . . . . . . . . . . . . . . . . 16 71 2.8.1. Example and Test Vector for AEAD_CHACHA20-POLY1305 . . 17 72 3. Implementation Advice . . . . . . . . . . . . . . . . . . . . 19 73 4. Security Considerations . . . . . . . . . . . . . . . . . . . 20 74 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 21 75 6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 21 76 7. References . . . . . . . . . . . . . . . . . . . . . . . . . . 21 77 7.1. Normative References . . . . . . . . . . . . . . . . . . . 21 78 7.2. Informative References . . . . . . . . . . . . . . . . . . 21 79 Appendix A. Additional Test Vectors . . . . . . . . . . . . . . . 22 80 A.1. The ChaCha20 Block Functions . . . . . . . . . . . . . . . 22 81 A.2. ChaCha20 Encryption . . . . . . . . . . . . . . . . . . . 25 82 A.3. Poly1305 Message Authentication Code . . . . . . . . . . . 28 83 A.4. Poly1305 Key Generation Using ChaCha20 . . . . . . . . . . 32 84 A.5. ChaCha20-Poly1305 AEAD Decryption . . . . . . . . . . . . 33 85 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 36 87 1. Introduction 89 The Advanced Encryption Standard (AES - [FIPS-197]) has become the 90 gold standard in encryption. Its efficient design, wide 91 implementation, and hardware support allow for high performance in 92 many areas. On most modern platforms, AES is anywhere from 4x to 10x 93 as fast as the previous most-used cipher, 3-key Data Encryption 94 Standard (3DES - [FIPS-46]), which makes it not only the best choice, 95 but the only practical choice. 97 The problem is that if future advances in cryptanalysis reveal a 98 weakness in AES, users will be in an unenviable position. With the 99 only other widely supported cipher being the much slower 3DES, it is 100 not feasible to re-configure implementations to use 3DES. 101 [standby-cipher] describes this issue and the need for a standby 102 cipher in greater detail. 104 This document defines such a standby cipher. We use ChaCha20 105 ([chacha]) with or without the Poly1305 ([poly1305]) authenticator. 106 These algorithms are not just fast and secure. They are fast even in 107 software-only C-language implementations, allowing for much quicker 108 deployment when compared with algorithms such as AES that are 109 significantly accelerated by hardware implementations. 111 These document does not introduce these new algorithms. They have 112 been defined in scientific papers by D. J. Bernstein, which are 113 referenced by this document. The purpose of this document is to 114 serve as a stable reference for IETF documents making use of these 115 algorithms. 117 1.1. Conventions Used in This Document 119 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 120 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 121 document are to be interpreted as described in [RFC2119]. 123 The description of the ChaCha algorithm will at various time refer to 124 the ChaCha state as a "vector" or as a "matrix". This follows the 125 use of these terms in DJB's paper. The matrix notation is more 126 visually convenient, and gives a better notion as to why some rounds 127 are called "column rounds" while others are called "diagonal rounds". 128 Here's a diagram of how to martices relate to vectors (using the C 129 language convention of zero being the index origin). 131 0 1 2 3 132 4 5 6 7 133 8 9 10 11 134 12 13 14 15 136 The elements in this vector or matrix are 32-bit unsigned integers. 138 The algorithm name is "ChaCha". "ChaCha20" is a specific instance 139 where 20 "rounds" (or 80 quarter rounds - see Section 2.1) are used. 140 Other variations are defined, with 8 or 12 rounds, but in this 141 document we only describe the 20-round ChaCha, so the names "ChaCha" 142 and "ChaCha20" will be used interchangeably. 144 2. The Algorithms 146 The subsections below describe the algorithms used and the AEAD 147 construction. 149 2.1. The ChaCha Quarter Round 151 The basic operation of the ChaCha algorithm is the quarter round. It 152 operates on four 32-bit unsigned integers, denoted a, b, c, and d. 153 The operation is as follows (in C-like notation): 154 o a += b; d ^= a; d <<<= 16; 155 o c += d; b ^= c; b <<<= 12; 156 o a += b; d ^= a; d <<<= 8; 157 o c += d; b ^= c; b <<<= 7; 158 Where "+" denotes integer addition without carry, "^" denotes a 159 bitwise XOR, and "<<< n" denotes an n-bit left rotation (towards the 160 high bits). 162 For example, let's see the add, XOR and roll operations from the 163 first line with sample numbers: 164 o b = 0x01020304 165 o a = 0x11111111 166 o d = 0x01234567 167 o a = a + b = 0x11111111 + 0x01020304 = 0x12131415 168 o d = d ^ a = 0x01234567 ^ 0x12131415 = 0x13305172 169 o d = d<<<16 = 0x51721330 171 2.1.1. Test Vector for the ChaCha Quarter Round 173 For a test vector, we will use the same numbers as in the example, 174 adding something random for c. 175 o a = 0x11111111 176 o b = 0x01020304 177 o c = 0x9b8d6f43 178 o d = 0x01234567 180 After running a Quarter Round on these 4 numbers, we get these: 182 o a = 0xea2a92f4 183 o b = 0xcb1cf8ce 184 o c = 0x4581472e 185 o d = 0x5881c4bb 187 2.2. A Quarter Round on the ChaCha State 189 The ChaCha state does not have 4 integer numbers, but 16. So the 190 quarter round operation works on only 4 of them - hence the name. 191 Each quarter round operates on 4 pre-determined numbers in the ChaCha 192 state. We will denote by QUATERROUND(x,y,z,w) a quarter-round 193 operation on the numbers at indexes x, y, z, and w of the ChaCha 194 state when viewed as a vector. For example, if we apply 195 QUARTERROUND(1,5,9,13) to a state, this means running the quarter 196 round operation on the elements marked with an asterisk, while 197 leaving the others alone: 199 0 *a 2 3 200 4 *b 6 7 201 8 *c 10 11 202 12 *d 14 15 204 Note that this run of quarter round is part of what is called a 205 "column round". 207 2.2.1. Test Vector for the Quarter Round on the ChaCha state 209 For a test vector, we will use a ChaCha state that was generated 210 randomly: 212 Sample ChaCha State 214 879531e0 c5ecf37d 516461b1 c9a62f8a 215 44c20ef3 3390af7f d9fc690b 2a5f714c 216 53372767 b00a5631 974c541a 359e9963 217 5c971061 3d631689 2098d9d6 91dbd320 219 We will apply the QUARTERROUND(2,7,8,13) operation to this state. 220 For obvious reasons, this one is part of what is called a "diagonal 221 round": 223 After applying QUARTERROUND(2,7,8,13) 225 879531e0 c5ecf37d bdb886dc c9a62f8a 226 44c20ef3 3390af7f d9fc690b cfacafd2 227 e46bea80 b00a5631 974c541a 359e9963 228 5c971061 ccc07c79 2098d9d6 91dbd320 230 Note that only the numbers in positions 2, 7, 8, and 13 changed. 232 2.3. The ChaCha20 block Function 234 The ChaCha block function transforms a ChaCha state by running 235 multiple quarter rounds. 237 The inputs to ChaCha20 are: 238 o A 256-bit key, treated as a concatenation of 8 32-bit little- 239 endian integers. 240 o A 96-bit nonce, treated as a concatenation of 3 32-bit little- 241 endian integers. 242 o A 32-bit block count parameter, treated as a 32-bit little-endian 243 integer. 245 The output is 64 random-looking bytes. 247 The ChaCha algorithm described here uses a 256-bit key. The original 248 algorithm also specified 128-bit keys and 8- and 12-round variants, 249 but these are out of scope for this document. In this section we 250 describe the ChaCha block function. 252 Note also that the original ChaCha had a 64-bit nonce and 64-bit 253 block count. We have modified this here to be more consistent with 254 recommendations in section 3.2 of [RFC5116]. This limits the use of 255 a single (key,nonce) combination to 2^32 blocks, or 256 GB, but that 256 is enough for most uses. In cases where a single key is used by 257 multiple senders, it is important to make sure that they don't use 258 the same nonces. This can be assured by partitioning the nonce space 259 so that the first 32 bits are unique per sender, while the other 64 260 bits come from a counter. 262 The ChaCha20 state is initialized as follows: 263 o The first 4 words (0-3) are constants: 0x61707865, 0x3320646e, 264 0x79622d32, 0x6b206574. 265 o The next 8 words (4-11) are taken from the 256-bit key by reading 266 the bytes in little-endian order, in 4-byte chunks. 267 o Word 12 is a block counter. Since each block is 64-byte, a 32-bit 268 word is enough for 256 Gigabytes of data. 270 o Words 13-15 are a nonce, which should not be repeated for the same 271 key. The 13th word is the first 32 bits of the input nonce taken 272 as a little-endian integer, while the 15th word is the last 32 273 bits. 275 cccccccc cccccccc cccccccc cccccccc 276 kkkkkkkk kkkkkkkk kkkkkkkk kkkkkkkk 277 kkkkkkkk kkkkkkkk kkkkkkkk kkkkkkkk 278 bbbbbbbb nnnnnnnn nnnnnnnn nnnnnnnn 280 c=constant k=key b=blockcount n=nonce 282 ChaCha20 runs 20 rounds, alternating between "column" and "diagonal" 283 rounds. Each round is 4 quarter-rounds, and they are run as follows. 284 Quarter-rounds 1-4 are part of a "column" round, while 5-8 are part 285 of a "diagonal" round: 286 1. QUARTERROUND ( 0, 4, 8,12) 287 2. QUARTERROUND ( 1, 5, 9,13) 288 3. QUARTERROUND ( 2, 6,10,14) 289 4. QUARTERROUND ( 3, 7,11,15) 290 5. QUARTERROUND ( 0, 5,10,15) 291 6. QUARTERROUND ( 1, 6,11,12) 292 7. QUARTERROUND ( 2, 7, 8,13) 293 8. QUARTERROUND ( 3, 4, 9,14) 295 At the end of 20 rounds, the original input words are added to the 296 output words, and the result is serialized by sequencing the words 297 one-by-one in little-endian order. 299 2.3.1. Test Vector for the ChaCha20 Block Function 301 For a test vector, we will use the following inputs to the ChaCha20 302 block function: 303 o Key = 00:01:02:03:04:05:06:07:08:09:0a:0b:0c:0d:0e:0f:10:11:12:13: 304 14:15:16:17:18:19:1a:1b:1c:1d:1e:1f. The key is a sequence of 305 octets with no particular structure before we copy it into the 306 ChaCha state. 307 o Nonce = (00:00:00:09:00:00:00:4a:00:00:00:00) 308 o Block Count = 1. 310 After setting up the ChaCha state, it looks like this: 312 ChaCha State with the key set up. 314 61707865 3320646e 79622d32 6b206574 315 03020100 07060504 0b0a0908 0f0e0d0c 316 13121110 17161514 1b1a1918 1f1e1d1c 317 00000001 09000000 4a000000 00000000 319 After running 20 rounds (10 column rounds interleaved with 10 320 diagonal rounds), the ChaCha state looks like this: 322 ChaCha State after 20 rounds 324 837778ab e238d763 a67ae21e 5950bb2f 325 c4f2d0c7 fc62bb2f 8fa018fc 3f5ec7b7 326 335271c2 f29489f3 eabda8fc 82e46ebd 327 d19c12b4 b04e16de 9e83d0cb 4e3c50a2 329 Finally we add the original state to the result (simple vector or 330 matrix addition), giving this: 332 ChaCha State at the end of the ChaCha20 operation 334 e4e7f110 15593bd1 1fdd0f50 c47120a3 335 c7f4d1c7 0368c033 9aaa2204 4e6cd4c3 336 466482d2 09aa9f07 05d7c214 a2028bd9 337 d19c12b5 b94e16de e883d0cb 4e3c50a2 339 After we serialize the state, we get this: 341 Serialized Block: 342 000 10 f1 e7 e4 d1 3b 59 15 50 0f dd 1f a3 20 71 c4 .....;Y.P.... q. 343 016 c7 d1 f4 c7 33 c0 68 03 04 22 aa 9a c3 d4 6c 4e ....3.h.."....lN 344 032 d2 82 64 46 07 9f aa 09 14 c2 d7 05 d9 8b 02 a2 ..dF............ 345 048 b5 12 9c d1 de 16 4e b9 cb d0 83 e8 a2 50 3c 4e ......N......P.S. 804 Poly1305 r = 455e9a4057ab6080f47b42c052bac7b 805 Poly1305 s = ff53d53e7875932aebd9751073d6e10a 807 Keystream bytes: 808 9f:7b:e9:5d:01:fd:40:ba:15:e2:8f:fb:36:81:0a:ae: 809 c1:c0:88:3f:09:01:6e:de:dd:8a:d0:87:55:82:03:a5: 810 4e:9e:cb:38:ac:8e:5e:2b:b8:da:b2:0f:fa:db:52:e8: 811 75:04:b2:6e:be:69:6d:4f:60:a4:85:cf:11:b8:1b:59: 812 fc:b1:c4:5f:42:19:ee:ac:ec:6a:de:c3:4e:66:69:78: 813 8e:db:41:c4:9c:a3:01:e1:27:e0:ac:ab:3b:44:b9:cf: 814 5c:86:bb:95:e0:6b:0d:f2:90:1a:b6:45:e4:ab:e6:22: 815 15:38 817 Ciphertext: 818 000 d3 1a 8d 34 64 8e 60 db 7b 86 af bc 53 ef 7e c2 ...4d.`.{...S.~. 819 016 a4 ad ed 51 29 6e 08 fe a9 e2 b5 a7 36 ee 62 d6 ...Q)n......6.b. 820 032 3d be a4 5e 8c a9 67 12 82 fa fb 69 da 92 72 8b =..^..g....i..r. 821 048 1a 71 de 0a 9e 06 0b 29 05 d6 a5 b6 7e cd 3b 36 .q.....)....~.;6 822 064 92 dd bd 7f 2d 77 8b 8c 98 03 ae e3 28 09 1b 58 ...-w......(..X 823 080 fa b3 24 e4 fa d6 75 94 55 85 80 8b 48 31 d7 bc ..$...u.U...H1.. 824 096 3f f4 de f0 8e 4b 7a 9d e5 76 d2 65 86 ce c6 4b ?....Kz..v.e...K 825 112 61 16 a. 827 AEAD Construction for Poly1305: 828 000 50 51 52 53 c0 c1 c2 c3 c4 c5 c6 c7 00 00 00 00 PQRS............ 829 016 d3 1a 8d 34 64 8e 60 db 7b 86 af bc 53 ef 7e c2 ...4d.`.{...S.~. 830 032 a4 ad ed 51 29 6e 08 fe a9 e2 b5 a7 36 ee 62 d6 ...Q)n......6.b. 831 048 3d be a4 5e 8c a9 67 12 82 fa fb 69 da 92 72 8b =..^..g....i..r. 832 064 1a 71 de 0a 9e 06 0b 29 05 d6 a5 b6 7e cd 3b 36 .q.....)....~.;6 833 080 92 dd bd 7f 2d 77 8b 8c 98 03 ae e3 28 09 1b 58 ....-w......(..X 834 096 fa b3 24 e4 fa d6 75 94 55 85 80 8b 48 31 d7 bc ..$...u.U...H1.. 835 112 3f f4 de f0 8e 4b 7a 9d e5 76 d2 65 86 ce c6 4b ?....Kz..v.e...K 836 128 61 16 00 00 00 00 00 00 00 00 00 00 00 00 00 00 a............... 837 144 0c 00 00 00 00 00 00 00 72 00 00 00 00 00 00 00 ........r....... 839 Note the 4 zero bytes in line 000 and the 14 zero bytes in line 128 841 Tag: 842 1a:e1:0b:59:4f:09:e2:6a:7e:90:2e:cb:d0:60:06:91 844 3. Implementation Advice 846 Each block of ChaCha20 involves 16 move operations and one increment 847 operation for loading the state, 80 each of XOR, addition and Roll 848 operations for the rounds, 16 more add operations and 16 XOR 849 operations for protecting the plaintext. Section 2.3 describes the 850 ChaCha block function as "adding the original input words". This 851 implies that before starting the rounds on the ChaCha state, it is 852 copied aside only to be added in later. This would be correct, but 853 it saves a few operations to instead copy the state and do the work 854 on the copy. This way, for the next block you don't need to recreate 855 the state, but only to increment the block counter. This saves 856 approximately 5.5% of the cycles. 858 It is NOT RECOMMENDED to use a generic big number library such as the 859 one in OpenSSL for the arithmetic operations in Poly1305. Such 860 libraries use dynamic allocation to be able to handle any-sized 861 integer, but that flexibility comes at the expense of performance as 862 well as side-channel security. More efficient implementations that 863 run in constant time are available, one of them in DJB's own library, 864 NaCl ([NaCl]). A constant-time but not optimal approach would be to 865 naively implement the arithmetic operations for a 288-bit integers, 866 because even a naive implementation will not exceed 2^288 in the 867 multiplication of (acc+block) and r. An efficient constant-time 868 implementation can be found in the public domain library poly1305- 869 donna ([poly1305_donna]). 871 4. Security Considerations 873 The ChaCha20 cipher is designed to provide 256-bit security. 875 The Poly1305 authenticator is designed to ensure that forged messages 876 are rejected with a probability of 1-(n/(2^102)) for a 16n-byte 877 message, even after sending 2^64 legitimate messages, so it is SUF- 878 CMA in the terminology of [AE]. 880 Proving the security of either of these is beyond the scope of this 881 document. Such proofs are available in the referenced academic 882 papers. 884 The most important security consideration in implementing this draft 885 is the uniqueness of the nonce used in ChaCha20. Counters and LFSRs 886 are both acceptable ways of generating unique nonces, as is 887 encrypting a counter using a 64-bit cipher such as DES. Note that it 888 is not acceptable to use a truncation of a counter encrypted with a 889 128-bit or 256-bit cipher, because such a truncation may repeat after 890 a short time. 892 The Poly1305 key MUST be unpredictable to an attacker. Randomly 893 generating the key would fulfill this requirement, except that 894 Poly1305 is often used in communications protocols, so the receiver 895 should know the key. Pseudo-random number generation such as by 896 encrypting a counter is acceptable. Using ChaCha with a secret key 897 and a nonce is also acceptable. 899 The algorithms presented here were designed to be easy to implement 900 in constant time to avoid side-channel vulnerabilities. The 901 operations used in ChaCha20 are all additions, XORs, and fixed 902 rotations. All of these can and should be implemented in constant 903 time. Access to offsets into the ChaCha state and the number of 904 operations do not depend on any property of the key, eliminating the 905 chance of information about the key leaking through the timing of 906 cache misses. 908 For Poly1305, the operations are addition, multiplication and 909 modulus, all on >128-bit numbers. This can be done in constant time, 910 but a naive implementation (such as using some generic big number 911 library) will not be constant time. For example, if the 912 multiplication is performed as a separate operation from the modulus, 913 the result will some times be under 2^256 and some times be above 914 2^256. Implementers should be careful about timing side-channels for 915 Poly1305 by using the appropriate implementation of these operations. 917 5. IANA Considerations 919 There are no IANA considerations for this document. 921 6. Acknowledgements 923 ChaCha20 and Poly1305 were invented by Daniel J. Bernstein. The AEAD 924 construction and the method of creating the one-time poly1305 key 925 were invented by Adam Langley. 927 Thanks to Robert Ransom and Ilari Liusvaara for their helpful 928 comments and explanations. Thanks to Niels Moeller for suggesting a 929 more efficient AEAD construction. 931 7. References 933 7.1. Normative References 935 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 936 Requirement Levels", BCP 14, RFC 2119, March 1997. 938 [chacha] Bernstein, D., "ChaCha, a variant of Salsa20", Jan 2008. 940 [poly1305] 941 Bernstein, D., "The Poly1305-AES message-authentication 942 code", Mar 2005. 944 7.2. Informative References 946 [AE] Bellare, M. and C. Namprempre, "Authenticated Encryption: 947 Relations among notions and analysis of the generic 948 composition paradigm", 949 . 951 [FIPS-197] 952 National Institute of Standards and Technology, "Advanced 953 Encryption Standard (AES)", FIPS PUB 197, November 2001. 955 [FIPS-46] National Institute of Standards and Technology, "Data 956 Encryption Standard", FIPS PUB 46-2, December 1993, 957 . 959 [NaCl] Bernstein, D., Lange, T., and P. Schwabe, "NaCl: 960 Networking and Cryptography library", 961 . 963 [RFC4868] Kelly, S. and S. Frankel, "Using HMAC-SHA-256, HMAC-SHA- 964 384, and HMAC-SHA-512 with IPsec", RFC 4868, May 2007. 966 [RFC5116] McGrew, D., "An Interface and Algorithms for Authenticated 967 Encryption", RFC 5116, January 2008. 969 [RFC5996] Kaufman, C., Hoffman, P., Nir, Y., and P. Eronen, 970 "Internet Key Exchange Protocol Version 2 (IKEv2)", 971 RFC 5996, September 2010. 973 [poly1305_donna] 974 Floodyberry, A., "Poly1305-donna", 975 . 977 [standby-cipher] 978 McGrew, D., Grieco, A., and Y. Sheffer, "Selection of 979 Future Cryptographic Standards", 980 draft-mcgrew-standby-cipher (work in progress). 982 Appendix A. Additional Test Vectors 984 The sub-sections of this appendix contain more test vectors for the 985 algorithms in the sub-sections of Section 2. 987 A.1. The ChaCha20 Block Functions 988 Test Vector #1: 989 ============== 991 Key: 992 000 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ 993 016 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ 995 Nonce: 996 000 00 00 00 00 00 00 00 00 00 00 00 00 ............ 998 Block Counter = 0 1000 ChaCha State at the end 1001 ade0b876 903df1a0 e56a5d40 28bd8653 1002 b819d2bd 1aed8da0 ccef36a8 c70d778b 1003 7c5941da 8d485751 3fe02477 374ad8b8 1004 f4b8436a 1ca11815 69b687c3 8665eeb2 1006 Keystream: 1007 000 76 b8 e0 ad a0 f1 3d 90 40 5d 6a e5 53 86 bd 28 v.....=.@]j.S..( 1008 016 bd d2 19 b8 a0 8d ed 1a a8 36 ef cc 8b 77 0d c7 .........6...w.. 1009 032 da 41 59 7c 51 57 48 8d 77 24 e0 3f b8 d8 4a 37 .AY|QWH.w$.?..J7 1010 048 6a 43 b8 f4 15 18 a1 1c c3 87 b6 69 b2 ee 65 86 jC.........i..e. 1012 Test Vector #2: 1013 ============== 1015 Key: 1016 000 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ 1017 016 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ 1019 Nonce: 1020 000 00 00 00 00 00 00 00 00 00 00 00 00 ............ 1022 Block Counter = 1 1024 ChaCha State at the end 1025 bee7079f 7a385155 7c97ba98 0d082d73 1026 a0290fcb 6965e348 3e53c612 ed7aee32 1027 7621b729 434ee69c b03371d5 d539d874 1028 281fed31 45fb0a51 1f0ae1ac 6f4d794b 1030 Keystream: 1031 000 9f 07 e7 be 55 51 38 7a 98 ba 97 7c 73 2d 08 0d ....UQ8z...|s-.. 1032 016 cb 0f 29 a0 48 e3 65 69 12 c6 53 3e 32 ee 7a ed ..).H.ei..S>2.z. 1033 032 29 b7 21 76 9c e6 4e 43 d5 71 33 b0 74 d8 39 d5 ).!v..NC.q3.t.9. 1034 048 31 ed 1f 28 51 0a fb 45 ac e1 0a 1f 4b 79 4d 6f 1..(Q..E....KyMo 1035 Test Vector #3: 1036 ============== 1038 Key: 1039 000 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ 1040 016 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 01 ................ 1042 Nonce: 1043 000 00 00 00 00 00 00 00 00 00 00 00 00 ............ 1045 Block Counter = 1 1047 ChaCha State at the end 1048 2452eb3a 9249f8ec 8d829d9b ddd4ceb1 1049 e8252083 60818b01 f38422b8 5aaa49c9 1050 bb00ca8e da3ba7b4 c4b592d1 fdf2732f 1051 4436274e 2561b3c8 ebdd4aa6 a0136c00 1053 Keystream: 1054 000 3a eb 52 24 ec f8 49 92 9b 9d 82 8d b1 ce d4 dd :.R$..I......... 1055 016 83 20 25 e8 01 8b 81 60 b8 22 84 f3 c9 49 aa 5a . %....`."...I.Z 1056 032 8e ca 00 bb b4 a7 3b da d1 92 b5 c4 2f 73 f2 fd ......;...../s.. 1057 048 4e 27 36 44 c8 b3 61 25 a6 4a dd eb 00 6c 13 a0 N'6D..a%.J...l.. 1059 Test Vector #4: 1060 ============== 1062 Key: 1063 000 00 ff 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ 1064 016 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ 1066 Nonce: 1067 000 00 00 00 00 00 00 00 00 00 00 00 00 ............ 1069 Block Counter = 2 1071 ChaCha State at the end 1072 fb4dd572 4bc42ef1 df922636 327f1394 1073 a78dea8f 5e269039 a1bebbc1 caf09aae 1074 a25ab213 48a6b46c 1b9d9bcb 092c5be6 1075 546ca624 1bec45d5 87f47473 96f0992e 1077 Keystream: 1078 000 72 d5 4d fb f1 2e c4 4b 36 26 92 df 94 13 7f 32 r.M....K6&....2 1079 016 8f ea 8d a7 39 90 26 5e c1 bb be a1 ae 9a f0 ca ....9.&^........ 1080 032 13 b2 5a a2 6c b4 a6 48 cb 9b 9d 1b e6 5b 2c 09 ..Z.l..H.....[,. 1081 048 24 a6 6c 54 d5 45 ec 1b 73 74 f4 87 2e 99 f0 96 $.lT.E..st...... 1083 Test Vector #5: 1084 ============== 1086 Key: 1087 000 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ 1088 016 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ 1090 Nonce: 1091 000 00 00 00 00 00 00 00 00 00 00 00 02 ............ 1093 Block Counter = 0 1095 ChaCha State at the end 1096 374dc6c2 3736d58c b904e24a cd3f93ef 1097 88228b1a 96a4dfb3 5b76ab72 c727ee54 1098 0e0e978a f3145c95 1b748ea8 f786c297 1099 99c28f5f 628314e8 398a19fa 6ded1b53 1101 Keystream: 1102 000 c2 c6 4d 37 8c d5 36 37 4a e2 04 b9 ef 93 3f cd ..M7..67J.....?. 1103 016 1a 8b 22 88 b3 df a4 96 72 ab 76 5b 54 ee 27 c7 ..".....r.v[T.'. 1104 032 8a 97 0e 0e 95 5c 14 f3 a8 8e 74 1b 97 c2 86 f7 .....\....t..... 1105 048 5f 8f c2 99 e8 14 83 62 fa 19 8a 39 53 1b ed 6d _......b...9S..m 1107 A.2. ChaCha20 Encryption 1108 Test Vector #1: 1109 ============== 1111 Key: 1112 000 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ 1113 016 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ 1115 Nonce: 1116 000 00 00 00 00 00 00 00 00 00 00 00 00 ............ 1118 Initial Block Counter = 0 1120 Plaintext: 1121 000 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ 1122 016 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ 1123 032 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ 1124 048 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ 1126 Ciphertext: 1127 000 76 b8 e0 ad a0 f1 3d 90 40 5d 6a e5 53 86 bd 28 v.....=.@]j.S..( 1128 016 bd d2 19 b8 a0 8d ed 1a a8 36 ef cc 8b 77 0d c7 .........6...w.. 1129 032 da 41 59 7c 51 57 48 8d 77 24 e0 3f b8 d8 4a 37 .AY|QWH.w$.?..J7 1130 048 6a 43 b8 f4 15 18 a1 1c c3 87 b6 69 b2 ee 65 86 jC.........i..e. 1132 Test Vector #2: 1133 ============== 1135 Key: 1136 000 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ 1137 016 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 01 ................ 1139 Nonce: 1140 000 00 00 00 00 00 00 00 00 00 00 00 02 ............ 1142 Initial Block Counter = 1 1144 Plaintext: 1145 000 41 6e 79 20 73 75 62 6d 69 73 73 69 6f 6e 20 74 Any submission t 1146 016 6f 20 74 68 65 20 49 45 54 46 20 69 6e 74 65 6e o the IETF inten 1147 032 64 65 64 20 62 79 20 74 68 65 20 43 6f 6e 74 72 ded by the Contr 1148 048 69 62 75 74 6f 72 20 66 6f 72 20 70 75 62 6c 69 ibutor for publi 1149 064 63 61 74 69 6f 6e 20 61 73 20 61 6c 6c 20 6f 72 cation as all or 1150 080 20 70 61 72 74 20 6f 66 20 61 6e 20 49 45 54 46 part of an IETF 1151 096 20 49 6e 74 65 72 6e 65 74 2d 44 72 61 66 74 20 Internet-Draft 1152 112 6f 72 20 52 46 43 20 61 6e 64 20 61 6e 79 20 73 or RFC and any s 1153 128 74 61 74 65 6d 65 6e 74 20 6d 61 64 65 20 77 69 tatement made wi 1154 144 74 68 69 6e 20 74 68 65 20 63 6f 6e 74 65 78 74 thin the context 1155 160 20 6f 66 20 61 6e 20 49 45 54 46 20 61 63 74 69 of an IETF acti 1156 176 76 69 74 79 20 69 73 20 63 6f 6e 73 69 64 65 72 vity is consider 1157 192 65 64 20 61 6e 20 22 49 45 54 46 20 43 6f 6e 74 ed an "IETF Cont 1158 208 72 69 62 75 74 69 6f 6e 22 2e 20 53 75 63 68 20 ribution". Such 1159 224 73 74 61 74 65 6d 65 6e 74 73 20 69 6e 63 6c 75 statements inclu 1160 240 64 65 20 6f 72 61 6c 20 73 74 61 74 65 6d 65 6e de oral statemen 1161 256 74 73 20 69 6e 20 49 45 54 46 20 73 65 73 73 69 ts in IETF sessi 1162 272 6f 6e 73 2c 20 61 73 20 77 65 6c 6c 20 61 73 20 ons, as well as 1163 288 77 72 69 74 74 65 6e 20 61 6e 64 20 65 6c 65 63 written and elec 1164 304 74 72 6f 6e 69 63 20 63 6f 6d 6d 75 6e 69 63 61 tronic communica 1165 320 74 69 6f 6e 73 20 6d 61 64 65 20 61 74 20 61 6e tions made at an 1166 336 79 20 74 69 6d 65 20 6f 72 20 70 6c 61 63 65 2c y time or place, 1167 352 20 77 68 69 63 68 20 61 72 65 20 61 64 64 72 65 which are addre 1168 368 73 73 65 64 20 74 6f ssed to 1170 Ciphertext: 1171 000 a3 fb f0 7d f3 fa 2f de 4f 37 6c a2 3e 82 73 70 ...}../.O7l.>.sp 1172 016 41 60 5d 9f 4f 4f 57 bd 8c ff 2c 1d 4b 79 55 ec A`].OOW...,.KyU. 1173 032 2a 97 94 8b d3 72 29 15 c8 f3 d3 37 f7 d3 70 05 *....r)....7..p. 1174 048 0e 9e 96 d6 47 b7 c3 9f 56 e0 31 ca 5e b6 25 0d ....G...V.1.^.%. 1175 064 40 42 e0 27 85 ec ec fa 4b 4b b5 e8 ea d0 44 0e @B.'....KK....D. 1176 080 20 b6 e8 db 09 d8 81 a7 c6 13 2f 42 0e 52 79 50 ........./B.RyP 1177 096 42 bd fa 77 73 d8 a9 05 14 47 b3 29 1c e1 41 1c B..ws....G.)..A. 1178 112 68 04 65 55 2a a6 c4 05 b7 76 4d 5e 87 be a8 5a h.eU*....vM^...Z 1179 128 d0 0f 84 49 ed 8f 72 d0 d6 62 ab 05 26 91 ca 66 ...I..r..b..&..f 1180 144 42 4b c8 6d 2d f8 0e a4 1f 43 ab f9 37 d3 25 9d BK.m-....C..7.%. 1181 160 c4 b2 d0 df b4 8a 6c 91 39 dd d7 f7 69 66 e9 28 ......l.9...if.( 1182 176 e6 35 55 3b a7 6c 5c 87 9d 7b 35 d4 9e b2 e6 2b .5U;.l\..{5....+ 1183 192 08 71 cd ac 63 89 39 e2 5e 8a 1e 0e f9 d5 28 0f .q..c.9.^.....(. 1184 208 a8 ca 32 8b 35 1c 3c 76 59 89 cb cf 3d aa 8b 6c ..2.5.vC.. 1223 080 1a 55 32 05 57 16 ea d6 96 25 68 f8 7d 3f 3f 77 .U2.W....%h.}??w 1224 096 04 c6 a8 d1 bc d1 bf 4d 50 d6 15 4b 6d a7 31 b1 .......MP..Km.1. 1225 112 87 b5 8d fd 72 8a fa 36 75 7a 79 7a c1 88 d1 ....r..6uzyz... 1227 A.3. Poly1305 Message Authentication Code 1229 Notice how in test vector #2 r is equal to zero. The part of the 1230 Poly1305 algorithm where the accumulator is multiplied by r means 1231 that with r equal zero, the tag will be equal to s regardless of the 1232 content of the Text. Fortunately, all the proposed methods of 1233 generating r are such that getting this particular weak key is very 1234 unlikely. 1236 Test Vector #1: 1237 ============== 1239 One-time Poly1305 Key: 1240 000 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ 1241 016 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ 1243 Text to MAC: 1244 000 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ 1245 016 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ 1246 032 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ 1247 048 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ 1249 Tag: 1250 000 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ 1252 Test Vector #2: 1253 ============== 1255 One-time Poly1305 Key: 1256 000 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ 1257 016 36 e5 f6 b5 c5 e0 60 70 f0 ef ca 96 22 7a 86 3e 6.....`p...."z.> 1259 Text to MAC: 1260 000 41 6e 79 20 73 75 62 6d 69 73 73 69 6f 6e 20 74 Any submission t 1261 016 6f 20 74 68 65 20 49 45 54 46 20 69 6e 74 65 6e o the IETF inten 1262 032 64 65 64 20 62 79 20 74 68 65 20 43 6f 6e 74 72 ded by the Contr 1263 048 69 62 75 74 6f 72 20 66 6f 72 20 70 75 62 6c 69 ibutor for publi 1264 064 63 61 74 69 6f 6e 20 61 73 20 61 6c 6c 20 6f 72 cation as all or 1265 080 20 70 61 72 74 20 6f 66 20 61 6e 20 49 45 54 46 part of an IETF 1266 096 20 49 6e 74 65 72 6e 65 74 2d 44 72 61 66 74 20 Internet-Draft 1267 112 6f 72 20 52 46 43 20 61 6e 64 20 61 6e 79 20 73 or RFC and any s 1268 128 74 61 74 65 6d 65 6e 74 20 6d 61 64 65 20 77 69 tatement made wi 1269 144 74 68 69 6e 20 74 68 65 20 63 6f 6e 74 65 78 74 thin the context 1270 160 20 6f 66 20 61 6e 20 49 45 54 46 20 61 63 74 69 of an IETF acti 1271 176 76 69 74 79 20 69 73 20 63 6f 6e 73 69 64 65 72 vity is consider 1272 192 65 64 20 61 6e 20 22 49 45 54 46 20 43 6f 6e 74 ed an "IETF Cont 1273 208 72 69 62 75 74 69 6f 6e 22 2e 20 53 75 63 68 20 ribution". Such 1274 224 73 74 61 74 65 6d 65 6e 74 73 20 69 6e 63 6c 75 statements inclu 1275 240 64 65 20 6f 72 61 6c 20 73 74 61 74 65 6d 65 6e de oral statemen 1276 256 74 73 20 69 6e 20 49 45 54 46 20 73 65 73 73 69 ts in IETF sessi 1277 272 6f 6e 73 2c 20 61 73 20 77 65 6c 6c 20 61 73 20 ons, as well as 1278 288 77 72 69 74 74 65 6e 20 61 6e 64 20 65 6c 65 63 written and elec 1279 304 74 72 6f 6e 69 63 20 63 6f 6d 6d 75 6e 69 63 61 tronic communica 1280 320 74 69 6f 6e 73 20 6d 61 64 65 20 61 74 20 61 6e tions made at an 1281 336 79 20 74 69 6d 65 20 6f 72 20 70 6c 61 63 65 2c y time or place, 1282 352 20 77 68 69 63 68 20 61 72 65 20 61 64 64 72 65 which are addre 1283 368 73 73 65 64 20 74 6f ssed to 1285 Tag: 1286 000 36 e5 f6 b5 c5 e0 60 70 f0 ef ca 96 22 7a 86 3e 6.....`p...."z.> 1287 Test Vector #3: 1288 ============== 1290 One-time Poly1305 Key: 1291 000 36 e5 f6 b5 c5 e0 60 70 f0 ef ca 96 22 7a 86 3e 6.....`p...."z.> 1292 016 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ 1294 Text to MAC: 1295 000 41 6e 79 20 73 75 62 6d 69 73 73 69 6f 6e 20 74 Any submission t 1296 016 6f 20 74 68 65 20 49 45 54 46 20 69 6e 74 65 6e o the IETF inten 1297 032 64 65 64 20 62 79 20 74 68 65 20 43 6f 6e 74 72 ded by the Contr 1298 048 69 62 75 74 6f 72 20 66 6f 72 20 70 75 62 6c 69 ibutor for publi 1299 064 63 61 74 69 6f 6e 20 61 73 20 61 6c 6c 20 6f 72 cation as all or 1300 080 20 70 61 72 74 20 6f 66 20 61 6e 20 49 45 54 46 part of an IETF 1301 096 20 49 6e 74 65 72 6e 65 74 2d 44 72 61 66 74 20 Internet-Draft 1302 112 6f 72 20 52 46 43 20 61 6e 64 20 61 6e 79 20 73 or RFC and any s 1303 128 74 61 74 65 6d 65 6e 74 20 6d 61 64 65 20 77 69 tatement made wi 1304 144 74 68 69 6e 20 74 68 65 20 63 6f 6e 74 65 78 74 thin the context 1305 160 20 6f 66 20 61 6e 20 49 45 54 46 20 61 63 74 69 of an IETF acti 1306 176 76 69 74 79 20 69 73 20 63 6f 6e 73 69 64 65 72 vity is consider 1307 192 65 64 20 61 6e 20 22 49 45 54 46 20 43 6f 6e 74 ed an "IETF Cont 1308 208 72 69 62 75 74 69 6f 6e 22 2e 20 53 75 63 68 20 ribution". Such 1309 224 73 74 61 74 65 6d 65 6e 74 73 20 69 6e 63 6c 75 statements inclu 1310 240 64 65 20 6f 72 61 6c 20 73 74 61 74 65 6d 65 6e de oral statemen 1311 256 74 73 20 69 6e 20 49 45 54 46 20 73 65 73 73 69 ts in IETF sessi 1312 272 6f 6e 73 2c 20 61 73 20 77 65 6c 6c 20 61 73 20 ons, as well as 1313 288 77 72 69 74 74 65 6e 20 61 6e 64 20 65 6c 65 63 written and elec 1314 304 74 72 6f 6e 69 63 20 63 6f 6d 6d 75 6e 69 63 61 tronic communica 1315 320 74 69 6f 6e 73 20 6d 61 64 65 20 61 74 20 61 6e tions made at an 1316 336 79 20 74 69 6d 65 20 6f 72 20 70 6c 61 63 65 2c y time or place, 1317 352 20 77 68 69 63 68 20 61 72 65 20 61 64 64 72 65 which are addre 1318 368 73 73 65 64 20 74 6f ssed to 1320 Tag: 1321 000 f3 47 7e 7c d9 54 17 af 89 a6 b8 79 4c 31 0c f0 .G~|.T.....yL1.. 1323 Test Vector #4: 1324 ============== 1326 One-time Poly1305 Key: 1327 000 1c 92 40 a5 eb 55 d3 8a f3 33 88 86 04 f6 b5 f0 ..@..U...3...... 1328 016 47 39 17 c1 40 2b 80 09 9d ca 5c bc 20 70 75 c0 G9..@+....\. pu. 1330 Text to MAC: 1331 000 27 54 77 61 73 20 62 72 69 6c 6c 69 67 2c 20 61 'Twas brillig, a 1332 016 6e 64 20 74 68 65 20 73 6c 69 74 68 79 20 74 6f nd the slithy to 1333 032 76 65 73 0a 44 69 64 20 67 79 72 65 20 61 6e 64 ves.Did gyre and 1334 048 20 67 69 6d 62 6c 65 20 69 6e 20 74 68 65 20 77 gimble in the w 1335 064 61 62 65 3a 0a 41 6c 6c 20 6d 69 6d 73 79 20 77 abe:.All mimsy w 1336 080 65 72 65 20 74 68 65 20 62 6f 72 6f 67 6f 76 65 ere the borogove 1337 096 73 2c 0a 41 6e 64 20 74 68 65 20 6d 6f 6d 65 20 s,.And the mome 1338 112 72 61 74 68 73 20 6f 75 74 67 72 61 62 65 2e raths outgrabe. 1340 Tag: 1341 000 45 41 66 9a 7e aa ee 61 e7 08 dc 7c bc c5 eb 62 EAf.~..a...|...b 1343 A.4. Poly1305 Key Generation Using ChaCha20 1345 Test Vector #1: 1346 ============== 1348 The key: 1349 000 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ 1350 016 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ 1352 The nonce: 1353 000 00 00 00 00 00 00 00 00 00 00 00 00 ............ 1355 Poly1305 one-time key: 1356 000 76 b8 e0 ad a0 f1 3d 90 40 5d 6a e5 53 86 bd 28 v.....=.@]j.S..( 1357 016 bd d2 19 b8 a0 8d ed 1a a8 36 ef cc 8b 77 0d c7 .........6...w.. 1359 Test Vector #2: 1360 ============== 1362 The key: 1363 000 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ 1364 016 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 01 ................ 1366 The nonce: 1367 000 00 00 00 00 00 00 00 00 00 00 00 02 ............ 1369 Poly1305 one-time key: 1370 000 ec fa 25 4f 84 5f 64 74 73 d3 cb 14 0d a9 e8 76 ..%O._dts......v 1371 016 06 cb 33 06 6c 44 7b 87 bc 26 66 dd e3 fb b7 39 ..3.lD{..&f....9 1373 Test Vector #3: 1374 ============== 1376 The key: 1377 000 1c 92 40 a5 eb 55 d3 8a f3 33 88 86 04 f6 b5 f0 ..@..U...3...... 1378 016 47 39 17 c1 40 2b 80 09 9d ca 5c bc 20 70 75 c0 G9..@+....\. pu. 1380 The nonce: 1381 000 00 00 00 00 00 00 00 00 00 00 00 02 ............ 1383 Poly1305 one-time key: 1384 000 96 5e 3b c6 f9 ec 7e d9 56 08 08 f4 d2 29 f9 4b .^;...~.V....).K 1385 016 13 7f f2 75 ca 9b 3f cb dd 59 de aa d2 33 10 ae ..u..?..Y...3.. 1387 A.5. ChaCha20-Poly1305 AEAD Decryption 1389 Below we'll see decrypting a message. We receive a ciphertext, a 1390 nonce, and a tag. We know the key. We will check the tag, and then 1391 (assuming that it validates) decrypt the ciphertext. In this 1392 particular protocol, we'll assume that there is no padding of the 1393 plaintext. 1395 The key: 1396 000 1c 92 40 a5 eb 55 d3 8a f3 33 88 86 04 f6 b5 f0 ..@..U...3...... 1397 016 47 39 17 c1 40 2b 80 09 9d ca 5c bc 20 70 75 c0 G9..@+....\. pu. 1399 Ciphertext: 1400 000 64 a0 86 15 75 86 1a f4 60 f0 62 c7 9b e6 43 bd d...u...`.b...C. 1401 016 5e 80 5c fd 34 5c f3 89 f1 08 67 0a c7 6c 8c b2 ^.\.4\....g..l.. 1402 032 4c 6c fc 18 75 5d 43 ee a0 9e e9 4e 38 2d 26 b0 Ll..u]C....N8-&. 1403 048 bd b7 b7 3c 32 1b 01 00 d4 f0 3b 7f 35 58 94 cf ...<2.....;.5X.. 1404 064 33 2f 83 0e 71 0b 97 ce 98 c8 a8 4a bd 0b 94 81 3/..q......J.... 1405 080 14 ad 17 6e 00 8d 33 bd 60 f9 82 b1 ff 37 c8 55 ...n..3.`....7.U 1406 096 97 97 a0 6e f4 f0 ef 61 c1 86 32 4e 2b 35 06 38 ...n...a..2N+5.8 1407 112 36 06 90 7b 6a 7c 02 b0 f9 f6 15 7b 53 c8 67 e4 6..{j|.....{S.g. 1408 128 b9 16 6c 76 7b 80 4d 46 a5 9b 52 16 cd e7 a4 e9 ..lv{.MF..R..... 1409 144 90 40 c5 a4 04 33 22 5e e2 82 a1 b0 a0 6c 52 3e .@...3"^.....lR> 1410 160 af 45 34 d7 f8 3f a1 15 5b 00 47 71 8c bc 54 6a .E4..?..[.Gq..Tj 1411 176 0d 07 2b 04 b3 56 4e ea 1b 42 22 73 f5 48 27 1a ..+..VN..B"s.H'. 1412 192 0b b2 31 60 53 fa 76 99 19 55 eb d6 31 59 43 4e ..1`S.v..U..1YCN 1413 208 ce bb 4e 46 6d ae 5a 10 73 a6 72 76 27 09 7a 10 ..NFm.Z.s.rv'.z. 1414 224 49 e6 17 d9 1d 36 10 94 fa 68 f0 ff 77 98 71 30 I....6...h..w.q0 1415 240 30 5b ea ba 2e da 04 df 99 7b 71 4d 6c 6f 2c 29 0[.......{qMlo,) 1416 256 a6 ad 5c b4 02 2b 02 70 9b ..\..+.p. 1418 The nonce: 1419 000 00 00 00 00 01 02 03 04 05 06 07 08 ............ 1421 The AAD: 1422 000 f3 33 88 86 00 00 00 00 00 00 4e 91 .3........N. 1424 Received Tag: 1425 000 ee ad 9d 67 89 0c bb 22 39 23 36 fe a1 85 1f 38 ...g..."9#6....8 1426 First, we calculate the one-time Poly1305 key 1428 @@@ ChaCha state with key set up 1429 61707865 3320646e 79622d32 6b206574 1430 a540921c 8ad355eb 868833f3 f0b5f604 1431 c1173947 09802b40 bc5cca9d c0757020 1432 00000000 00000000 04030201 08070605 1434 @@@ ChaCha state after 20 rounds 1435 a94af0bd 89dee45c b64bb195 afec8fa1 1436 508f4726 63f554c0 1ea2c0db aa721526 1437 11b1e514 a0bacc0f 828a6015 d7825481 1438 e8a4a850 d9dcbbd6 4c2de33a f8ccd912 1440 @@@ out bytes: 1441 bd:f0:4a:a9:5c:e4:de:89:95:b1:4b:b6:a1:8f:ec:af: 1442 26:47:8f:50:c0:54:f5:63:db:c0:a2:1e:26:15:72:aa 1444 Poly1305 one-time key: 1445 000 bd f0 4a a9 5c e4 de 89 95 b1 4b b6 a1 8f ec af ..J.\.....K..... 1446 016 26 47 8f 50 c0 54 f5 63 db c0 a2 1e 26 15 72 aa &G.P.T.c....&.r. 1448 Next, we construct the AEAD buffer 1450 Poly1305 Input: 1451 000 f3 33 88 86 00 00 00 00 00 00 4e 91 00 00 00 00 .3........N..... 1452 016 64 a0 86 15 75 86 1a f4 60 f0 62 c7 9b e6 43 bd d...u...`.b...C. 1453 032 5e 80 5c fd 34 5c f3 89 f1 08 67 0a c7 6c 8c b2 ^.\.4\....g..l.. 1454 048 4c 6c fc 18 75 5d 43 ee a0 9e e9 4e 38 2d 26 b0 Ll..u]C....N8-&. 1455 064 bd b7 b7 3c 32 1b 01 00 d4 f0 3b 7f 35 58 94 cf ...<2.....;.5X.. 1456 080 33 2f 83 0e 71 0b 97 ce 98 c8 a8 4a bd 0b 94 81 3/..q......J.... 1457 096 14 ad 17 6e 00 8d 33 bd 60 f9 82 b1 ff 37 c8 55 ...n..3.`....7.U 1458 112 97 97 a0 6e f4 f0 ef 61 c1 86 32 4e 2b 35 06 38 ...n...a..2N+5.8 1459 128 36 06 90 7b 6a 7c 02 b0 f9 f6 15 7b 53 c8 67 e4 6..{j|.....{S.g. 1460 144 b9 16 6c 76 7b 80 4d 46 a5 9b 52 16 cd e7 a4 e9 ..lv{.MF..R..... 1461 160 90 40 c5 a4 04 33 22 5e e2 82 a1 b0 a0 6c 52 3e .@...3"^.....lR> 1462 176 af 45 34 d7 f8 3f a1 15 5b 00 47 71 8c bc 54 6a .E4..?..[.Gq..Tj 1463 192 0d 07 2b 04 b3 56 4e ea 1b 42 22 73 f5 48 27 1a ..+..VN..B"s.H'. 1464 208 0b b2 31 60 53 fa 76 99 19 55 eb d6 31 59 43 4e ..1`S.v..U..1YCN 1465 224 ce bb 4e 46 6d ae 5a 10 73 a6 72 76 27 09 7a 10 ..NFm.Z.s.rv'.z. 1466 240 49 e6 17 d9 1d 36 10 94 fa 68 f0 ff 77 98 71 30 I....6...h..w.q0 1467 256 30 5b ea ba 2e da 04 df 99 7b 71 4d 6c 6f 2c 29 0[.......{qMlo,) 1468 272 a6 ad 5c b4 02 2b 02 70 9b 00 00 00 00 00 00 00 ..\..+.p........ 1469 288 0c 00 00 00 00 00 00 00 09 01 00 00 00 00 00 00 ................ 1471 We calculate the Poly1305 tag and find that it matches 1473 Calculated Tag: 1474 000 ee ad 9d 67 89 0c bb 22 39 23 36 fe a1 85 1f 38 ...g..."9#6....8 1476 Finally, we decrypt the ciphertext 1478 Plaintext:: 1479 000 49 6e 74 65 72 6e 65 74 2d 44 72 61 66 74 73 20 Internet-Drafts 1480 016 61 72 65 20 64 72 61 66 74 20 64 6f 63 75 6d 65 are draft docume 1481 032 6e 74 73 20 76 61 6c 69 64 20 66 6f 72 20 61 20 nts valid for a 1482 048 6d 61 78 69 6d 75 6d 20 6f 66 20 73 69 78 20 6d maximum of six m 1483 064 6f 6e 74 68 73 20 61 6e 64 20 6d 61 79 20 62 65 onths and may be 1484 080 20 75 70 64 61 74 65 64 2c 20 72 65 70 6c 61 63 updated, replac 1485 096 65 64 2c 20 6f 72 20 6f 62 73 6f 6c 65 74 65 64 ed, or obsoleted 1486 112 20 62 79 20 6f 74 68 65 72 20 64 6f 63 75 6d 65 by other docume 1487 128 6e 74 73 20 61 74 20 61 6e 79 20 74 69 6d 65 2e nts at any time. 1488 144 20 49 74 20 69 73 20 69 6e 61 70 70 72 6f 70 72 It is inappropr 1489 160 69 61 74 65 20 74 6f 20 75 73 65 20 49 6e 74 65 iate to use Inte 1490 176 72 6e 65 74 2d 44 72 61 66 74 73 20 61 73 20 72 rnet-Drafts as r 1491 192 65 66 65 72 65 6e 63 65 20 6d 61 74 65 72 69 61 eference materia 1492 208 6c 20 6f 72 20 74 6f 20 63 69 74 65 20 74 68 65 l or to cite the 1493 224 6d 20 6f 74 68 65 72 20 74 68 61 6e 20 61 73 20 m other than as 1494 240 2f e2 80 9c 77 6f 72 6b 20 69 6e 20 70 72 6f 67 /...work in prog 1495 256 72 65 73 73 2e 2f e2 80 9d ress./... 1497 Authors' Addresses 1499 Yoav Nir 1500 Check Point Software Technologies Ltd. 1501 5 Hasolelim st. 1502 Tel Aviv 6789735 1503 Israel 1505 Email: ynir.ietf@gmail.com 1507 Adam Langley 1508 Google Inc 1510 Email: agl@google.com