Andrew Boyson / crypto

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aes/aes128cbc.c@19:f22327e8be7b, 2019-10-15 (annotated)

Committer:
andrewboyson
Date:
Tue Oct 15 07:26:15 2019 +0000
Revision:
19:f22327e8be7b
Pulled AES128_CBC_SHA1 into its own routines to keep it apart from future work.

Who changed what in which revision?

UserRevisionLine numberNew contents of line
andrewboyson 19:f22327e8be7b 1 /*
andrewboyson 19:f22327e8be7b 2 This is an implementation of the AES algorithm, specifically ECB, CTR and CBC mode.
andrewboyson 19:f22327e8be7b 3 Block size can be chosen in aes.h - available choices are AES128, AES192, AES256.
andrewboyson 19:f22327e8be7b 4 The implementation is verified against the test vectors in:
andrewboyson 19:f22327e8be7b 5 National Institute of Standards and Technology Special Publication 800-38A 2001 ED
andrewboyson 19:f22327e8be7b 6 ECB-AES128
andrewboyson 19:f22327e8be7b 7 ----------
andrewboyson 19:f22327e8be7b 8 plain-text:
andrewboyson 19:f22327e8be7b 9 6bc1bee22e409f96e93d7e117393172a
andrewboyson 19:f22327e8be7b 10 ae2d8a571e03ac9c9eb76fac45af8e51
andrewboyson 19:f22327e8be7b 11 30c81c46a35ce411e5fbc1191a0a52ef
andrewboyson 19:f22327e8be7b 12 f69f2445df4f9b17ad2b417be66c3710
andrewboyson 19:f22327e8be7b 13 key:
andrewboyson 19:f22327e8be7b 14 2b7e151628aed2a6abf7158809cf4f3c
andrewboyson 19:f22327e8be7b 15 resulting cipher
andrewboyson 19:f22327e8be7b 16 3ad77bb40d7a3660a89ecaf32466ef97
andrewboyson 19:f22327e8be7b 17 f5d3d58503b9699de785895a96fdbaaf
andrewboyson 19:f22327e8be7b 18 43b1cd7f598ece23881b00e3ed030688
andrewboyson 19:f22327e8be7b 19 7b0c785e27e8ad3f8223207104725dd4
andrewboyson 19:f22327e8be7b 20 NOTE: String length must be evenly divisible by 16byte (str_len % 16 == 0)
andrewboyson 19:f22327e8be7b 21 You should pad the end of the string with zeros if this is not the case.
andrewboyson 19:f22327e8be7b 22 For AES192/256 the key size is proportionally larger.
andrewboyson 19:f22327e8be7b 23 */
andrewboyson 19:f22327e8be7b 24
andrewboyson 19:f22327e8be7b 25
andrewboyson 19:f22327e8be7b 26 /*****************************************************************************/
andrewboyson 19:f22327e8be7b 27 /* Includes: */
andrewboyson 19:f22327e8be7b 28 /*****************************************************************************/
andrewboyson 19:f22327e8be7b 29 #include <stdint.h>
andrewboyson 19:f22327e8be7b 30 #include <string.h> // CBC mode, for memset
andrewboyson 19:f22327e8be7b 31 #include "aes128cbc.h"
andrewboyson 19:f22327e8be7b 32
andrewboyson 19:f22327e8be7b 33 /*****************************************************************************/
andrewboyson 19:f22327e8be7b 34 /* Defines: */
andrewboyson 19:f22327e8be7b 35 /*****************************************************************************/
andrewboyson 19:f22327e8be7b 36 // The number of columns comprising a state in AES. This is a constant in AES. Value=4
andrewboyson 19:f22327e8be7b 37 #define Nb 4
andrewboyson 19:f22327e8be7b 38
andrewboyson 19:f22327e8be7b 39 #define Nk 4 // The number of 32 bit words in a key.
andrewboyson 19:f22327e8be7b 40 #define Nr 10 // The number of rounds in AES Cipher.
andrewboyson 19:f22327e8be7b 41
andrewboyson 19:f22327e8be7b 42
andrewboyson 19:f22327e8be7b 43 struct Aes128CbcState
andrewboyson 19:f22327e8be7b 44 {
andrewboyson 19:f22327e8be7b 45 uint8_t RoundKey[176];
andrewboyson 19:f22327e8be7b 46 uint8_t Iv[AES128CBC_BLOCK_SIZE];
andrewboyson 19:f22327e8be7b 47 };
andrewboyson 19:f22327e8be7b 48
andrewboyson 19:f22327e8be7b 49 /*****************************************************************************/
andrewboyson 19:f22327e8be7b 50 /* Private variables: */
andrewboyson 19:f22327e8be7b 51 /*****************************************************************************/
andrewboyson 19:f22327e8be7b 52 // state - array holding the intermediate results during decryption.
andrewboyson 19:f22327e8be7b 53 typedef uint8_t state_t[4][4];
andrewboyson 19:f22327e8be7b 54
andrewboyson 19:f22327e8be7b 55 static const uint8_t sbox[256] = {
andrewboyson 19:f22327e8be7b 56 //0 1 2 3 4 5 6 7 8 9 A B C D E F
andrewboyson 19:f22327e8be7b 57 0x63, 0x7c, 0x77, 0x7b, 0xf2, 0x6b, 0x6f, 0xc5, 0x30, 0x01, 0x67, 0x2b, 0xfe, 0xd7, 0xab, 0x76,
andrewboyson 19:f22327e8be7b 58 0xca, 0x82, 0xc9, 0x7d, 0xfa, 0x59, 0x47, 0xf0, 0xad, 0xd4, 0xa2, 0xaf, 0x9c, 0xa4, 0x72, 0xc0,
andrewboyson 19:f22327e8be7b 59 0xb7, 0xfd, 0x93, 0x26, 0x36, 0x3f, 0xf7, 0xcc, 0x34, 0xa5, 0xe5, 0xf1, 0x71, 0xd8, 0x31, 0x15,
andrewboyson 19:f22327e8be7b 60 0x04, 0xc7, 0x23, 0xc3, 0x18, 0x96, 0x05, 0x9a, 0x07, 0x12, 0x80, 0xe2, 0xeb, 0x27, 0xb2, 0x75,
andrewboyson 19:f22327e8be7b 61 0x09, 0x83, 0x2c, 0x1a, 0x1b, 0x6e, 0x5a, 0xa0, 0x52, 0x3b, 0xd6, 0xb3, 0x29, 0xe3, 0x2f, 0x84,
andrewboyson 19:f22327e8be7b 62 0x53, 0xd1, 0x00, 0xed, 0x20, 0xfc, 0xb1, 0x5b, 0x6a, 0xcb, 0xbe, 0x39, 0x4a, 0x4c, 0x58, 0xcf,
andrewboyson 19:f22327e8be7b 63 0xd0, 0xef, 0xaa, 0xfb, 0x43, 0x4d, 0x33, 0x85, 0x45, 0xf9, 0x02, 0x7f, 0x50, 0x3c, 0x9f, 0xa8,
andrewboyson 19:f22327e8be7b 64 0x51, 0xa3, 0x40, 0x8f, 0x92, 0x9d, 0x38, 0xf5, 0xbc, 0xb6, 0xda, 0x21, 0x10, 0xff, 0xf3, 0xd2,
andrewboyson 19:f22327e8be7b 65 0xcd, 0x0c, 0x13, 0xec, 0x5f, 0x97, 0x44, 0x17, 0xc4, 0xa7, 0x7e, 0x3d, 0x64, 0x5d, 0x19, 0x73,
andrewboyson 19:f22327e8be7b 66 0x60, 0x81, 0x4f, 0xdc, 0x22, 0x2a, 0x90, 0x88, 0x46, 0xee, 0xb8, 0x14, 0xde, 0x5e, 0x0b, 0xdb,
andrewboyson 19:f22327e8be7b 67 0xe0, 0x32, 0x3a, 0x0a, 0x49, 0x06, 0x24, 0x5c, 0xc2, 0xd3, 0xac, 0x62, 0x91, 0x95, 0xe4, 0x79,
andrewboyson 19:f22327e8be7b 68 0xe7, 0xc8, 0x37, 0x6d, 0x8d, 0xd5, 0x4e, 0xa9, 0x6c, 0x56, 0xf4, 0xea, 0x65, 0x7a, 0xae, 0x08,
andrewboyson 19:f22327e8be7b 69 0xba, 0x78, 0x25, 0x2e, 0x1c, 0xa6, 0xb4, 0xc6, 0xe8, 0xdd, 0x74, 0x1f, 0x4b, 0xbd, 0x8b, 0x8a,
andrewboyson 19:f22327e8be7b 70 0x70, 0x3e, 0xb5, 0x66, 0x48, 0x03, 0xf6, 0x0e, 0x61, 0x35, 0x57, 0xb9, 0x86, 0xc1, 0x1d, 0x9e,
andrewboyson 19:f22327e8be7b 71 0xe1, 0xf8, 0x98, 0x11, 0x69, 0xd9, 0x8e, 0x94, 0x9b, 0x1e, 0x87, 0xe9, 0xce, 0x55, 0x28, 0xdf,
andrewboyson 19:f22327e8be7b 72 0x8c, 0xa1, 0x89, 0x0d, 0xbf, 0xe6, 0x42, 0x68, 0x41, 0x99, 0x2d, 0x0f, 0xb0, 0x54, 0xbb, 0x16 };
andrewboyson 19:f22327e8be7b 73
andrewboyson 19:f22327e8be7b 74 static const uint8_t rsbox[256] = {
andrewboyson 19:f22327e8be7b 75 0x52, 0x09, 0x6a, 0xd5, 0x30, 0x36, 0xa5, 0x38, 0xbf, 0x40, 0xa3, 0x9e, 0x81, 0xf3, 0xd7, 0xfb,
andrewboyson 19:f22327e8be7b 76 0x7c, 0xe3, 0x39, 0x82, 0x9b, 0x2f, 0xff, 0x87, 0x34, 0x8e, 0x43, 0x44, 0xc4, 0xde, 0xe9, 0xcb,
andrewboyson 19:f22327e8be7b 77 0x54, 0x7b, 0x94, 0x32, 0xa6, 0xc2, 0x23, 0x3d, 0xee, 0x4c, 0x95, 0x0b, 0x42, 0xfa, 0xc3, 0x4e,
andrewboyson 19:f22327e8be7b 78 0x08, 0x2e, 0xa1, 0x66, 0x28, 0xd9, 0x24, 0xb2, 0x76, 0x5b, 0xa2, 0x49, 0x6d, 0x8b, 0xd1, 0x25,
andrewboyson 19:f22327e8be7b 79 0x72, 0xf8, 0xf6, 0x64, 0x86, 0x68, 0x98, 0x16, 0xd4, 0xa4, 0x5c, 0xcc, 0x5d, 0x65, 0xb6, 0x92,
andrewboyson 19:f22327e8be7b 80 0x6c, 0x70, 0x48, 0x50, 0xfd, 0xed, 0xb9, 0xda, 0x5e, 0x15, 0x46, 0x57, 0xa7, 0x8d, 0x9d, 0x84,
andrewboyson 19:f22327e8be7b 81 0x90, 0xd8, 0xab, 0x00, 0x8c, 0xbc, 0xd3, 0x0a, 0xf7, 0xe4, 0x58, 0x05, 0xb8, 0xb3, 0x45, 0x06,
andrewboyson 19:f22327e8be7b 82 0xd0, 0x2c, 0x1e, 0x8f, 0xca, 0x3f, 0x0f, 0x02, 0xc1, 0xaf, 0xbd, 0x03, 0x01, 0x13, 0x8a, 0x6b,
andrewboyson 19:f22327e8be7b 83 0x3a, 0x91, 0x11, 0x41, 0x4f, 0x67, 0xdc, 0xea, 0x97, 0xf2, 0xcf, 0xce, 0xf0, 0xb4, 0xe6, 0x73,
andrewboyson 19:f22327e8be7b 84 0x96, 0xac, 0x74, 0x22, 0xe7, 0xad, 0x35, 0x85, 0xe2, 0xf9, 0x37, 0xe8, 0x1c, 0x75, 0xdf, 0x6e,
andrewboyson 19:f22327e8be7b 85 0x47, 0xf1, 0x1a, 0x71, 0x1d, 0x29, 0xc5, 0x89, 0x6f, 0xb7, 0x62, 0x0e, 0xaa, 0x18, 0xbe, 0x1b,
andrewboyson 19:f22327e8be7b 86 0xfc, 0x56, 0x3e, 0x4b, 0xc6, 0xd2, 0x79, 0x20, 0x9a, 0xdb, 0xc0, 0xfe, 0x78, 0xcd, 0x5a, 0xf4,
andrewboyson 19:f22327e8be7b 87 0x1f, 0xdd, 0xa8, 0x33, 0x88, 0x07, 0xc7, 0x31, 0xb1, 0x12, 0x10, 0x59, 0x27, 0x80, 0xec, 0x5f,
andrewboyson 19:f22327e8be7b 88 0x60, 0x51, 0x7f, 0xa9, 0x19, 0xb5, 0x4a, 0x0d, 0x2d, 0xe5, 0x7a, 0x9f, 0x93, 0xc9, 0x9c, 0xef,
andrewboyson 19:f22327e8be7b 89 0xa0, 0xe0, 0x3b, 0x4d, 0xae, 0x2a, 0xf5, 0xb0, 0xc8, 0xeb, 0xbb, 0x3c, 0x83, 0x53, 0x99, 0x61,
andrewboyson 19:f22327e8be7b 90 0x17, 0x2b, 0x04, 0x7e, 0xba, 0x77, 0xd6, 0x26, 0xe1, 0x69, 0x14, 0x63, 0x55, 0x21, 0x0c, 0x7d };
andrewboyson 19:f22327e8be7b 91
andrewboyson 19:f22327e8be7b 92 // The round constant word array, Rcon[i], contains the values given by
andrewboyson 19:f22327e8be7b 93 // x to the power (i-1) being powers of x (x is denoted as {02}) in the field GF(2^8)
andrewboyson 19:f22327e8be7b 94 static const uint8_t Rcon[11] = { 0x8d, 0x01, 0x02, 0x04, 0x08, 0x10, 0x20, 0x40, 0x80, 0x1b, 0x36 };
andrewboyson 19:f22327e8be7b 95
andrewboyson 19:f22327e8be7b 96 /*
andrewboyson 19:f22327e8be7b 97 * Jordan Goulder points out in PR #12 (https://github.com/kokke/tiny-AES-C/pull/12),
andrewboyson 19:f22327e8be7b 98 * that you can remove most of the elements in the Rcon array, because they are unused.
andrewboyson 19:f22327e8be7b 99 *
andrewboyson 19:f22327e8be7b 100 * From Wikipedia's article on the Rijndael key schedule @ https://en.wikipedia.org/wiki/Rijndael_key_schedule#Rcon
andrewboyson 19:f22327e8be7b 101 *
andrewboyson 19:f22327e8be7b 102 * "Only the first some of these constants are actually used – up to rcon[10] for AES-128 (as 11 round keys are needed),
andrewboyson 19:f22327e8be7b 103 * up to rcon[8] for AES-192, up to rcon[7] for AES-256. rcon[0] is not used in AES algorithm."
andrewboyson 19:f22327e8be7b 104 */
andrewboyson 19:f22327e8be7b 105
andrewboyson 19:f22327e8be7b 106
andrewboyson 19:f22327e8be7b 107 /*****************************************************************************/
andrewboyson 19:f22327e8be7b 108 /* Private functions: */
andrewboyson 19:f22327e8be7b 109 /*****************************************************************************/
andrewboyson 19:f22327e8be7b 110 /*
andrewboyson 19:f22327e8be7b 111 static uint8_t getSBoxValue(uint8_t num)
andrewboyson 19:f22327e8be7b 112 {
andrewboyson 19:f22327e8be7b 113 return sbox[num];
andrewboyson 19:f22327e8be7b 114 }
andrewboyson 19:f22327e8be7b 115 */
andrewboyson 19:f22327e8be7b 116 #define getSBoxValue(num) (sbox[(num)])
andrewboyson 19:f22327e8be7b 117 /*
andrewboyson 19:f22327e8be7b 118 static uint8_t getSBoxInvert(uint8_t num)
andrewboyson 19:f22327e8be7b 119 {
andrewboyson 19:f22327e8be7b 120 return rsbox[num];
andrewboyson 19:f22327e8be7b 121 }
andrewboyson 19:f22327e8be7b 122 */
andrewboyson 19:f22327e8be7b 123 #define getSBoxInvert(num) (rsbox[(num)])
andrewboyson 19:f22327e8be7b 124
andrewboyson 19:f22327e8be7b 125 // This function produces Nb(Nr+1) round keys. The round keys are used in each round to decrypt the states.
andrewboyson 19:f22327e8be7b 126 static void KeyExpansion(uint8_t* RoundKey, const uint8_t* Key)
andrewboyson 19:f22327e8be7b 127 {
andrewboyson 19:f22327e8be7b 128 unsigned i, j, k;
andrewboyson 19:f22327e8be7b 129 uint8_t tempa[4]; // Used for the column/row operations
andrewboyson 19:f22327e8be7b 130
andrewboyson 19:f22327e8be7b 131 // The first round key is the key itself.
andrewboyson 19:f22327e8be7b 132 for (i = 0; i < Nk; ++i)
andrewboyson 19:f22327e8be7b 133 {
andrewboyson 19:f22327e8be7b 134 RoundKey[(i * 4) + 0] = Key[(i * 4) + 0];
andrewboyson 19:f22327e8be7b 135 RoundKey[(i * 4) + 1] = Key[(i * 4) + 1];
andrewboyson 19:f22327e8be7b 136 RoundKey[(i * 4) + 2] = Key[(i * 4) + 2];
andrewboyson 19:f22327e8be7b 137 RoundKey[(i * 4) + 3] = Key[(i * 4) + 3];
andrewboyson 19:f22327e8be7b 138 }
andrewboyson 19:f22327e8be7b 139
andrewboyson 19:f22327e8be7b 140 // All other round keys are found from the previous round keys.
andrewboyson 19:f22327e8be7b 141 for (i = Nk; i < Nb * (Nr + 1); ++i)
andrewboyson 19:f22327e8be7b 142 {
andrewboyson 19:f22327e8be7b 143 {
andrewboyson 19:f22327e8be7b 144 k = (i - 1) * 4;
andrewboyson 19:f22327e8be7b 145 tempa[0]=RoundKey[k + 0];
andrewboyson 19:f22327e8be7b 146 tempa[1]=RoundKey[k + 1];
andrewboyson 19:f22327e8be7b 147 tempa[2]=RoundKey[k + 2];
andrewboyson 19:f22327e8be7b 148 tempa[3]=RoundKey[k + 3];
andrewboyson 19:f22327e8be7b 149
andrewboyson 19:f22327e8be7b 150 }
andrewboyson 19:f22327e8be7b 151
andrewboyson 19:f22327e8be7b 152 if (i % Nk == 0)
andrewboyson 19:f22327e8be7b 153 {
andrewboyson 19:f22327e8be7b 154 // This function shifts the 4 bytes in a word to the left once.
andrewboyson 19:f22327e8be7b 155 // [a0,a1,a2,a3] becomes [a1,a2,a3,a0]
andrewboyson 19:f22327e8be7b 156
andrewboyson 19:f22327e8be7b 157 // Function RotWord()
andrewboyson 19:f22327e8be7b 158 {
andrewboyson 19:f22327e8be7b 159 const uint8_t u8tmp = tempa[0];
andrewboyson 19:f22327e8be7b 160 tempa[0] = tempa[1];
andrewboyson 19:f22327e8be7b 161 tempa[1] = tempa[2];
andrewboyson 19:f22327e8be7b 162 tempa[2] = tempa[3];
andrewboyson 19:f22327e8be7b 163 tempa[3] = u8tmp;
andrewboyson 19:f22327e8be7b 164 }
andrewboyson 19:f22327e8be7b 165
andrewboyson 19:f22327e8be7b 166 // SubWord() is a function that takes a four-byte input word and
andrewboyson 19:f22327e8be7b 167 // applies the S-box to each of the four bytes to produce an output word.
andrewboyson 19:f22327e8be7b 168
andrewboyson 19:f22327e8be7b 169 // Function Subword()
andrewboyson 19:f22327e8be7b 170 {
andrewboyson 19:f22327e8be7b 171 tempa[0] = getSBoxValue(tempa[0]);
andrewboyson 19:f22327e8be7b 172 tempa[1] = getSBoxValue(tempa[1]);
andrewboyson 19:f22327e8be7b 173 tempa[2] = getSBoxValue(tempa[2]);
andrewboyson 19:f22327e8be7b 174 tempa[3] = getSBoxValue(tempa[3]);
andrewboyson 19:f22327e8be7b 175 }
andrewboyson 19:f22327e8be7b 176
andrewboyson 19:f22327e8be7b 177 tempa[0] = tempa[0] ^ Rcon[i/Nk];
andrewboyson 19:f22327e8be7b 178 }
andrewboyson 19:f22327e8be7b 179 j = i * 4; k=(i - Nk) * 4;
andrewboyson 19:f22327e8be7b 180 RoundKey[j + 0] = RoundKey[k + 0] ^ tempa[0];
andrewboyson 19:f22327e8be7b 181 RoundKey[j + 1] = RoundKey[k + 1] ^ tempa[1];
andrewboyson 19:f22327e8be7b 182 RoundKey[j + 2] = RoundKey[k + 2] ^ tempa[2];
andrewboyson 19:f22327e8be7b 183 RoundKey[j + 3] = RoundKey[k + 3] ^ tempa[3];
andrewboyson 19:f22327e8be7b 184 }
andrewboyson 19:f22327e8be7b 185 }
andrewboyson 19:f22327e8be7b 186
andrewboyson 19:f22327e8be7b 187 // This function adds the round key to state.
andrewboyson 19:f22327e8be7b 188 // The round key is added to the state by an XOR function.
andrewboyson 19:f22327e8be7b 189 static void AddRoundKey(uint8_t round, state_t* state, const uint8_t* RoundKey)
andrewboyson 19:f22327e8be7b 190 {
andrewboyson 19:f22327e8be7b 191 uint8_t i,j;
andrewboyson 19:f22327e8be7b 192 for (i = 0; i < 4; ++i)
andrewboyson 19:f22327e8be7b 193 {
andrewboyson 19:f22327e8be7b 194 for (j = 0; j < 4; ++j)
andrewboyson 19:f22327e8be7b 195 {
andrewboyson 19:f22327e8be7b 196 (*state)[i][j] ^= RoundKey[(round * Nb * 4) + (i * Nb) + j];
andrewboyson 19:f22327e8be7b 197 }
andrewboyson 19:f22327e8be7b 198 }
andrewboyson 19:f22327e8be7b 199 }
andrewboyson 19:f22327e8be7b 200
andrewboyson 19:f22327e8be7b 201 // The SubBytes Function Substitutes the values in the
andrewboyson 19:f22327e8be7b 202 // state matrix with values in an S-box.
andrewboyson 19:f22327e8be7b 203 static void SubBytes(state_t* state)
andrewboyson 19:f22327e8be7b 204 {
andrewboyson 19:f22327e8be7b 205 uint8_t i, j;
andrewboyson 19:f22327e8be7b 206 for (i = 0; i < 4; ++i)
andrewboyson 19:f22327e8be7b 207 {
andrewboyson 19:f22327e8be7b 208 for (j = 0; j < 4; ++j)
andrewboyson 19:f22327e8be7b 209 {
andrewboyson 19:f22327e8be7b 210 (*state)[j][i] = getSBoxValue((*state)[j][i]);
andrewboyson 19:f22327e8be7b 211 }
andrewboyson 19:f22327e8be7b 212 }
andrewboyson 19:f22327e8be7b 213 }
andrewboyson 19:f22327e8be7b 214
andrewboyson 19:f22327e8be7b 215 // The ShiftRows() function shifts the rows in the state to the left.
andrewboyson 19:f22327e8be7b 216 // Each row is shifted with different offset.
andrewboyson 19:f22327e8be7b 217 // Offset = Row number. So the first row is not shifted.
andrewboyson 19:f22327e8be7b 218 static void ShiftRows(state_t* state)
andrewboyson 19:f22327e8be7b 219 {
andrewboyson 19:f22327e8be7b 220 uint8_t temp;
andrewboyson 19:f22327e8be7b 221
andrewboyson 19:f22327e8be7b 222 // Rotate first row 1 columns to left
andrewboyson 19:f22327e8be7b 223 temp = (*state)[0][1];
andrewboyson 19:f22327e8be7b 224 (*state)[0][1] = (*state)[1][1];
andrewboyson 19:f22327e8be7b 225 (*state)[1][1] = (*state)[2][1];
andrewboyson 19:f22327e8be7b 226 (*state)[2][1] = (*state)[3][1];
andrewboyson 19:f22327e8be7b 227 (*state)[3][1] = temp;
andrewboyson 19:f22327e8be7b 228
andrewboyson 19:f22327e8be7b 229 // Rotate second row 2 columns to left
andrewboyson 19:f22327e8be7b 230 temp = (*state)[0][2];
andrewboyson 19:f22327e8be7b 231 (*state)[0][2] = (*state)[2][2];
andrewboyson 19:f22327e8be7b 232 (*state)[2][2] = temp;
andrewboyson 19:f22327e8be7b 233
andrewboyson 19:f22327e8be7b 234 temp = (*state)[1][2];
andrewboyson 19:f22327e8be7b 235 (*state)[1][2] = (*state)[3][2];
andrewboyson 19:f22327e8be7b 236 (*state)[3][2] = temp;
andrewboyson 19:f22327e8be7b 237
andrewboyson 19:f22327e8be7b 238 // Rotate third row 3 columns to left
andrewboyson 19:f22327e8be7b 239 temp = (*state)[0][3];
andrewboyson 19:f22327e8be7b 240 (*state)[0][3] = (*state)[3][3];
andrewboyson 19:f22327e8be7b 241 (*state)[3][3] = (*state)[2][3];
andrewboyson 19:f22327e8be7b 242 (*state)[2][3] = (*state)[1][3];
andrewboyson 19:f22327e8be7b 243 (*state)[1][3] = temp;
andrewboyson 19:f22327e8be7b 244 }
andrewboyson 19:f22327e8be7b 245
andrewboyson 19:f22327e8be7b 246 static uint8_t xtime(uint8_t x)
andrewboyson 19:f22327e8be7b 247 {
andrewboyson 19:f22327e8be7b 248 return ((x<<1) ^ (((x>>7) & 1) * 0x1b));
andrewboyson 19:f22327e8be7b 249 }
andrewboyson 19:f22327e8be7b 250
andrewboyson 19:f22327e8be7b 251 // MixColumns function mixes the columns of the state matrix
andrewboyson 19:f22327e8be7b 252 static void MixColumns(state_t* state)
andrewboyson 19:f22327e8be7b 253 {
andrewboyson 19:f22327e8be7b 254 uint8_t i;
andrewboyson 19:f22327e8be7b 255 uint8_t Tmp, Tm, t;
andrewboyson 19:f22327e8be7b 256 for (i = 0; i < 4; ++i)
andrewboyson 19:f22327e8be7b 257 {
andrewboyson 19:f22327e8be7b 258 t = (*state)[i][0];
andrewboyson 19:f22327e8be7b 259 Tmp = (*state)[i][0] ^ (*state)[i][1] ^ (*state)[i][2] ^ (*state)[i][3] ;
andrewboyson 19:f22327e8be7b 260 Tm = (*state)[i][0] ^ (*state)[i][1] ; Tm = xtime(Tm); (*state)[i][0] ^= Tm ^ Tmp ;
andrewboyson 19:f22327e8be7b 261 Tm = (*state)[i][1] ^ (*state)[i][2] ; Tm = xtime(Tm); (*state)[i][1] ^= Tm ^ Tmp ;
andrewboyson 19:f22327e8be7b 262 Tm = (*state)[i][2] ^ (*state)[i][3] ; Tm = xtime(Tm); (*state)[i][2] ^= Tm ^ Tmp ;
andrewboyson 19:f22327e8be7b 263 Tm = (*state)[i][3] ^ t ; Tm = xtime(Tm); (*state)[i][3] ^= Tm ^ Tmp ;
andrewboyson 19:f22327e8be7b 264 }
andrewboyson 19:f22327e8be7b 265 }
andrewboyson 19:f22327e8be7b 266
andrewboyson 19:f22327e8be7b 267 static uint8_t Multiply(uint8_t x, uint8_t y)
andrewboyson 19:f22327e8be7b 268 {
andrewboyson 19:f22327e8be7b 269 return (((y & 1) * x) ^
andrewboyson 19:f22327e8be7b 270 ((y>>1 & 1) * xtime(x)) ^
andrewboyson 19:f22327e8be7b 271 ((y>>2 & 1) * xtime(xtime(x))) ^
andrewboyson 19:f22327e8be7b 272 ((y>>3 & 1) * xtime(xtime(xtime(x)))) ^
andrewboyson 19:f22327e8be7b 273 ((y>>4 & 1) * xtime(xtime(xtime(xtime(x)))))); /* this last call to xtime() can be omitted */
andrewboyson 19:f22327e8be7b 274 }
andrewboyson 19:f22327e8be7b 275
andrewboyson 19:f22327e8be7b 276 // MixColumns function mixes the columns of the state matrix.
andrewboyson 19:f22327e8be7b 277 // The method used to multiply may be difficult to understand for the inexperienced.
andrewboyson 19:f22327e8be7b 278 // Please use the references to gain more information.
andrewboyson 19:f22327e8be7b 279 static void InvMixColumns(state_t* state)
andrewboyson 19:f22327e8be7b 280 {
andrewboyson 19:f22327e8be7b 281 int i;
andrewboyson 19:f22327e8be7b 282 uint8_t a, b, c, d;
andrewboyson 19:f22327e8be7b 283 for (i = 0; i < 4; ++i)
andrewboyson 19:f22327e8be7b 284 {
andrewboyson 19:f22327e8be7b 285 a = (*state)[i][0];
andrewboyson 19:f22327e8be7b 286 b = (*state)[i][1];
andrewboyson 19:f22327e8be7b 287 c = (*state)[i][2];
andrewboyson 19:f22327e8be7b 288 d = (*state)[i][3];
andrewboyson 19:f22327e8be7b 289
andrewboyson 19:f22327e8be7b 290 (*state)[i][0] = Multiply(a, 0x0e) ^ Multiply(b, 0x0b) ^ Multiply(c, 0x0d) ^ Multiply(d, 0x09);
andrewboyson 19:f22327e8be7b 291 (*state)[i][1] = Multiply(a, 0x09) ^ Multiply(b, 0x0e) ^ Multiply(c, 0x0b) ^ Multiply(d, 0x0d);
andrewboyson 19:f22327e8be7b 292 (*state)[i][2] = Multiply(a, 0x0d) ^ Multiply(b, 0x09) ^ Multiply(c, 0x0e) ^ Multiply(d, 0x0b);
andrewboyson 19:f22327e8be7b 293 (*state)[i][3] = Multiply(a, 0x0b) ^ Multiply(b, 0x0d) ^ Multiply(c, 0x09) ^ Multiply(d, 0x0e);
andrewboyson 19:f22327e8be7b 294 }
andrewboyson 19:f22327e8be7b 295 }
andrewboyson 19:f22327e8be7b 296
andrewboyson 19:f22327e8be7b 297
andrewboyson 19:f22327e8be7b 298 // The SubBytes Function Substitutes the values in the
andrewboyson 19:f22327e8be7b 299 // state matrix with values in an S-box.
andrewboyson 19:f22327e8be7b 300 static void InvSubBytes(state_t* state)
andrewboyson 19:f22327e8be7b 301 {
andrewboyson 19:f22327e8be7b 302 uint8_t i, j;
andrewboyson 19:f22327e8be7b 303 for (i = 0; i < 4; ++i)
andrewboyson 19:f22327e8be7b 304 {
andrewboyson 19:f22327e8be7b 305 for (j = 0; j < 4; ++j)
andrewboyson 19:f22327e8be7b 306 {
andrewboyson 19:f22327e8be7b 307 (*state)[j][i] = getSBoxInvert((*state)[j][i]);
andrewboyson 19:f22327e8be7b 308 }
andrewboyson 19:f22327e8be7b 309 }
andrewboyson 19:f22327e8be7b 310 }
andrewboyson 19:f22327e8be7b 311
andrewboyson 19:f22327e8be7b 312 static void InvShiftRows(state_t* state)
andrewboyson 19:f22327e8be7b 313 {
andrewboyson 19:f22327e8be7b 314 uint8_t temp;
andrewboyson 19:f22327e8be7b 315
andrewboyson 19:f22327e8be7b 316 // Rotate first row 1 columns to right
andrewboyson 19:f22327e8be7b 317 temp = (*state)[3][1];
andrewboyson 19:f22327e8be7b 318 (*state)[3][1] = (*state)[2][1];
andrewboyson 19:f22327e8be7b 319 (*state)[2][1] = (*state)[1][1];
andrewboyson 19:f22327e8be7b 320 (*state)[1][1] = (*state)[0][1];
andrewboyson 19:f22327e8be7b 321 (*state)[0][1] = temp;
andrewboyson 19:f22327e8be7b 322
andrewboyson 19:f22327e8be7b 323 // Rotate second row 2 columns to right
andrewboyson 19:f22327e8be7b 324 temp = (*state)[0][2];
andrewboyson 19:f22327e8be7b 325 (*state)[0][2] = (*state)[2][2];
andrewboyson 19:f22327e8be7b 326 (*state)[2][2] = temp;
andrewboyson 19:f22327e8be7b 327
andrewboyson 19:f22327e8be7b 328 temp = (*state)[1][2];
andrewboyson 19:f22327e8be7b 329 (*state)[1][2] = (*state)[3][2];
andrewboyson 19:f22327e8be7b 330 (*state)[3][2] = temp;
andrewboyson 19:f22327e8be7b 331
andrewboyson 19:f22327e8be7b 332 // Rotate third row 3 columns to right
andrewboyson 19:f22327e8be7b 333 temp = (*state)[0][3];
andrewboyson 19:f22327e8be7b 334 (*state)[0][3] = (*state)[1][3];
andrewboyson 19:f22327e8be7b 335 (*state)[1][3] = (*state)[2][3];
andrewboyson 19:f22327e8be7b 336 (*state)[2][3] = (*state)[3][3];
andrewboyson 19:f22327e8be7b 337 (*state)[3][3] = temp;
andrewboyson 19:f22327e8be7b 338 }
andrewboyson 19:f22327e8be7b 339
andrewboyson 19:f22327e8be7b 340 // Cipher is the main function that encrypts the PlainText.
andrewboyson 19:f22327e8be7b 341 static void Cipher(state_t* state, const uint8_t* RoundKey)
andrewboyson 19:f22327e8be7b 342 {
andrewboyson 19:f22327e8be7b 343 uint8_t round = 0;
andrewboyson 19:f22327e8be7b 344
andrewboyson 19:f22327e8be7b 345 // Add the First round key to the state before starting the rounds.
andrewboyson 19:f22327e8be7b 346 AddRoundKey(0, state, RoundKey);
andrewboyson 19:f22327e8be7b 347
andrewboyson 19:f22327e8be7b 348 // There will be Nr rounds.
andrewboyson 19:f22327e8be7b 349 // The first Nr-1 rounds are identical.
andrewboyson 19:f22327e8be7b 350 // These Nr-1 rounds are executed in the loop below.
andrewboyson 19:f22327e8be7b 351 for (round = 1; round < Nr; ++round)
andrewboyson 19:f22327e8be7b 352 {
andrewboyson 19:f22327e8be7b 353 SubBytes(state);
andrewboyson 19:f22327e8be7b 354 ShiftRows(state);
andrewboyson 19:f22327e8be7b 355 MixColumns(state);
andrewboyson 19:f22327e8be7b 356 AddRoundKey(round, state, RoundKey);
andrewboyson 19:f22327e8be7b 357 }
andrewboyson 19:f22327e8be7b 358
andrewboyson 19:f22327e8be7b 359 // The last round is given below.
andrewboyson 19:f22327e8be7b 360 // The MixColumns function is not here in the last round.
andrewboyson 19:f22327e8be7b 361 SubBytes(state);
andrewboyson 19:f22327e8be7b 362 ShiftRows(state);
andrewboyson 19:f22327e8be7b 363 AddRoundKey(Nr, state, RoundKey);
andrewboyson 19:f22327e8be7b 364 }
andrewboyson 19:f22327e8be7b 365
andrewboyson 19:f22327e8be7b 366 static void InvCipher(state_t* state, const uint8_t* RoundKey)
andrewboyson 19:f22327e8be7b 367 {
andrewboyson 19:f22327e8be7b 368 uint8_t round = 0;
andrewboyson 19:f22327e8be7b 369
andrewboyson 19:f22327e8be7b 370 // Add the First round key to the state before starting the rounds.
andrewboyson 19:f22327e8be7b 371 AddRoundKey(Nr, state, RoundKey);
andrewboyson 19:f22327e8be7b 372
andrewboyson 19:f22327e8be7b 373 // There will be Nr rounds.
andrewboyson 19:f22327e8be7b 374 // The first Nr-1 rounds are identical.
andrewboyson 19:f22327e8be7b 375 // These Nr-1 rounds are executed in the loop below.
andrewboyson 19:f22327e8be7b 376 for (round = (Nr - 1); round > 0; --round)
andrewboyson 19:f22327e8be7b 377 {
andrewboyson 19:f22327e8be7b 378 InvShiftRows(state);
andrewboyson 19:f22327e8be7b 379 InvSubBytes(state);
andrewboyson 19:f22327e8be7b 380 AddRoundKey(round, state, RoundKey);
andrewboyson 19:f22327e8be7b 381 InvMixColumns(state);
andrewboyson 19:f22327e8be7b 382 }
andrewboyson 19:f22327e8be7b 383
andrewboyson 19:f22327e8be7b 384 // The last round is given below.
andrewboyson 19:f22327e8be7b 385 // The MixColumns function is not here in the last round.
andrewboyson 19:f22327e8be7b 386 InvShiftRows(state);
andrewboyson 19:f22327e8be7b 387 InvSubBytes(state);
andrewboyson 19:f22327e8be7b 388 AddRoundKey(0, state, RoundKey);
andrewboyson 19:f22327e8be7b 389 }
andrewboyson 19:f22327e8be7b 390
andrewboyson 19:f22327e8be7b 391 /*****************************************************************************/
andrewboyson 19:f22327e8be7b 392 /* Public functions: */
andrewboyson 19:f22327e8be7b 393 /*****************************************************************************/
andrewboyson 19:f22327e8be7b 394
andrewboyson 19:f22327e8be7b 395 static void XorWithIv(uint8_t* buf, const uint8_t* Iv)
andrewboyson 19:f22327e8be7b 396 {
andrewboyson 19:f22327e8be7b 397 uint8_t i;
andrewboyson 19:f22327e8be7b 398 for (i = 0; i < AES128CBC_BLOCK_SIZE; ++i) // The block in AES is always 128bit no matter the key size
andrewboyson 19:f22327e8be7b 399 {
andrewboyson 19:f22327e8be7b 400 buf[i] ^= Iv[i];
andrewboyson 19:f22327e8be7b 401 }
andrewboyson 19:f22327e8be7b 402 }
andrewboyson 19:f22327e8be7b 403
andrewboyson 19:f22327e8be7b 404 static void init(struct Aes128CbcState* ctx, const uint8_t* key, const uint8_t* iv)
andrewboyson 19:f22327e8be7b 405 {
andrewboyson 19:f22327e8be7b 406 KeyExpansion(ctx->RoundKey, key);
andrewboyson 19:f22327e8be7b 407 memcpy (ctx->Iv, iv, AES128CBC_BLOCK_SIZE);
andrewboyson 19:f22327e8be7b 408 }
andrewboyson 19:f22327e8be7b 409
andrewboyson 19:f22327e8be7b 410 static void encrypt(struct Aes128CbcState *ctx, uint8_t* buf, uint32_t length)
andrewboyson 19:f22327e8be7b 411 {
andrewboyson 19:f22327e8be7b 412 uintptr_t i;
andrewboyson 19:f22327e8be7b 413 uint8_t *Iv = ctx->Iv;
andrewboyson 19:f22327e8be7b 414 for (i = 0; i < length; i += AES128CBC_BLOCK_SIZE)
andrewboyson 19:f22327e8be7b 415 {
andrewboyson 19:f22327e8be7b 416 XorWithIv(buf, Iv);
andrewboyson 19:f22327e8be7b 417 Cipher((state_t*)buf, ctx->RoundKey);
andrewboyson 19:f22327e8be7b 418 Iv = buf;
andrewboyson 19:f22327e8be7b 419 buf += AES128CBC_BLOCK_SIZE;
andrewboyson 19:f22327e8be7b 420 }
andrewboyson 19:f22327e8be7b 421 memcpy(ctx->Iv, Iv, AES128CBC_BLOCK_SIZE);
andrewboyson 19:f22327e8be7b 422 }
andrewboyson 19:f22327e8be7b 423
andrewboyson 19:f22327e8be7b 424 static void decrypt(struct Aes128CbcState* ctx, uint8_t* buf, uint32_t length)
andrewboyson 19:f22327e8be7b 425 {
andrewboyson 19:f22327e8be7b 426 uintptr_t i;
andrewboyson 19:f22327e8be7b 427 uint8_t storeNextIv[AES128CBC_BLOCK_SIZE];
andrewboyson 19:f22327e8be7b 428 for (i = 0; i < length; i += AES128CBC_BLOCK_SIZE)
andrewboyson 19:f22327e8be7b 429 {
andrewboyson 19:f22327e8be7b 430 memcpy(storeNextIv, buf, AES128CBC_BLOCK_SIZE);
andrewboyson 19:f22327e8be7b 431 InvCipher((state_t*)buf, ctx->RoundKey);
andrewboyson 19:f22327e8be7b 432 XorWithIv(buf, ctx->Iv);
andrewboyson 19:f22327e8be7b 433 memcpy(ctx->Iv, storeNextIv, AES128CBC_BLOCK_SIZE);
andrewboyson 19:f22327e8be7b 434 buf += AES128CBC_BLOCK_SIZE;
andrewboyson 19:f22327e8be7b 435 }
andrewboyson 19:f22327e8be7b 436 }
andrewboyson 19:f22327e8be7b 437
andrewboyson 19:f22327e8be7b 438 void Aes128CbcEncrypt(const uint8_t* key, const uint8_t* iv, uint8_t* buf, uint32_t length)
andrewboyson 19:f22327e8be7b 439 {
andrewboyson 19:f22327e8be7b 440 struct Aes128CbcState ctx;
andrewboyson 19:f22327e8be7b 441 init(&ctx, key, iv);
andrewboyson 19:f22327e8be7b 442 encrypt(&ctx, buf, length);
andrewboyson 19:f22327e8be7b 443 }
andrewboyson 19:f22327e8be7b 444 void Aes128CbcDecrypt(const uint8_t* key, const uint8_t* iv, uint8_t* buf, uint32_t length)
andrewboyson 19:f22327e8be7b 445 {
andrewboyson 19:f22327e8be7b 446 struct Aes128CbcState ctx;
andrewboyson 19:f22327e8be7b 447 init(&ctx, key, iv);
andrewboyson 19:f22327e8be7b 448 decrypt(&ctx, buf, length);
andrewboyson 19:f22327e8be7b 449 }