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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: December 21, 2014 Google Inc 6 June 19, 2014 8 ChaCha20 and Poly1305 for IETF protocols 9 draft-nir-cfrg-chacha20-poly1305-05 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 December 21, 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. They are fast even in software- 107 only C-language implementations, allowing for much quicker deployment 108 when compared with algorithms such as AES that are significantly 109 accelerated by hardware implementations. 111 This 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 These algorithms have undergone rigorous analysis. Several papers 118 discuss the security of Salsa and ChaCha ([LatinDances], 119 [Zhenqing2012]). 121 1.1. Conventions Used in This Document 123 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 124 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 125 document are to be interpreted as described in [RFC2119]. 127 The description of the ChaCha algorithm will at various time refer to 128 the ChaCha state as a "vector" or as a "matrix". This follows the 129 use of these terms in DJB's paper. The matrix notation is more 130 visually convenient, and gives a better notion as to why some rounds 131 are called "column rounds" while others are called "diagonal rounds". 132 Here's a diagram of how to matrices relate to vectors (using the C 133 language convention of zero being the index origin). 135 0 1 2 3 136 4 5 6 7 137 8 9 10 11 138 12 13 14 15 140 The elements in this vector or matrix are 32-bit unsigned integers. 142 The algorithm name is "ChaCha". "ChaCha20" is a specific instance 143 where 20 "rounds" (or 80 quarter rounds - see Section 2.1) are used. 144 Other variations are defined, with 8 or 12 rounds, but in this 145 document we only describe the 20-round ChaCha, so the names "ChaCha" 146 and "ChaCha20" will be used interchangeably. 148 2. The Algorithms 150 The subsections below describe the algorithms used and the AEAD 151 construction. 153 2.1. The ChaCha Quarter Round 155 The basic operation of the ChaCha algorithm is the quarter round. It 156 operates on four 32-bit unsigned integers, denoted a, b, c, and d. 157 The operation is as follows (in C-like notation): 158 o a += b; d ^= a; d <<<= 16; 159 o c += d; b ^= c; b <<<= 12; 160 o a += b; d ^= a; d <<<= 8; 161 o c += d; b ^= c; b <<<= 7; 162 Where "+" denotes integer addition without carry, "^" denotes a 163 bitwise XOR, and "<<< n" denotes an n-bit left rotation (towards the 164 high bits). 166 For example, let's see the add, XOR and roll operations from the 167 first line with sample numbers: 168 o b = 0x01020304 169 o a = 0x11111111 170 o d = 0x01234567 171 o a = a + b = 0x11111111 + 0x01020304 = 0x12131415 172 o d = d ^ a = 0x01234567 ^ 0x12131415 = 0x13305172 173 o d = d<<<16 = 0x51721330 175 2.1.1. Test Vector for the ChaCha Quarter Round 177 For a test vector, we will use the same numbers as in the example, 178 adding something random for c. 179 o a = 0x11111111 180 o b = 0x01020304 181 o c = 0x9b8d6f43 182 o d = 0x01234567 184 After running a Quarter Round on these 4 numbers, we get these: 185 o a = 0xea2a92f4 186 o b = 0xcb1cf8ce 187 o c = 0x4581472e 188 o d = 0x5881c4bb 190 2.2. A Quarter Round on the ChaCha State 192 The ChaCha state does not have 4 integer numbers, but 16. So the 193 quarter round operation works on only 4 of them - hence the name. 194 Each quarter round operates on 4 pre-determined numbers in the ChaCha 195 state. We will denote by QUATERROUND(x,y,z,w) a quarter-round 196 operation on the numbers at indexes x, y, z, and w of the ChaCha 197 state when viewed as a vector. For example, if we apply 198 QUARTERROUND(1,5,9,13) to a state, this means running the quarter 199 round operation on the elements marked with an asterisk, while 200 leaving the others alone: 202 0 *a 2 3 203 4 *b 6 7 204 8 *c 10 11 205 12 *d 14 15 207 Note that this run of quarter round is part of what is called a 208 "column round". 210 2.2.1. Test Vector for the Quarter Round on the ChaCha state 212 For a test vector, we will use a ChaCha state that was generated 213 randomly: 215 Sample ChaCha State 217 879531e0 c5ecf37d 516461b1 c9a62f8a 218 44c20ef3 3390af7f d9fc690b 2a5f714c 219 53372767 b00a5631 974c541a 359e9963 220 5c971061 3d631689 2098d9d6 91dbd320 222 We will apply the QUARTERROUND(2,7,8,13) operation to this state. 223 For obvious reasons, this one is part of what is called a "diagonal 224 round": 226 After applying QUARTERROUND(2,7,8,13) 228 879531e0 c5ecf37d bdb886dc c9a62f8a 229 44c20ef3 3390af7f d9fc690b cfacafd2 230 e46bea80 b00a5631 974c541a 359e9963 231 5c971061 ccc07c79 2098d9d6 91dbd320 233 Note that only the numbers in positions 2, 7, 8, and 13 changed. 235 2.3. The ChaCha20 block Function 237 The ChaCha block function transforms a ChaCha state by running 238 multiple quarter rounds. 240 The inputs to ChaCha20 are: 241 o A 256-bit key, treated as a concatenation of 8 32-bit little- 242 endian integers. 243 o A 96-bit nonce, treated as a concatenation of 3 32-bit little- 244 endian integers. 245 o A 32-bit block count parameter, treated as a 32-bit little-endian 246 integer. 248 The output is 64 random-looking bytes. 250 The ChaCha algorithm described here uses a 256-bit key. The original 251 algorithm also specified 128-bit keys and 8- and 12-round variants, 252 but these are out of scope for this document. In this section we 253 describe the ChaCha block function. 255 Note also that the original ChaCha had a 64-bit nonce and 64-bit 256 block count. We have modified this here to be more consistent with 257 recommendations in section 3.2 of [RFC5116]. This limits the use of 258 a single (key,nonce) combination to 2^32 blocks, or 256 GB, but that 259 is enough for most uses. In cases where a single key is used by 260 multiple senders, it is important to make sure that they don't use 261 the same nonces. This can be assured by partitioning the nonce space 262 so that the first 32 bits are unique per sender, while the other 64 263 bits come from a counter. 265 The ChaCha20 state is initialized as follows: 266 o The first 4 words (0-3) are constants: 0x61707865, 0x3320646e, 267 0x79622d32, 0x6b206574. 268 o The next 8 words (4-11) are taken from the 256-bit key by reading 269 the bytes in little-endian order, in 4-byte chunks. 270 o Word 12 is a block counter. Since each block is 64-byte, a 32-bit 271 word is enough for 256 Gigabytes of data. 273 o Words 13-15 are a nonce, which should not be repeated for the same 274 key. The 13th word is the first 32 bits of the input nonce taken 275 as a little-endian integer, while the 15th word is the last 32 276 bits. 278 cccccccc cccccccc cccccccc cccccccc 279 kkkkkkkk kkkkkkkk kkkkkkkk kkkkkkkk 280 kkkkkkkk kkkkkkkk kkkkkkkk kkkkkkkk 281 bbbbbbbb nnnnnnnn nnnnnnnn nnnnnnnn 283 c=constant k=key b=blockcount n=nonce 285 ChaCha20 runs 20 rounds, alternating between "column" and "diagonal" 286 rounds. Each round is 4 quarter-rounds, and they are run as follows. 287 Quarter-rounds 1-4 are part of a "column" round, while 5-8 are part 288 of a "diagonal" round: 289 1. QUARTERROUND ( 0, 4, 8,12) 290 2. QUARTERROUND ( 1, 5, 9,13) 291 3. QUARTERROUND ( 2, 6,10,14) 292 4. QUARTERROUND ( 3, 7,11,15) 293 5. QUARTERROUND ( 0, 5,10,15) 294 6. QUARTERROUND ( 1, 6,11,12) 295 7. QUARTERROUND ( 2, 7, 8,13) 296 8. QUARTERROUND ( 3, 4, 9,14) 298 At the end of 20 rounds, we arithmetically add the original input 299 words to the output words, and serialize the result by sequencing the 300 words one-by-one in little-endian order. 302 2.3.1. Test Vector for the ChaCha20 Block Function 304 For a test vector, we will use the following inputs to the ChaCha20 305 block function: 306 o Key = 00:01:02:03:04:05:06:07:08:09:0a:0b:0c:0d:0e:0f:10:11:12:13: 307 14:15:16:17:18:19:1a:1b:1c:1d:1e:1f. The key is a sequence of 308 octets with no particular structure before we copy it into the 309 ChaCha state. 310 o Nonce = (00:00:00:09:00:00:00:4a:00:00:00:00) 311 o Block Count = 1. 313 After setting up the ChaCha state, it looks like this: 315 ChaCha State with the key set up. 317 61707865 3320646e 79622d32 6b206574 318 03020100 07060504 0b0a0908 0f0e0d0c 319 13121110 17161514 1b1a1918 1f1e1d1c 320 00000001 09000000 4a000000 00000000 322 After running 20 rounds (10 column rounds interleaved with 10 323 diagonal rounds), the ChaCha state looks like this: 325 ChaCha State after 20 rounds 327 837778ab e238d763 a67ae21e 5950bb2f 328 c4f2d0c7 fc62bb2f 8fa018fc 3f5ec7b7 329 335271c2 f29489f3 eabda8fc 82e46ebd 330 d19c12b4 b04e16de 9e83d0cb 4e3c50a2 332 Finally we add the original state to the result (simple vector or 333 matrix addition), giving this: 335 ChaCha State at the end of the ChaCha20 operation 337 e4e7f110 15593bd1 1fdd0f50 c47120a3 338 c7f4d1c7 0368c033 9aaa2204 4e6cd4c3 339 466482d2 09aa9f07 05d7c214 a2028bd9 340 d19c12b5 b94e16de e883d0cb 4e3c50a2 342 After we serialize the state, we get this: 344 Serialized Block: 345 000 10 f1 e7 e4 d1 3b 59 15 50 0f dd 1f a3 20 71 c4 .....;Y.P.... q. 346 016 c7 d1 f4 c7 33 c0 68 03 04 22 aa 9a c3 d4 6c 4e ....3.h.."....lN 347 032 d2 82 64 46 07 9f aa 09 14 c2 d7 05 d9 8b 02 a2 ..dF............ 348 048 b5 12 9c d1 de 16 4e b9 cb d0 83 e8 a2 50 3c 4e ......N......P.S. 805 Poly1305 r = 455e9a4057ab6080f47b42c052bac7b 806 Poly1305 s = ff53d53e7875932aebd9751073d6e10a 808 Keystream bytes: 809 9f:7b:e9:5d:01:fd:40:ba:15:e2:8f:fb:36:81:0a:ae: 810 c1:c0:88:3f:09:01:6e:de:dd:8a:d0:87:55:82:03:a5: 811 4e:9e:cb:38:ac:8e:5e:2b:b8:da:b2:0f:fa:db:52:e8: 812 75:04:b2:6e:be:69:6d:4f:60:a4:85:cf:11:b8:1b:59: 813 fc:b1:c4:5f:42:19:ee:ac:ec:6a:de:c3:4e:66:69:78: 814 8e:db:41:c4:9c:a3:01:e1:27:e0:ac:ab:3b:44:b9:cf: 815 5c:86:bb:95:e0:6b:0d:f2:90:1a:b6:45:e4:ab:e6:22: 816 15:38 818 Ciphertext: 819 000 d3 1a 8d 34 64 8e 60 db 7b 86 af bc 53 ef 7e c2 ...4d.`.{...S.~. 820 016 a4 ad ed 51 29 6e 08 fe a9 e2 b5 a7 36 ee 62 d6 ...Q)n......6.b. 821 032 3d be a4 5e 8c a9 67 12 82 fa fb 69 da 92 72 8b =..^..g....i..r. 822 048 1a 71 de 0a 9e 06 0b 29 05 d6 a5 b6 7e cd 3b 36 .q.....)....~.;6 823 064 92 dd bd 7f 2d 77 8b 8c 98 03 ae e3 28 09 1b 58 ...-w......(..X 824 080 fa b3 24 e4 fa d6 75 94 55 85 80 8b 48 31 d7 bc ..$...u.U...H1.. 825 096 3f f4 de f0 8e 4b 7a 9d e5 76 d2 65 86 ce c6 4b ?....Kz..v.e...K 826 112 61 16 a. 828 AEAD Construction for Poly1305: 829 000 50 51 52 53 c0 c1 c2 c3 c4 c5 c6 c7 00 00 00 00 PQRS............ 830 016 d3 1a 8d 34 64 8e 60 db 7b 86 af bc 53 ef 7e c2 ...4d.`.{...S.~. 831 032 a4 ad ed 51 29 6e 08 fe a9 e2 b5 a7 36 ee 62 d6 ...Q)n......6.b. 832 048 3d be a4 5e 8c a9 67 12 82 fa fb 69 da 92 72 8b =..^..g....i..r. 833 064 1a 71 de 0a 9e 06 0b 29 05 d6 a5 b6 7e cd 3b 36 .q.....)....~.;6 834 080 92 dd bd 7f 2d 77 8b 8c 98 03 ae e3 28 09 1b 58 ....-w......(..X 835 096 fa b3 24 e4 fa d6 75 94 55 85 80 8b 48 31 d7 bc ..$...u.U...H1.. 836 112 3f f4 de f0 8e 4b 7a 9d e5 76 d2 65 86 ce c6 4b ?....Kz..v.e...K 837 128 61 16 00 00 00 00 00 00 00 00 00 00 00 00 00 00 a............... 838 144 0c 00 00 00 00 00 00 00 72 00 00 00 00 00 00 00 ........r....... 840 Note the 4 zero bytes in line 000 and the 14 zero bytes in line 128 842 Tag: 843 1a:e1:0b:59:4f:09:e2:6a:7e:90:2e:cb:d0:60:06:91 845 3. Implementation Advice 847 Each block of ChaCha20 involves 16 move operations and one increment 848 operation for loading the state, 80 each of XOR, addition and Roll 849 operations for the rounds, 16 more add operations and 16 XOR 850 operations for protecting the plaintext. Section 2.3 describes the 851 ChaCha block function as "adding the original input words". This 852 implies that before starting the rounds on the ChaCha state, it we 853 copy it aside, only to be added in later. This behaves correctly, 854 but it saves a few operations to instead copy the state and do the 855 work on the copy. This way, for the next block you don't need to 856 recreate the state, but only to increment the block counter. This 857 saves approximately 5.5% of the cycles. 859 It is not recommended to use a generic big number library such as the 860 one in OpenSSL for the arithmetic operations in Poly1305. Such 861 libraries use dynamic allocation to be able to handle any-sized 862 integer, but that flexibility comes at the expense of performance as 863 well as side-channel security. More efficient implementations that 864 run in constant time are available, one of them in DJB's own library, 865 NaCl ([NaCl]). A constant-time but not optimal approach would be to 866 naively implement the arithmetic operations for a 288-bit integers, 867 because even a naive implementation will not exceed 2^288 in the 868 multiplication of (acc+block) and r. An efficient constant-time 869 implementation can be found in the public domain library poly1305- 870 donna ([poly1305_donna]). 872 4. Security Considerations 874 The ChaCha20 cipher is designed to provide 256-bit security. 876 The Poly1305 authenticator is designed to ensure that forged messages 877 are rejected with a probability of 1-(n/(2^102)) for a 16n-byte 878 message, even after sending 2^64 legitimate messages, so it is SUF- 879 CMA in the terminology of [AE]. 881 Proving the security of either of these is beyond the scope of this 882 document. Such proofs are available in the referenced academic 883 papers. 885 The most important security consideration in implementing this draft 886 is the uniqueness of the nonce used in ChaCha20. Counters and LFSRs 887 are both acceptable ways of generating unique nonces, as is 888 encrypting a counter using a 64-bit cipher such as DES. Note that it 889 is not acceptable to use a truncation of a counter encrypted with a 890 128-bit or 256-bit cipher, because such a truncation may repeat after 891 a short time. 893 The Poly1305 key MUST be unpredictable to an attacker. Randomly 894 generating the key would fulfill this requirement, except that 895 Poly1305 is often used in communications protocols, so the receiver 896 should know the key. Pseudo-random number generation such as by 897 encrypting a counter is acceptable. Using ChaCha with a secret key 898 and a nonce is also acceptable. 900 The algorithms presented here were designed to be easy to implement 901 in constant time to avoid side-channel vulnerabilities. The 902 operations used in ChaCha20 are all additions, XORs, and fixed 903 rotations. All of these can and should be implemented in constant 904 time. Access to offsets into the ChaCha state and the number of 905 operations do not depend on any property of the key, eliminating the 906 chance of information about the key leaking through the timing of 907 cache misses. 909 For Poly1305, the operations are addition, multiplication and 910 modulus, all on >128-bit numbers. This can be done in constant time, 911 but a naive implementation (such as using some generic big number 912 library) will not be constant time. For example, if the 913 multiplication is performed as a separate operation from the modulus, 914 the result will some times be under 2^256 and some times be above 915 2^256. Implementers should be careful about timing side-channels for 916 Poly1305 by using the appropriate implementation of these operations. 918 5. IANA Considerations 920 There are no IANA considerations for this document. 922 6. Acknowledgements 924 ChaCha20 and Poly1305 were invented by Daniel J. Bernstein. The AEAD 925 construction and the method of creating the one-time poly1305 key 926 were invented by Adam Langley. 928 Thanks to Robert Ransom and Ilari Liusvaara for their helpful 929 comments and explanations. Thanks to Niels Moeller for suggesting 930 the more efficient AEAD construction in this document. 932 7. References 934 7.1. Normative References 936 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 937 Requirement Levels", BCP 14, RFC 2119, March 1997. 939 [chacha] Bernstein, D., "ChaCha, a variant of Salsa20", Jan 2008. 941 [poly1305] 942 Bernstein, D., "The Poly1305-AES message-authentication 943 code", Mar 2005. 945 7.2. Informative References 947 [AE] Bellare, M. and C. Namprempre, "Authenticated Encryption: 948 Relations among notions and analysis of the generic 949 composition paradigm", 950 . 952 [FIPS-197] 953 National Institute of Standards and Technology, "Advanced 954 Encryption Standard (AES)", FIPS PUB 197, November 2001. 956 [FIPS-46] National Institute of Standards and Technology, "Data 957 Encryption Standard", FIPS PUB 46-2, December 1993, 958 . 960 [LatinDances] 961 Aumasson, J., Fischer, S., Khazaei, S., Meier, W., and C. 962 Rechberger, "New Features of Latin Dances: Analysis of 963 Salsa, ChaCha, and Rumba", Dec 2007. 965 [NaCl] Bernstein, D., Lange, T., and P. Schwabe, "NaCl: 966 Networking and Cryptography library", 967 . 969 [RFC4868] Kelly, S. and S. Frankel, "Using HMAC-SHA-256, HMAC-SHA- 970 384, and HMAC-SHA-512 with IPsec", RFC 4868, May 2007. 972 [RFC5116] McGrew, D., "An Interface and Algorithms for Authenticated 973 Encryption", RFC 5116, January 2008. 975 [RFC5996] Kaufman, C., Hoffman, P., Nir, Y., and P. Eronen, 976 "Internet Key Exchange Protocol Version 2 (IKEv2)", 977 RFC 5996, September 2010. 979 [Zhenqing2012] 980 Zhenqing, S., Bin, Z., Dengguo, F., and W. Wenling, 981 "Improved key recovery attacks on reduced-round salsa20 982 and chacha", 2012. 984 [poly1305_donna] 985 Floodyberry, A., "Poly1305-donna", 986 . 988 [standby-cipher] 989 McGrew, D., Grieco, A., and Y. Sheffer, "Selection of 990 Future Cryptographic Standards", 991 draft-mcgrew-standby-cipher (work in progress). 993 Appendix A. Additional Test Vectors 995 The sub-sections of this appendix contain more test vectors for the 996 algorithms in the sub-sections of Section 2. 998 A.1. The ChaCha20 Block Functions 999 Test Vector #1: 1000 ============== 1002 Key: 1003 000 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ 1004 016 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ 1006 Nonce: 1007 000 00 00 00 00 00 00 00 00 00 00 00 00 ............ 1009 Block Counter = 0 1011 ChaCha State at the end 1012 ade0b876 903df1a0 e56a5d40 28bd8653 1013 b819d2bd 1aed8da0 ccef36a8 c70d778b 1014 7c5941da 8d485751 3fe02477 374ad8b8 1015 f4b8436a 1ca11815 69b687c3 8665eeb2 1017 Keystream: 1018 000 76 b8 e0 ad a0 f1 3d 90 40 5d 6a e5 53 86 bd 28 v.....=.@]j.S..( 1019 016 bd d2 19 b8 a0 8d ed 1a a8 36 ef cc 8b 77 0d c7 .........6...w.. 1020 032 da 41 59 7c 51 57 48 8d 77 24 e0 3f b8 d8 4a 37 .AY|QWH.w$.?..J7 1021 048 6a 43 b8 f4 15 18 a1 1c c3 87 b6 69 b2 ee 65 86 jC.........i..e. 1023 Test Vector #2: 1024 ============== 1026 Key: 1027 000 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ 1028 016 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ 1030 Nonce: 1031 000 00 00 00 00 00 00 00 00 00 00 00 00 ............ 1033 Block Counter = 1 1035 ChaCha State at the end 1036 bee7079f 7a385155 7c97ba98 0d082d73 1037 a0290fcb 6965e348 3e53c612 ed7aee32 1038 7621b729 434ee69c b03371d5 d539d874 1039 281fed31 45fb0a51 1f0ae1ac 6f4d794b 1041 Keystream: 1042 000 9f 07 e7 be 55 51 38 7a 98 ba 97 7c 73 2d 08 0d ....UQ8z...|s-.. 1043 016 cb 0f 29 a0 48 e3 65 69 12 c6 53 3e 32 ee 7a ed ..).H.ei..S>2.z. 1044 032 29 b7 21 76 9c e6 4e 43 d5 71 33 b0 74 d8 39 d5 ).!v..NC.q3.t.9. 1045 048 31 ed 1f 28 51 0a fb 45 ac e1 0a 1f 4b 79 4d 6f 1..(Q..E....KyMo 1046 Test Vector #3: 1047 ============== 1049 Key: 1050 000 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ 1051 016 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 01 ................ 1053 Nonce: 1054 000 00 00 00 00 00 00 00 00 00 00 00 00 ............ 1056 Block Counter = 1 1058 ChaCha State at the end 1059 2452eb3a 9249f8ec 8d829d9b ddd4ceb1 1060 e8252083 60818b01 f38422b8 5aaa49c9 1061 bb00ca8e da3ba7b4 c4b592d1 fdf2732f 1062 4436274e 2561b3c8 ebdd4aa6 a0136c00 1064 Keystream: 1065 000 3a eb 52 24 ec f8 49 92 9b 9d 82 8d b1 ce d4 dd :.R$..I......... 1066 016 83 20 25 e8 01 8b 81 60 b8 22 84 f3 c9 49 aa 5a . %....`."...I.Z 1067 032 8e ca 00 bb b4 a7 3b da d1 92 b5 c4 2f 73 f2 fd ......;...../s.. 1068 048 4e 27 36 44 c8 b3 61 25 a6 4a dd eb 00 6c 13 a0 N'6D..a%.J...l.. 1070 Test Vector #4: 1071 ============== 1073 Key: 1074 000 00 ff 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ 1075 016 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ 1077 Nonce: 1078 000 00 00 00 00 00 00 00 00 00 00 00 00 ............ 1080 Block Counter = 2 1082 ChaCha State at the end 1083 fb4dd572 4bc42ef1 df922636 327f1394 1084 a78dea8f 5e269039 a1bebbc1 caf09aae 1085 a25ab213 48a6b46c 1b9d9bcb 092c5be6 1086 546ca624 1bec45d5 87f47473 96f0992e 1088 Keystream: 1089 000 72 d5 4d fb f1 2e c4 4b 36 26 92 df 94 13 7f 32 r.M....K6&....2 1090 016 8f ea 8d a7 39 90 26 5e c1 bb be a1 ae 9a f0 ca ....9.&^........ 1091 032 13 b2 5a a2 6c b4 a6 48 cb 9b 9d 1b e6 5b 2c 09 ..Z.l..H.....[,. 1092 048 24 a6 6c 54 d5 45 ec 1b 73 74 f4 87 2e 99 f0 96 $.lT.E..st...... 1094 Test Vector #5: 1095 ============== 1097 Key: 1098 000 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ 1099 016 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ 1101 Nonce: 1102 000 00 00 00 00 00 00 00 00 00 00 00 02 ............ 1104 Block Counter = 0 1106 ChaCha State at the end 1107 374dc6c2 3736d58c b904e24a cd3f93ef 1108 88228b1a 96a4dfb3 5b76ab72 c727ee54 1109 0e0e978a f3145c95 1b748ea8 f786c297 1110 99c28f5f 628314e8 398a19fa 6ded1b53 1112 Keystream: 1113 000 c2 c6 4d 37 8c d5 36 37 4a e2 04 b9 ef 93 3f cd ..M7..67J.....?. 1114 016 1a 8b 22 88 b3 df a4 96 72 ab 76 5b 54 ee 27 c7 ..".....r.v[T.'. 1115 032 8a 97 0e 0e 95 5c 14 f3 a8 8e 74 1b 97 c2 86 f7 .....\....t..... 1116 048 5f 8f c2 99 e8 14 83 62 fa 19 8a 39 53 1b ed 6d _......b...9S..m 1118 A.2. ChaCha20 Encryption 1119 Test Vector #1: 1120 ============== 1122 Key: 1123 000 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ 1124 016 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ 1126 Nonce: 1127 000 00 00 00 00 00 00 00 00 00 00 00 00 ............ 1129 Initial Block Counter = 0 1131 Plaintext: 1132 000 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ 1133 016 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ 1134 032 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ 1135 048 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ 1137 Ciphertext: 1138 000 76 b8 e0 ad a0 f1 3d 90 40 5d 6a e5 53 86 bd 28 v.....=.@]j.S..( 1139 016 bd d2 19 b8 a0 8d ed 1a a8 36 ef cc 8b 77 0d c7 .........6...w.. 1140 032 da 41 59 7c 51 57 48 8d 77 24 e0 3f b8 d8 4a 37 .AY|QWH.w$.?..J7 1141 048 6a 43 b8 f4 15 18 a1 1c c3 87 b6 69 b2 ee 65 86 jC.........i..e. 1143 Test Vector #2: 1144 ============== 1146 Key: 1147 000 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ 1148 016 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 01 ................ 1150 Nonce: 1151 000 00 00 00 00 00 00 00 00 00 00 00 02 ............ 1153 Initial Block Counter = 1 1155 Plaintext: 1156 000 41 6e 79 20 73 75 62 6d 69 73 73 69 6f 6e 20 74 Any submission t 1157 016 6f 20 74 68 65 20 49 45 54 46 20 69 6e 74 65 6e o the IETF inten 1158 032 64 65 64 20 62 79 20 74 68 65 20 43 6f 6e 74 72 ded by the Contr 1159 048 69 62 75 74 6f 72 20 66 6f 72 20 70 75 62 6c 69 ibutor for publi 1160 064 63 61 74 69 6f 6e 20 61 73 20 61 6c 6c 20 6f 72 cation as all or 1161 080 20 70 61 72 74 20 6f 66 20 61 6e 20 49 45 54 46 part of an IETF 1162 096 20 49 6e 74 65 72 6e 65 74 2d 44 72 61 66 74 20 Internet-Draft 1163 112 6f 72 20 52 46 43 20 61 6e 64 20 61 6e 79 20 73 or RFC and any s 1164 128 74 61 74 65 6d 65 6e 74 20 6d 61 64 65 20 77 69 tatement made wi 1165 144 74 68 69 6e 20 74 68 65 20 63 6f 6e 74 65 78 74 thin the context 1166 160 20 6f 66 20 61 6e 20 49 45 54 46 20 61 63 74 69 of an IETF acti 1167 176 76 69 74 79 20 69 73 20 63 6f 6e 73 69 64 65 72 vity is consider 1168 192 65 64 20 61 6e 20 22 49 45 54 46 20 43 6f 6e 74 ed an "IETF Cont 1169 208 72 69 62 75 74 69 6f 6e 22 2e 20 53 75 63 68 20 ribution". Such 1170 224 73 74 61 74 65 6d 65 6e 74 73 20 69 6e 63 6c 75 statements inclu 1171 240 64 65 20 6f 72 61 6c 20 73 74 61 74 65 6d 65 6e de oral statemen 1172 256 74 73 20 69 6e 20 49 45 54 46 20 73 65 73 73 69 ts in IETF sessi 1173 272 6f 6e 73 2c 20 61 73 20 77 65 6c 6c 20 61 73 20 ons, as well as 1174 288 77 72 69 74 74 65 6e 20 61 6e 64 20 65 6c 65 63 written and elec 1175 304 74 72 6f 6e 69 63 20 63 6f 6d 6d 75 6e 69 63 61 tronic communica 1176 320 74 69 6f 6e 73 20 6d 61 64 65 20 61 74 20 61 6e tions made at an 1177 336 79 20 74 69 6d 65 20 6f 72 20 70 6c 61 63 65 2c y time or place, 1178 352 20 77 68 69 63 68 20 61 72 65 20 61 64 64 72 65 which are addre 1179 368 73 73 65 64 20 74 6f ssed to 1181 Ciphertext: 1182 000 a3 fb f0 7d f3 fa 2f de 4f 37 6c a2 3e 82 73 70 ...}../.O7l.>.sp 1183 016 41 60 5d 9f 4f 4f 57 bd 8c ff 2c 1d 4b 79 55 ec A`].OOW...,.KyU. 1184 032 2a 97 94 8b d3 72 29 15 c8 f3 d3 37 f7 d3 70 05 *....r)....7..p. 1185 048 0e 9e 96 d6 47 b7 c3 9f 56 e0 31 ca 5e b6 25 0d ....G...V.1.^.%. 1186 064 40 42 e0 27 85 ec ec fa 4b 4b b5 e8 ea d0 44 0e @B.'....KK....D. 1187 080 20 b6 e8 db 09 d8 81 a7 c6 13 2f 42 0e 52 79 50 ........./B.RyP 1188 096 42 bd fa 77 73 d8 a9 05 14 47 b3 29 1c e1 41 1c B..ws....G.)..A. 1189 112 68 04 65 55 2a a6 c4 05 b7 76 4d 5e 87 be a8 5a h.eU*....vM^...Z 1190 128 d0 0f 84 49 ed 8f 72 d0 d6 62 ab 05 26 91 ca 66 ...I..r..b..&..f 1191 144 42 4b c8 6d 2d f8 0e a4 1f 43 ab f9 37 d3 25 9d BK.m-....C..7.%. 1192 160 c4 b2 d0 df b4 8a 6c 91 39 dd d7 f7 69 66 e9 28 ......l.9...if.( 1193 176 e6 35 55 3b a7 6c 5c 87 9d 7b 35 d4 9e b2 e6 2b .5U;.l\..{5....+ 1194 192 08 71 cd ac 63 89 39 e2 5e 8a 1e 0e f9 d5 28 0f .q..c.9.^.....(. 1195 208 a8 ca 32 8b 35 1c 3c 76 59 89 cb cf 3d aa 8b 6c ..2.5.vC.. 1234 080 1a 55 32 05 57 16 ea d6 96 25 68 f8 7d 3f 3f 77 .U2.W....%h.}??w 1235 096 04 c6 a8 d1 bc d1 bf 4d 50 d6 15 4b 6d a7 31 b1 .......MP..Km.1. 1236 112 87 b5 8d fd 72 8a fa 36 75 7a 79 7a c1 88 d1 ....r..6uzyz... 1238 A.3. Poly1305 Message Authentication Code 1240 Notice how in test vector #2 r is equal to zero. The part of the 1241 Poly1305 algorithm where the accumulator is multiplied by r means 1242 that with r equal zero, the tag will be equal to s regardless of the 1243 content of the Text. Fortunately, all the proposed methods of 1244 generating r are such that getting this particular weak key is very 1245 unlikely. 1247 Test Vector #1: 1248 ============== 1250 One-time Poly1305 Key: 1251 000 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ 1252 016 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ 1254 Text to MAC: 1255 000 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ 1256 016 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ 1257 032 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ 1258 048 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ 1260 Tag: 1261 000 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ 1263 Test Vector #2: 1264 ============== 1266 One-time Poly1305 Key: 1267 000 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ 1268 016 36 e5 f6 b5 c5 e0 60 70 f0 ef ca 96 22 7a 86 3e 6.....`p...."z.> 1270 Text to MAC: 1271 000 41 6e 79 20 73 75 62 6d 69 73 73 69 6f 6e 20 74 Any submission t 1272 016 6f 20 74 68 65 20 49 45 54 46 20 69 6e 74 65 6e o the IETF inten 1273 032 64 65 64 20 62 79 20 74 68 65 20 43 6f 6e 74 72 ded by the Contr 1274 048 69 62 75 74 6f 72 20 66 6f 72 20 70 75 62 6c 69 ibutor for publi 1275 064 63 61 74 69 6f 6e 20 61 73 20 61 6c 6c 20 6f 72 cation as all or 1276 080 20 70 61 72 74 20 6f 66 20 61 6e 20 49 45 54 46 part of an IETF 1277 096 20 49 6e 74 65 72 6e 65 74 2d 44 72 61 66 74 20 Internet-Draft 1278 112 6f 72 20 52 46 43 20 61 6e 64 20 61 6e 79 20 73 or RFC and any s 1279 128 74 61 74 65 6d 65 6e 74 20 6d 61 64 65 20 77 69 tatement made wi 1280 144 74 68 69 6e 20 74 68 65 20 63 6f 6e 74 65 78 74 thin the context 1281 160 20 6f 66 20 61 6e 20 49 45 54 46 20 61 63 74 69 of an IETF acti 1282 176 76 69 74 79 20 69 73 20 63 6f 6e 73 69 64 65 72 vity is consider 1283 192 65 64 20 61 6e 20 22 49 45 54 46 20 43 6f 6e 74 ed an "IETF Cont 1284 208 72 69 62 75 74 69 6f 6e 22 2e 20 53 75 63 68 20 ribution". Such 1285 224 73 74 61 74 65 6d 65 6e 74 73 20 69 6e 63 6c 75 statements inclu 1286 240 64 65 20 6f 72 61 6c 20 73 74 61 74 65 6d 65 6e de oral statemen 1287 256 74 73 20 69 6e 20 49 45 54 46 20 73 65 73 73 69 ts in IETF sessi 1288 272 6f 6e 73 2c 20 61 73 20 77 65 6c 6c 20 61 73 20 ons, as well as 1289 288 77 72 69 74 74 65 6e 20 61 6e 64 20 65 6c 65 63 written and elec 1290 304 74 72 6f 6e 69 63 20 63 6f 6d 6d 75 6e 69 63 61 tronic communica 1291 320 74 69 6f 6e 73 20 6d 61 64 65 20 61 74 20 61 6e tions made at an 1292 336 79 20 74 69 6d 65 20 6f 72 20 70 6c 61 63 65 2c y time or place, 1293 352 20 77 68 69 63 68 20 61 72 65 20 61 64 64 72 65 which are addre 1294 368 73 73 65 64 20 74 6f ssed to 1296 Tag: 1297 000 36 e5 f6 b5 c5 e0 60 70 f0 ef ca 96 22 7a 86 3e 6.....`p...."z.> 1298 Test Vector #3: 1299 ============== 1301 One-time Poly1305 Key: 1302 000 36 e5 f6 b5 c5 e0 60 70 f0 ef ca 96 22 7a 86 3e 6.....`p...."z.> 1303 016 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ 1305 Text to MAC: 1306 000 41 6e 79 20 73 75 62 6d 69 73 73 69 6f 6e 20 74 Any submission t 1307 016 6f 20 74 68 65 20 49 45 54 46 20 69 6e 74 65 6e o the IETF inten 1308 032 64 65 64 20 62 79 20 74 68 65 20 43 6f 6e 74 72 ded by the Contr 1309 048 69 62 75 74 6f 72 20 66 6f 72 20 70 75 62 6c 69 ibutor for publi 1310 064 63 61 74 69 6f 6e 20 61 73 20 61 6c 6c 20 6f 72 cation as all or 1311 080 20 70 61 72 74 20 6f 66 20 61 6e 20 49 45 54 46 part of an IETF 1312 096 20 49 6e 74 65 72 6e 65 74 2d 44 72 61 66 74 20 Internet-Draft 1313 112 6f 72 20 52 46 43 20 61 6e 64 20 61 6e 79 20 73 or RFC and any s 1314 128 74 61 74 65 6d 65 6e 74 20 6d 61 64 65 20 77 69 tatement made wi 1315 144 74 68 69 6e 20 74 68 65 20 63 6f 6e 74 65 78 74 thin the context 1316 160 20 6f 66 20 61 6e 20 49 45 54 46 20 61 63 74 69 of an IETF acti 1317 176 76 69 74 79 20 69 73 20 63 6f 6e 73 69 64 65 72 vity is consider 1318 192 65 64 20 61 6e 20 22 49 45 54 46 20 43 6f 6e 74 ed an "IETF Cont 1319 208 72 69 62 75 74 69 6f 6e 22 2e 20 53 75 63 68 20 ribution". Such 1320 224 73 74 61 74 65 6d 65 6e 74 73 20 69 6e 63 6c 75 statements inclu 1321 240 64 65 20 6f 72 61 6c 20 73 74 61 74 65 6d 65 6e de oral statemen 1322 256 74 73 20 69 6e 20 49 45 54 46 20 73 65 73 73 69 ts in IETF sessi 1323 272 6f 6e 73 2c 20 61 73 20 77 65 6c 6c 20 61 73 20 ons, as well as 1324 288 77 72 69 74 74 65 6e 20 61 6e 64 20 65 6c 65 63 written and elec 1325 304 74 72 6f 6e 69 63 20 63 6f 6d 6d 75 6e 69 63 61 tronic communica 1326 320 74 69 6f 6e 73 20 6d 61 64 65 20 61 74 20 61 6e tions made at an 1327 336 79 20 74 69 6d 65 20 6f 72 20 70 6c 61 63 65 2c y time or place, 1328 352 20 77 68 69 63 68 20 61 72 65 20 61 64 64 72 65 which are addre 1329 368 73 73 65 64 20 74 6f ssed to 1331 Tag: 1332 000 f3 47 7e 7c d9 54 17 af 89 a6 b8 79 4c 31 0c f0 .G~|.T.....yL1.. 1334 Test Vector #4: 1335 ============== 1337 One-time Poly1305 Key: 1338 000 1c 92 40 a5 eb 55 d3 8a f3 33 88 86 04 f6 b5 f0 ..@..U...3...... 1339 016 47 39 17 c1 40 2b 80 09 9d ca 5c bc 20 70 75 c0 G9..@+....\. pu. 1341 Text to MAC: 1342 000 27 54 77 61 73 20 62 72 69 6c 6c 69 67 2c 20 61 'Twas brillig, a 1343 016 6e 64 20 74 68 65 20 73 6c 69 74 68 79 20 74 6f nd the slithy to 1344 032 76 65 73 0a 44 69 64 20 67 79 72 65 20 61 6e 64 ves.Did gyre and 1345 048 20 67 69 6d 62 6c 65 20 69 6e 20 74 68 65 20 77 gimble in the w 1346 064 61 62 65 3a 0a 41 6c 6c 20 6d 69 6d 73 79 20 77 abe:.All mimsy w 1347 080 65 72 65 20 74 68 65 20 62 6f 72 6f 67 6f 76 65 ere the borogove 1348 096 73 2c 0a 41 6e 64 20 74 68 65 20 6d 6f 6d 65 20 s,.And the mome 1349 112 72 61 74 68 73 20 6f 75 74 67 72 61 62 65 2e raths outgrabe. 1351 Tag: 1352 000 45 41 66 9a 7e aa ee 61 e7 08 dc 7c bc c5 eb 62 EAf.~..a...|...b 1354 A.4. Poly1305 Key Generation Using ChaCha20 1356 Test Vector #1: 1357 ============== 1359 The key: 1360 000 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ 1361 016 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ 1363 The nonce: 1364 000 00 00 00 00 00 00 00 00 00 00 00 00 ............ 1366 Poly1305 one-time key: 1367 000 76 b8 e0 ad a0 f1 3d 90 40 5d 6a e5 53 86 bd 28 v.....=.@]j.S..( 1368 016 bd d2 19 b8 a0 8d ed 1a a8 36 ef cc 8b 77 0d c7 .........6...w.. 1370 Test Vector #2: 1371 ============== 1373 The key: 1374 000 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ 1375 016 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 01 ................ 1377 The nonce: 1378 000 00 00 00 00 00 00 00 00 00 00 00 02 ............ 1380 Poly1305 one-time key: 1381 000 ec fa 25 4f 84 5f 64 74 73 d3 cb 14 0d a9 e8 76 ..%O._dts......v 1382 016 06 cb 33 06 6c 44 7b 87 bc 26 66 dd e3 fb b7 39 ..3.lD{..&f....9 1384 Test Vector #3: 1385 ============== 1387 The key: 1388 000 1c 92 40 a5 eb 55 d3 8a f3 33 88 86 04 f6 b5 f0 ..@..U...3...... 1389 016 47 39 17 c1 40 2b 80 09 9d ca 5c bc 20 70 75 c0 G9..@+....\. pu. 1391 The nonce: 1392 000 00 00 00 00 00 00 00 00 00 00 00 02 ............ 1394 Poly1305 one-time key: 1395 000 96 5e 3b c6 f9 ec 7e d9 56 08 08 f4 d2 29 f9 4b .^;...~.V....).K 1396 016 13 7f f2 75 ca 9b 3f cb dd 59 de aa d2 33 10 ae ..u..?..Y...3.. 1398 A.5. ChaCha20-Poly1305 AEAD Decryption 1400 Below we'll see decrypting a message. We receive a ciphertext, a 1401 nonce, and a tag. We know the key. We will check the tag, and then 1402 (assuming that it validates) decrypt the ciphertext. In this 1403 particular protocol, we'll assume that there is no padding of the 1404 plaintext. 1406 The key: 1407 000 1c 92 40 a5 eb 55 d3 8a f3 33 88 86 04 f6 b5 f0 ..@..U...3...... 1408 016 47 39 17 c1 40 2b 80 09 9d ca 5c bc 20 70 75 c0 G9..@+....\. pu. 1410 Ciphertext: 1411 000 64 a0 86 15 75 86 1a f4 60 f0 62 c7 9b e6 43 bd d...u...`.b...C. 1412 016 5e 80 5c fd 34 5c f3 89 f1 08 67 0a c7 6c 8c b2 ^.\.4\....g..l.. 1413 032 4c 6c fc 18 75 5d 43 ee a0 9e e9 4e 38 2d 26 b0 Ll..u]C....N8-&. 1414 048 bd b7 b7 3c 32 1b 01 00 d4 f0 3b 7f 35 58 94 cf ...<2.....;.5X.. 1415 064 33 2f 83 0e 71 0b 97 ce 98 c8 a8 4a bd 0b 94 81 3/..q......J.... 1416 080 14 ad 17 6e 00 8d 33 bd 60 f9 82 b1 ff 37 c8 55 ...n..3.`....7.U 1417 096 97 97 a0 6e f4 f0 ef 61 c1 86 32 4e 2b 35 06 38 ...n...a..2N+5.8 1418 112 36 06 90 7b 6a 7c 02 b0 f9 f6 15 7b 53 c8 67 e4 6..{j|.....{S.g. 1419 128 b9 16 6c 76 7b 80 4d 46 a5 9b 52 16 cd e7 a4 e9 ..lv{.MF..R..... 1420 144 90 40 c5 a4 04 33 22 5e e2 82 a1 b0 a0 6c 52 3e .@...3"^.....lR> 1421 160 af 45 34 d7 f8 3f a1 15 5b 00 47 71 8c bc 54 6a .E4..?..[.Gq..Tj 1422 176 0d 07 2b 04 b3 56 4e ea 1b 42 22 73 f5 48 27 1a ..+..VN..B"s.H'. 1423 192 0b b2 31 60 53 fa 76 99 19 55 eb d6 31 59 43 4e ..1`S.v..U..1YCN 1424 208 ce bb 4e 46 6d ae 5a 10 73 a6 72 76 27 09 7a 10 ..NFm.Z.s.rv'.z. 1425 224 49 e6 17 d9 1d 36 10 94 fa 68 f0 ff 77 98 71 30 I....6...h..w.q0 1426 240 30 5b ea ba 2e da 04 df 99 7b 71 4d 6c 6f 2c 29 0[.......{qMlo,) 1427 256 a6 ad 5c b4 02 2b 02 70 9b ..\..+.p. 1429 The nonce: 1430 000 00 00 00 00 01 02 03 04 05 06 07 08 ............ 1432 The AAD: 1433 000 f3 33 88 86 00 00 00 00 00 00 4e 91 .3........N. 1435 Received Tag: 1436 000 ee ad 9d 67 89 0c bb 22 39 23 36 fe a1 85 1f 38 ...g..."9#6....8 1437 First, we calculate the one-time Poly1305 key 1439 @@@ ChaCha state with key set up 1440 61707865 3320646e 79622d32 6b206574 1441 a540921c 8ad355eb 868833f3 f0b5f604 1442 c1173947 09802b40 bc5cca9d c0757020 1443 00000000 00000000 04030201 08070605 1445 @@@ ChaCha state after 20 rounds 1446 a94af0bd 89dee45c b64bb195 afec8fa1 1447 508f4726 63f554c0 1ea2c0db aa721526 1448 11b1e514 a0bacc0f 828a6015 d7825481 1449 e8a4a850 d9dcbbd6 4c2de33a f8ccd912 1451 @@@ out bytes: 1452 bd:f0:4a:a9:5c:e4:de:89:95:b1:4b:b6:a1:8f:ec:af: 1453 26:47:8f:50:c0:54:f5:63:db:c0:a2:1e:26:15:72:aa 1455 Poly1305 one-time key: 1456 000 bd f0 4a a9 5c e4 de 89 95 b1 4b b6 a1 8f ec af ..J.\.....K..... 1457 016 26 47 8f 50 c0 54 f5 63 db c0 a2 1e 26 15 72 aa &G.P.T.c....&.r. 1459 Next, we construct the AEAD buffer 1461 Poly1305 Input: 1462 000 f3 33 88 86 00 00 00 00 00 00 4e 91 00 00 00 00 .3........N..... 1463 016 64 a0 86 15 75 86 1a f4 60 f0 62 c7 9b e6 43 bd d...u...`.b...C. 1464 032 5e 80 5c fd 34 5c f3 89 f1 08 67 0a c7 6c 8c b2 ^.\.4\....g..l.. 1465 048 4c 6c fc 18 75 5d 43 ee a0 9e e9 4e 38 2d 26 b0 Ll..u]C....N8-&. 1466 064 bd b7 b7 3c 32 1b 01 00 d4 f0 3b 7f 35 58 94 cf ...<2.....;.5X.. 1467 080 33 2f 83 0e 71 0b 97 ce 98 c8 a8 4a bd 0b 94 81 3/..q......J.... 1468 096 14 ad 17 6e 00 8d 33 bd 60 f9 82 b1 ff 37 c8 55 ...n..3.`....7.U 1469 112 97 97 a0 6e f4 f0 ef 61 c1 86 32 4e 2b 35 06 38 ...n...a..2N+5.8 1470 128 36 06 90 7b 6a 7c 02 b0 f9 f6 15 7b 53 c8 67 e4 6..{j|.....{S.g. 1471 144 b9 16 6c 76 7b 80 4d 46 a5 9b 52 16 cd e7 a4 e9 ..lv{.MF..R..... 1472 160 90 40 c5 a4 04 33 22 5e e2 82 a1 b0 a0 6c 52 3e .@...3"^.....lR> 1473 176 af 45 34 d7 f8 3f a1 15 5b 00 47 71 8c bc 54 6a .E4..?..[.Gq..Tj 1474 192 0d 07 2b 04 b3 56 4e ea 1b 42 22 73 f5 48 27 1a ..+..VN..B"s.H'. 1475 208 0b b2 31 60 53 fa 76 99 19 55 eb d6 31 59 43 4e ..1`S.v..U..1YCN 1476 224 ce bb 4e 46 6d ae 5a 10 73 a6 72 76 27 09 7a 10 ..NFm.Z.s.rv'.z. 1477 240 49 e6 17 d9 1d 36 10 94 fa 68 f0 ff 77 98 71 30 I....6...h..w.q0 1478 256 30 5b ea ba 2e da 04 df 99 7b 71 4d 6c 6f 2c 29 0[.......{qMlo,) 1479 272 a6 ad 5c b4 02 2b 02 70 9b 00 00 00 00 00 00 00 ..\..+.p........ 1480 288 0c 00 00 00 00 00 00 00 09 01 00 00 00 00 00 00 ................ 1482 We calculate the Poly1305 tag and find that it matches 1484 Calculated Tag: 1485 000 ee ad 9d 67 89 0c bb 22 39 23 36 fe a1 85 1f 38 ...g..."9#6....8 1487 Finally, we decrypt the ciphertext 1489 Plaintext:: 1490 000 49 6e 74 65 72 6e 65 74 2d 44 72 61 66 74 73 20 Internet-Drafts 1491 016 61 72 65 20 64 72 61 66 74 20 64 6f 63 75 6d 65 are draft docume 1492 032 6e 74 73 20 76 61 6c 69 64 20 66 6f 72 20 61 20 nts valid for a 1493 048 6d 61 78 69 6d 75 6d 20 6f 66 20 73 69 78 20 6d maximum of six m 1494 064 6f 6e 74 68 73 20 61 6e 64 20 6d 61 79 20 62 65 onths and may be 1495 080 20 75 70 64 61 74 65 64 2c 20 72 65 70 6c 61 63 updated, replac 1496 096 65 64 2c 20 6f 72 20 6f 62 73 6f 6c 65 74 65 64 ed, or obsoleted 1497 112 20 62 79 20 6f 74 68 65 72 20 64 6f 63 75 6d 65 by other docume 1498 128 6e 74 73 20 61 74 20 61 6e 79 20 74 69 6d 65 2e nts at any time. 1499 144 20 49 74 20 69 73 20 69 6e 61 70 70 72 6f 70 72 It is inappropr 1500 160 69 61 74 65 20 74 6f 20 75 73 65 20 49 6e 74 65 iate to use Inte 1501 176 72 6e 65 74 2d 44 72 61 66 74 73 20 61 73 20 72 rnet-Drafts as r 1502 192 65 66 65 72 65 6e 63 65 20 6d 61 74 65 72 69 61 eference materia 1503 208 6c 20 6f 72 20 74 6f 20 63 69 74 65 20 74 68 65 l or to cite the 1504 224 6d 20 6f 74 68 65 72 20 74 68 61 6e 20 61 73 20 m other than as 1505 240 2f e2 80 9c 77 6f 72 6b 20 69 6e 20 70 72 6f 67 /...work in prog 1506 256 72 65 73 73 2e 2f e2 80 9d ress./... 1508 Authors' Addresses 1510 Yoav Nir 1511 Check Point Software Technologies Ltd. 1512 5 Hasolelim st. 1513 Tel Aviv 6789735 1514 Israel 1516 Email: ynir.ietf@gmail.com 1518 Adam Langley 1519 Google Inc 1521 Email: agl@google.com