flight/libraries/aes.c

   1 // http://gladman.plushost.co.uk/oldsite/AES/index.php
   2
   3 #include <stdint.h>
   4
   5 #include "aes.h"
   6
   7 #define BPOLY 0x1B
   8 #define DPOLY 0x8D
   9
  10 const uint8_t sbox[256] = {
  11     0x63, 0x7c, 0x77, 0x7b, 0xf2, 0x6b, 0x6f, 0xc5, 0x30, 0x01, 0x67, 0x2b, 0xfe, 0xd7, 0xab, 0x76,
  12     0xca, 0x82, 0xc9, 0x7d, 0xfa, 0x59, 0x47, 0xf0, 0xad, 0xd4, 0xa2, 0xaf, 0x9c, 0xa4, 0x72, 0xc0,
  13     0xb7, 0xfd, 0x93, 0x26, 0x36, 0x3f, 0xf7, 0xcc, 0x34, 0xa5, 0xe5, 0xf1, 0x71, 0xd8, 0x31, 0x15,
  14     0x04, 0xc7, 0x23, 0xc3, 0x18, 0x96, 0x05, 0x9a, 0x07, 0x12, 0x80, 0xe2, 0xeb, 0x27, 0xb2, 0x75,
  15     0x09, 0x83, 0x2c, 0x1a, 0x1b, 0x6e, 0x5a, 0xa0, 0x52, 0x3b, 0xd6, 0xb3, 0x29, 0xe3, 0x2f, 0x84,
  16     0x53, 0xd1, 0x00, 0xed, 0x20, 0xfc, 0xb1, 0x5b, 0x6a, 0xcb, 0xbe, 0x39, 0x4a, 0x4c, 0x58, 0xcf,
  17     0xd0, 0xef, 0xaa, 0xfb, 0x43, 0x4d, 0x33, 0x85, 0x45, 0xf9, 0x02, 0x7f, 0x50, 0x3c, 0x9f, 0xa8,
  18     0x51, 0xa3, 0x40, 0x8f, 0x92, 0x9d, 0x38, 0xf5, 0xbc, 0xb6, 0xda, 0x21, 0x10, 0xff, 0xf3, 0xd2,
  19     0xcd, 0x0c, 0x13, 0xec, 0x5f, 0x97, 0x44, 0x17, 0xc4, 0xa7, 0x7e, 0x3d, 0x64, 0x5d, 0x19, 0x73,
  20     0x60, 0x81, 0x4f, 0xdc, 0x22, 0x2a, 0x90, 0x88, 0x46, 0xee, 0xb8, 0x14, 0xde, 0x5e, 0x0b, 0xdb,
  21     0xe0, 0x32, 0x3a, 0x0a, 0x49, 0x06, 0x24, 0x5c, 0xc2, 0xd3, 0xac, 0x62, 0x91, 0x95, 0xe4, 0x79,
  22     0xe7, 0xc8, 0x37, 0x6d, 0x8d, 0xd5, 0x4e, 0xa9, 0x6c, 0x56, 0xf4, 0xea, 0x65, 0x7a, 0xae, 0x08,
  23     0xba, 0x78, 0x25, 0x2e, 0x1c, 0xa6, 0xb4, 0xc6, 0xe8, 0xdd, 0x74, 0x1f, 0x4b, 0xbd, 0x8b, 0x8a,
  24     0x70, 0x3e, 0xb5, 0x66, 0x48, 0x03, 0xf6, 0x0e, 0x61, 0x35, 0x57, 0xb9, 0x86, 0xc1, 0x1d, 0x9e,
  25     0xe1, 0xf8, 0x98, 0x11, 0x69, 0xd9, 0x8e, 0x94, 0x9b, 0x1e, 0x87, 0xe9, 0xce, 0x55, 0x28, 0xdf,
  26     0x8c, 0xa1, 0x89, 0x0d, 0xbf, 0xe6, 0x42, 0x68, 0x41, 0x99, 0x2d, 0x0f, 0xb0, 0x54, 0xbb, 0x16
  27 };
  28
  29 const uint8_t isbox[256] = {
  30     0x52, 0x09, 0x6a, 0xd5, 0x30, 0x36, 0xa5, 0x38, 0xbf, 0x40, 0xa3, 0x9e, 0x81, 0xf3, 0xd7, 0xfb,
  31     0x7c, 0xe3, 0x39, 0x82, 0x9b, 0x2f, 0xff, 0x87, 0x34, 0x8e, 0x43, 0x44, 0xc4, 0xde, 0xe9, 0xcb,
  32     0x54, 0x7b, 0x94, 0x32, 0xa6, 0xc2, 0x23, 0x3d, 0xee, 0x4c, 0x95, 0x0b, 0x42, 0xfa, 0xc3, 0x4e,
  33     0x08, 0x2e, 0xa1, 0x66, 0x28, 0xd9, 0x24, 0xb2, 0x76, 0x5b, 0xa2, 0x49, 0x6d, 0x8b, 0xd1, 0x25,
  34     0x72, 0xf8, 0xf6, 0x64, 0x86, 0x68, 0x98, 0x16, 0xd4, 0xa4, 0x5c, 0xcc, 0x5d, 0x65, 0xb6, 0x92,
  35     0x6c, 0x70, 0x48, 0x50, 0xfd, 0xed, 0xb9, 0xda, 0x5e, 0x15, 0x46, 0x57, 0xa7, 0x8d, 0x9d, 0x84,
  36     0x90, 0xd8, 0xab, 0x00, 0x8c, 0xbc, 0xd3, 0x0a, 0xf7, 0xe4, 0x58, 0x05, 0xb8, 0xb3, 0x45, 0x06,
  37     0xd0, 0x2c, 0x1e, 0x8f, 0xca, 0x3f, 0x0f, 0x02, 0xc1, 0xaf, 0xbd, 0x03, 0x01, 0x13, 0x8a, 0x6b,
  38     0x3a, 0x91, 0x11, 0x41, 0x4f, 0x67, 0xdc, 0xea, 0x97, 0xf2, 0xcf, 0xce, 0xf0, 0xb4, 0xe6, 0x73,
  39     0x96, 0xac, 0x74, 0x22, 0xe7, 0xad, 0x35, 0x85, 0xe2, 0xf9, 0x37, 0xe8, 0x1c, 0x75, 0xdf, 0x6e,
  40     0x47, 0xf1, 0x1a, 0x71, 0x1d, 0x29, 0xc5, 0x89, 0x6f, 0xb7, 0x62, 0x0e, 0xaa, 0x18, 0xbe, 0x1b,
  41     0xfc, 0x56, 0x3e, 0x4b, 0xc6, 0xd2, 0x79, 0x20, 0x9a, 0xdb, 0xc0, 0xfe, 0x78, 0xcd, 0x5a, 0xf4,
  42     0x1f, 0xdd, 0xa8, 0x33, 0x88, 0x07, 0xc7, 0x31, 0xb1, 0x12, 0x10, 0x59, 0x27, 0x80, 0xec, 0x5f,
  43     0x60, 0x51, 0x7f, 0xa9, 0x19, 0xb5, 0x4a, 0x0d, 0x2d, 0xe5, 0x7a, 0x9f, 0x93, 0xc9, 0x9c, 0xef,
  44     0xa0, 0xe0, 0x3b, 0x4d, 0xae, 0x2a, 0xf5, 0xb0, 0xc8, 0xeb, 0xbb, 0x3c, 0x83, 0x53, 0x99, 0x61,
  45     0x17, 0x2b, 0x04, 0x7e, 0xba, 0x77, 0xd6, 0x26, 0xe1, 0x69, 0x14, 0x63, 0x55, 0x21, 0x0c, 0x7d
  46 };
  47
  48 // #define xtime(x)     ( (x << 1) ^ (((x >> 7) & 1) * BPOLY) )
  49 // #define xtime(x)     ( (x << 1) ^ ((x & 0x80) ? BPOLY : 0) )
  50
  51 const uint8_t xtime[256] = {
  52     0x00, 0x02, 0x04, 0x06, 0x08, 0x0a, 0x0c, 0x0e, 0x10, 0x12, 0x14, 0x16, 0x18, 0x1a, 0x1c, 0x1e,
  53     0x20, 0x22, 0x24, 0x26, 0x28, 0x2a, 0x2c, 0x2e, 0x30, 0x32, 0x34, 0x36, 0x38, 0x3a, 0x3c, 0x3e,
  54     0x40, 0x42, 0x44, 0x46, 0x48, 0x4a, 0x4c, 0x4e, 0x50, 0x52, 0x54, 0x56, 0x58, 0x5a, 0x5c, 0x5e,
  55     0x60, 0x62, 0x64, 0x66, 0x68, 0x6a, 0x6c, 0x6e, 0x70, 0x72, 0x74, 0x76, 0x78, 0x7a, 0x7c, 0x7e,
  56     0x80, 0x82, 0x84, 0x86, 0x88, 0x8a, 0x8c, 0x8e, 0x90, 0x92, 0x94, 0x96, 0x98, 0x9a, 0x9c, 0x9e,
  57     0xa0, 0xa2, 0xa4, 0xa6, 0xa8, 0xaa, 0xac, 0xae, 0xb0, 0xb2, 0xb4, 0xb6, 0xb8, 0xba, 0xbc, 0xbe,
  58     0xc0, 0xc2, 0xc4, 0xc6, 0xc8, 0xca, 0xcc, 0xce, 0xd0, 0xd2, 0xd4, 0xd6, 0xd8, 0xda, 0xdc, 0xde,
  59     0xe0, 0xe2, 0xe4, 0xe6, 0xe8, 0xea, 0xec, 0xee, 0xf0, 0xf2, 0xf4, 0xf6, 0xf8, 0xfa, 0xfc, 0xfe,
  60     0x1b, 0x19, 0x1f, 0x1d, 0x13, 0x11, 0x17, 0x15, 0x0b, 0x09, 0x0f, 0x0d, 0x03, 0x01, 0x07, 0x05,
  61     0x3b, 0x39, 0x3f, 0x3d, 0x33, 0x31, 0x37, 0x35, 0x2b, 0x29, 0x2f, 0x2d, 0x23, 0x21, 0x27, 0x25,
  62     0x5b, 0x59, 0x5f, 0x5d, 0x53, 0x51, 0x57, 0x55, 0x4b, 0x49, 0x4f, 0x4d, 0x43, 0x41, 0x47, 0x45,
  63     0x7b, 0x79, 0x7f, 0x7d, 0x73, 0x71, 0x77, 0x75, 0x6b, 0x69, 0x6f, 0x6d, 0x63, 0x61, 0x67, 0x65,
  64     0x9b, 0x99, 0x9f, 0x9d, 0x93, 0x91, 0x97, 0x95, 0x8b, 0x89, 0x8f, 0x8d, 0x83, 0x81, 0x87, 0x85,
  65     0xbb, 0xb9, 0xbf, 0xbd, 0xb3, 0xb1, 0xb7, 0xb5, 0xab, 0xa9, 0xaf, 0xad, 0xa3, 0xa1, 0xa7, 0xa5,
  66     0xdb, 0xd9, 0xdf, 0xdd, 0xd3, 0xd1, 0xd7, 0xd5, 0xcb, 0xc9, 0xcf, 0xcd, 0xc3, 0xc1, 0xc7, 0xc5,
  67     0xfb, 0xf9, 0xff, 0xfd, 0xf3, 0xf1, 0xf7, 0xf5, 0xeb, 0xe9, 0xef, 0xed, 0xe3, 0xe1, 0xe7, 0xe5
  68 };
  69
  70 // ***********************************************************************************
  71 /*
  72    void createXTimeTable(void)
  73    {
  74         uint8_t i = 0;
  75         do {
  76                 xtime[i] = (i << 1) ^ ((i & 0x80) ? BPOLY : 0);
  77         } while (++i != 0);
  78    }
  79  */
  80 // ***********************************************************************************
  81 /*
  82    uint8_t powTable[256];
  83    uint8_t logTable[256];
  84
  85    uint8_t sbox[256];
  86    uint8_t isbox[256];
  87
  88    void createPowLogTables(void)
  89    {
  90         uint8_t i = 0;
  91         uint8_t t = 1;
  92
  93         do {
  94                 powTable[i] = t;
  95                 logTable[t] = i;
  96                 i++;
  97                 t ^= (t << 1) ^ ((t & 0x80) ? BPOLY : 0);
  98         } while (t != 1);
  99
 100         powTable[255] = powTable[0];
 101    }
 102
 103    void createSubstitueBoxTable(void)
 104    {
 105         int i = 0;
 106         do {
 107                 uint8_t temp;
 108
 109                 if (i > 0)
 110                         temp = powTable[255 - logTable[i]];
 111                 else
 112                         temp = 0;
 113
 114                 uint8_t sb = temp ^ 0x63;
 115                 for (int j = 0; j < 4; j++)
 116                 {
 117                         temp = (temp << 1) | (temp >> 7);
 118                         sb ^= temp;
 119                 }
 120
 121                 sbox[i] = sb;
 122         } while (++i != 0);
 123    }
 124
 125    void createInverseSubstitueBoxTable(void)
 126    {
 127         uint8_t i = 0;
 128         uint8_t j = 0;
 129         do {
 130                 do {
 131                         if (sbox[j] == i)
 132                         {
 133                                 isbox[i] = j;
 134                                 j = 255;
 135                         }
 136                 } while (++j != 0);
 137         } while (++i != 0);
 138    }
 139  */
 140 // ***********************************************************************************
 141
 142 void copy_block(void *d, void *s)
 143 {
 144     if (d == s) {
 145         return;
 146     }
 147
 148     register uint8_t *src  = s;
 149     register uint8_t *dest = d;
 150     for (int i = N_BLOCK; i; --i) {
 151         *dest++ = *src++;
 152     }
 153 }
 154
 155 void xor_block(void *d, void *s)
 156 {
 157     register uint8_t *src  = s;
 158     register uint8_t *dest = d;
 159
 160     for (int i = N_BLOCK; i; --i) {
 161         *dest++ ^= *src++;
 162     }
 163 }
 164
 165 void xor_word(uint8_t *d, uint8_t *s)
 166 {
 167     *d++ ^= *s++;
 168     *d++ ^= *s++;
 169     *d++ ^= *s++;
 170     *d++ ^= *s++;
 171 }
 172
 173 void xor_sub_word(uint8_t *d, uint8_t *s)
 174 {
 175     *d++ ^= sbox[*s++];
 176     *d++ ^= sbox[*s++];
 177     *d++ ^= sbox[*s++];
 178     *d++ ^= sbox[*s++];
 179 }
 180
 181 void xor_sub_rot_word(uint8_t *d, uint8_t *s, uint8_t rc)
 182 {
 183     *d++ ^= sbox[s[1]] ^ rc;
 184     *d++ ^= sbox[s[2]];
 185     *d++ ^= sbox[s[3]];
 186     *d++ ^= sbox[s[0]];
 187 }
 188
 189 void mix_sub_column(uint8_t *a)
 190 {
 191     uint8_t a0  = a[0];
 192     uint8_t a1  = a[1];
 193     uint8_t a2  = a[2];
 194     uint8_t a3  = a[3];
 195     uint8_t tmp = a0 ^ a1 ^ a2 ^ a3;
 196
 197     a[0] = a0 ^ xtime[a0 ^ a1] ^ tmp;
 198     a[1] = a1 ^ xtime[a1 ^ a2] ^ tmp;
 199     a[2] = a2 ^ xtime[a2 ^ a3] ^ tmp;
 200     a[3] = a3 ^ xtime[a3 ^ a0] ^ tmp;
 201 }
 202
 203 void mix_sub_columns(void *a)
 204 {
 205     mix_sub_column((uint8_t *)a + 0);
 206     mix_sub_column((uint8_t *)a + 4);
 207     mix_sub_column((uint8_t *)a + 8);
 208     mix_sub_column((uint8_t *)a + 12);
 209 }
 210
 211 void inv_mix_sub_column(uint8_t *a)
 212 {
 213     uint8_t tmp;
 214
 215     tmp   = xtime[xtime[a[0] ^ a[2]]];
 216     a[0] ^= tmp;
 217     a[2] ^= tmp;
 218     tmp   = xtime[xtime[a[1] ^ a[3]]];
 219     a[1] ^= tmp;
 220     a[3] ^= tmp;
 221 }
 222
 223 void inv_mix_sub_columns(void *a)
 224 {
 225     inv_mix_sub_column((uint8_t *)a + 0);
 226     inv_mix_sub_column((uint8_t *)a + 4);
 227     inv_mix_sub_column((uint8_t *)a + 8);
 228     inv_mix_sub_column((uint8_t *)a + 12);
 229
 230     mix_sub_columns(a);
 231 }
 232
 233 void shift_sub_rows(uint8_t *a)
 234 {
 235     uint8_t tmp;
 236
 237     a[0]  = sbox[a[0]];
 238     a[4]  = sbox[a[4]];
 239     a[8]  = sbox[a[8]];
 240     a[12] = sbox[a[12]];
 241
 242     tmp   = a[1];
 243     a[1]  = sbox[a[5]];
 244     a[5]  = sbox[a[9]];
 245     a[9]  = sbox[a[13]];
 246     a[13] = sbox[tmp];
 247
 248     tmp   = a[2];
 249     a[2]  = sbox[a[10]];
 250     a[10] = sbox[tmp];
 251     tmp   = a[6];
 252     a[6]  = sbox[a[14]];
 253     a[14] = sbox[tmp];
 254
 255     tmp   = a[15];
 256     a[15] = sbox[a[11]];
 257     a[11] = sbox[a[7]];
 258     a[7]  = sbox[a[3]];
 259     a[3]  = sbox[tmp];
 260 }
 261
 262 void inv_shift_sub_rows(uint8_t *a)
 263 {
 264     uint8_t tmp;
 265
 266     a[0]  = isbox[a[0]];
 267     a[4]  = isbox[a[4]];
 268     a[8]  = isbox[a[8]];
 269     a[12] = isbox[a[12]];
 270
 271     tmp   = a[13];
 272     a[13] = isbox[a[9]];
 273     a[9]  = isbox[a[5]];
 274     a[5]  = isbox[a[1]];
 275     a[1]  = isbox[tmp];
 276
 277     tmp   = a[2];
 278     a[2]  = isbox[a[10]];
 279     a[10] = isbox[tmp];
 280     tmp   = a[6];
 281     a[6]  = isbox[a[14]];
 282     a[14] = isbox[tmp];
 283
 284     tmp   = a[3];
 285     a[3]  = isbox[a[7]];
 286     a[7]  = isbox[a[11]];
 287     a[11] = isbox[a[15]];
 288     a[15] = isbox[tmp];
 289 }
 290
 291 // ***********************************************************************************
 292
 293 // 'on the fly' encryption key update for 128 bit keys
 294 void update_encrypt_key_128(uint8_t *k, uint8_t *rc)
 295 {
 296     xor_sub_rot_word(k + 0, k + 12, *rc);
 297
 298     *rc = (*rc << 1) ^ ((*rc & 0x80) ? BPOLY : 0);
 299
 300     for (int i = 4; i < 16; i += 4) {
 301         xor_word(k + i + 0, k + i - 4);
 302     }
 303 }
 304
 305 // Encrypt a single block of 16 bytes
 306 void aes_encrypt_cbc_128(void *data, void *key, void *chain_block)
 307 {
 308     uint8_t rc = 1;
 309
 310     if (chain_block) {
 311         xor_block(data, chain_block);
 312     }
 313
 314     for (int round = 10; round; --round) {
 315         xor_block(data, key); // add_round_key
 316         update_encrypt_key_128((uint8_t *)key, &rc);
 317         shift_sub_rows(data);
 318         if (round <= 1) {
 319             continue;
 320         }
 321         mix_sub_columns(data);
 322     }
 323     xor_block(data, key); // add_round_key
 324
 325     if (chain_block) {
 326         copy_block(chain_block, data);
 327     }
 328 }
 329
 330 // 'on the fly' decryption key update for 128 bit keys
 331 void update_decrypt_key_128(uint8_t *k, uint8_t *rc)
 332 {
 333     for (int i = 12; i; i -= 4) {
 334         xor_word(k + i + 0, k + i - 4);
 335     }
 336
 337     *rc = (*rc >> 1) ^ ((*rc & 1) ? DPOLY : 0);
 338
 339     xor_sub_rot_word(k + 0, k + 12, *rc);
 340 }
 341
 342 // Decrypt a single block of 16 bytes
 343 void aes_decrypt_cbc_128(void *data, void *key, void *chain_block)
 344 {
 345     uint8_t tmp_data[N_BLOCK];
 346
 347     uint8_t rc = 0x6c;
 348
 349     copy_block(tmp_data, data);
 350
 351     xor_block(data, key); // add_round_key
 352     for (int round = 10; round; --round) {
 353         inv_shift_sub_rows(data);
 354         update_decrypt_key_128(key, &rc);
 355         xor_block(data, key); // add_round_key
 356         if (round <= 1) {
 357             continue;
 358         }
 359         inv_mix_sub_columns(data);
 360     }
 361
 362     if (chain_block) {
 363         xor_block(data, chain_block);
 364         copy_block(chain_block, tmp_data);
 365     }
 366 }
 367
 368 void aes_decrypt_key_128_create(void *enc_key, void *dec_key)
 369 {
 370     copy_block(dec_key, enc_key);
 371
 372     uint8_t rc = 1;
 373     for (int i = 0; i < 10; i++) {
 374         update_encrypt_key_128(dec_key, &rc);
 375     }
 376 }
 377
 378 // ***********************************************************************************
 379
 380 // 'on the fly' encryption key update for 256 bit keys
 381 void update_encrypt_key_256(uint8_t *k, uint8_t *rc)
 382 {
 383     xor_sub_rot_word(k + 0, k + 28, *rc);
 384
 385     *rc = (*rc << 1) ^ ((*rc & 0x80) ? BPOLY : 0);
 386
 387     for (int i = 4; i < 16; i += 4) {
 388         xor_word(k + i + 0, k + i - 4);
 389     }
 390
 391     xor_sub_word(k + 16, k + 12);
 392
 393     for (int i = 20; i < 32; i += 4) {
 394         xor_word(k + i + 0, k + i - 4);
 395     }
 396 }
 397
 398 // Encrypt a single block of 16 bytes
 399 void aes_encrypt_cbc_256(void *data, void *key, void *chain_block)
 400 {
 401     uint8_t rc = 1;
 402
 403     if (chain_block) {
 404         xor_block(data, chain_block);
 405     }
 406
 407     for (int round = 7; round; --round) {
 408 // printf("key - ");
 409 // uint8_t *p = key;
 410 // for (int i = 0; i < 32; i++) printf("%0.2X ", *p++);
 411 // printf("\r\n");
 412
 413         xor_block(data, key); // add_round_key
 414         shift_sub_rows(data);
 415         mix_sub_columns(data);
 416         xor_block(data, (uint8_t *)key + 16); // add_round_key
 417         update_encrypt_key_256(key, &rc);
 418         shift_sub_rows(data);
 419         if (round <= 1) {
 420             continue;
 421         }
 422         mix_sub_columns(data);
 423     }
 424     xor_block(data, key); // add_round_key
 425
 426     if (chain_block) {
 427         copy_block(chain_block, data);
 428     }
 429 }
 430
 431 // 'on the fly' decryption key update for 256 bit keys
 432 void update_decrypt_key_256(uint8_t *k, uint8_t *rc)
 433 {
 434     for (int i = 28; i >= 20; i -= 4) {
 435         xor_word(k + i + 0, k + i - 4);
 436     }
 437
 438     xor_sub_word(k + 16, k + 12);
 439
 440     for (int i = 12; i; i -= 4) {
 441         xor_word(k + i + 0, k + i - 4);
 442     }
 443
 444     *rc = (*rc >> 1) ^ ((*rc & 1) ? DPOLY : 0);
 445
 446     xor_sub_rot_word(k + 0, k + 28, *rc);
 447 }
 448
 449 // Decrypt a single block of 16 bytes
 450 void aes_decrypt_cbc_256(void *data, void *key, void *chain_block)
 451 {
 452     uint8_t tmp_data[N_BLOCK];
 453
 454     uint8_t rc = 0x80;
 455
 456     copy_block(tmp_data, data);
 457
 458     xor_block(data, key); // add_round_key
 459     for (int round = 7; round; --round) {
 460         inv_shift_sub_rows(data);
 461         update_decrypt_key_256(key, &rc);
 462         xor_block(data, (uint8_t *)key + 16); // add_round_key
 463         inv_mix_sub_columns(data);
 464         inv_shift_sub_rows(data);
 465         xor_block(data, key); // add_round_key
 466         if (round <= 1) {
 467             continue;
 468         }
 469         inv_mix_sub_columns(data);
 470     }
 471
 472     if (chain_block) {
 473         xor_block(data, chain_block);
 474         copy_block(chain_block, tmp_data);
 475     }
 476 }
 477
 478 void aes_decrypt_key_256_create(void *enc_key, void *dec_key)
 479 {
 480     if (dec_key != enc_key) {
 481         copy_block(dec_key, enc_key);
 482         copy_block((uint8_t *)dec_key + 16, (uint8_t *)enc_key + 16);
 483     }
 484
 485     uint8_t rc = 1;
 486     for (int i = 7; i; --i) {
 487         update_encrypt_key_256(dec_key, &rc);
 488     }
 489 }
 490
 491 // ***********************************************************************************