cvs.zerfleddert.de Git - proxmark3-svn/blob - armsrc/desfire_crypto.c

   1 /*-
   2  * Copyright (C) 2010, Romain Tartiere.
   3  *
   4  * This program is free software: you can redistribute it and/or modify it
   5  * under the terms of the GNU Lesser General Public License as published by the
   6  * Free Software Foundation, either version 3 of the License, or (at your
   7  * option) any later version.
   8  *
   9  * This program is distributed in the hope that it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
  12  * more details.
  13  *
  14  * You should have received a copy of the GNU Lesser General Public License
  15  * along with this program.  If not, see <http://www.gnu.org/licenses/>
  16  *
  17  * $Id$
  18  */
  19
  20 /*
  21  * This implementation was written based on information provided by the
  22  * following documents:
  23  *
  24  * NIST Special Publication 800-38B
  25  * Recommendation for Block Cipher Modes of Operation: The CMAC Mode for Authentication
  26  * May 2005
  27  */
  28 #include "desfire_crypto.h"
  29
  30 static void xor (const uint8_t *ivect, uint8_t *data, const size_t len);
  31 static size_t key_macing_length (desfirekey_t key);
  32
  33 static void xor (const uint8_t *ivect, uint8_t *data, const size_t len) {
  34     for (size_t i = 0; i < len; i++) {
  35         data[i] ^= ivect[i];
  36     }
  37 }
  38
  39 void cmac_generate_subkeys ( desfirekey_t key) {
  40     int kbs = key_block_size (key);
  41     const uint8_t R = (kbs == 8) ? 0x1B : 0x87;
  42
  43     uint8_t l[kbs];
  44     memset (l, 0, kbs);
  45
  46     uint8_t ivect[kbs];
  47     memset (ivect, 0, kbs);
  48
  49     mifare_cypher_blocks_chained (NULL, key, ivect, l, kbs, MCD_RECEIVE, MCO_ENCYPHER);
  50
  51     bool xor = false;
  52
  53     // Used to compute CMAC on complete blocks
  54     memcpy (key->cmac_sk1, l, kbs);
  55     xor = l[0] & 0x80;
  56     lsl (key->cmac_sk1, kbs);
  57     if (xor)
  58         key->cmac_sk1[kbs-1] ^= R;
  59
  60     // Used to compute CMAC on the last block if non-complete
  61     memcpy (key->cmac_sk2, key->cmac_sk1, kbs);
  62     xor = key->cmac_sk1[0] & 0x80;
  63     lsl (key->cmac_sk2, kbs);
  64     if (xor)
  65         key->cmac_sk2[kbs-1] ^= R;
  66 }
  67
  68 void cmac (const desfirekey_t key, uint8_t *ivect, const uint8_t *data, size_t len, uint8_t *cmac) {
  69     int kbs = key_block_size (key);
  70     uint8_t *buffer = malloc (padded_data_length (len, kbs));
  71
  72     memcpy (buffer, data, len);
  73
  74     if ((!len) || (len % kbs)) {
  75         buffer[len++] = 0x80;
  76         while (len % kbs) {
  77             buffer[len++] = 0x00;
  78         }
  79         xor (key->cmac_sk2, buffer + len - kbs, kbs);
  80     } else {
  81         xor (key->cmac_sk1, buffer + len - kbs, kbs);
  82     }
  83
  84     mifare_cypher_blocks_chained (NULL, key, ivect, buffer, len, MCD_SEND, MCO_ENCYPHER);
  85
  86     memcpy (cmac, ivect, kbs);
  87         free(buffer);
  88 }
  89
  90 size_t key_block_size (const desfirekey_t key) {
  91     size_t block_size = 8;
  92
  93     switch (key->type) {
  94                 case T_DES:
  95                 case T_3DES:
  96                 case T_3K3DES:
  97                         block_size = 8;
  98                         break;
  99                 case T_AES:
 100                         block_size = 16;
 101                         break;
 102     }
 103
 104     return block_size;
 105 }
 106
 107 /*
 108  * Size of MACing produced with the key.
 109  */
 110 static size_t key_macing_length (const desfirekey_t key) {
 111     size_t mac_length = MAC_LENGTH;
 112
 113     switch (key->type) {
 114     case T_DES:
 115     case T_3DES:
 116         mac_length = MAC_LENGTH;
 117         break;
 118     case T_3K3DES:
 119     case T_AES:
 120         mac_length = CMAC_LENGTH;
 121         break;
 122     }
 123
 124     return mac_length;
 125 }
 126
 127 /*
 128  * Size required to store nbytes of data in a buffer of size n*block_size.
 129  */
 130 size_t padded_data_length (const size_t nbytes, const size_t block_size) {
 131     if ((!nbytes) || (nbytes % block_size))
 132         return ((nbytes / block_size) + 1) * block_size;
 133     else
 134         return nbytes;
 135 }
 136
 137 /*
 138  * Buffer size required to MAC nbytes of data
 139  */
 140 size_t maced_data_length (const desfirekey_t key, const size_t nbytes) {
 141     return nbytes + key_macing_length (key);
 142 }
 143 /*
 144  * Buffer size required to encipher nbytes of data and a two bytes CRC.
 145  */
 146 size_t enciphered_data_length (const desfiretag_t tag, const size_t nbytes, int communication_settings) {
 147     size_t crc_length = 0;
 148     if (!(communication_settings & NO_CRC)) {
 149         switch (DESFIRE(tag)->authentication_scheme) {
 150         case AS_LEGACY:
 151             crc_length = 2;
 152             break;
 153         case AS_NEW:
 154             crc_length = 4;
 155             break;
 156         }
 157     }
 158
 159     size_t block_size = DESFIRE(tag)->session_key ? key_block_size (DESFIRE(tag)->session_key) : 1;
 160
 161     return padded_data_length (nbytes + crc_length, block_size);
 162 }
 163
 164 void* mifare_cryto_preprocess_data (desfiretag_t tag, void *data, size_t *nbytes, size_t offset, int communication_settings) {
 165     uint8_t *res = data;
 166     uint8_t mac[4];
 167     size_t edl;
 168     bool append_mac = true;
 169     desfirekey_t key = DESFIRE(tag)->session_key;
 170
 171     if (!key)
 172         return data;
 173
 174     switch (communication_settings & MDCM_MASK) {
 175     case MDCM_PLAIN:
 176         if (AS_LEGACY == DESFIRE(tag)->authentication_scheme)
 177             break;
 178
 179         /*
 180          * When using new authentication methods, PLAIN data transmission from
 181          * the PICC to the PCD are CMACed, so we have to maintain the
 182          * cryptographic initialisation vector up-to-date to check data
 183          * integrity later.
 184          *
 185          * The only difference with CMACed data transmission is that the CMAC
 186          * is not apended to the data send by the PCD to the PICC.
 187          */
 188
 189         append_mac = false;
 190
 191         /* pass through */
 192     case MDCM_MACED:
 193         switch (DESFIRE(tag)->authentication_scheme) {
 194         case AS_LEGACY:
 195             if (!(communication_settings & MAC_COMMAND))
 196                 break;
 197
 198             /* pass through */
 199             edl = padded_data_length (*nbytes - offset, key_block_size (DESFIRE(tag)->session_key)) + offset;
 200
 201             // Fill in the crypto buffer with data ...
 202             memcpy (res, data, *nbytes);
 203             // ... and 0 padding
 204             memset (res + *nbytes, 0, edl - *nbytes);
 205
 206             mifare_cypher_blocks_chained (tag, NULL, NULL, res + offset, edl - offset, MCD_SEND, MCO_ENCYPHER);
 207
 208             memcpy (mac, res + edl - 8, 4);
 209
 210             // Copy again provided data (was overwritten by mifare_cypher_blocks_chained)
 211             memcpy (res, data, *nbytes);
 212
 213             if (!(communication_settings & MAC_COMMAND))
 214                 break;
 215             // Append MAC
 216             size_t bla = maced_data_length (DESFIRE(tag)->session_key, *nbytes - offset) + offset;
 217                         bla++;
 218
 219             memcpy (res + *nbytes, mac, 4);
 220
 221             *nbytes += 4;
 222             break;
 223         case AS_NEW:
 224             if (!(communication_settings & CMAC_COMMAND))
 225                 break;
 226             cmac (key, DESFIRE (tag)->ivect, res, *nbytes, DESFIRE (tag)->cmac);
 227
 228             if (append_mac) {
 229                 size_t len = maced_data_length (key, *nbytes);
 230                                 ++len;
 231                 memcpy (res, data, *nbytes);
 232                 memcpy (res + *nbytes, DESFIRE (tag)->cmac, CMAC_LENGTH);
 233                 *nbytes += CMAC_LENGTH;
 234             }
 235             break;
 236         }
 237
 238         break;
 239     case MDCM_ENCIPHERED:
 240         /*  |<-------------- data -------------->|
 241          *  |<--- offset -->|                    |
 242          *  +---------------+--------------------+-----+---------+
 243          *  | CMD + HEADERS | DATA TO BE SECURED | CRC | PADDING |
 244          *  +---------------+--------------------+-----+---------+ ----------------
 245          *  |               |<~~~~v~~~~~~~~~~~~~>|  ^  |         |   (DES / 3DES)
 246          *  |               |     `---- crc16() ----'  |         |
 247          *  |               |                    |  ^  |         | ----- *or* -----
 248          *  |<~~~~~~~~~~~~~~~~~~~~v~~~~~~~~~~~~~>|  ^  |         |  (3K3DES / AES)
 249          *                  |     `---- crc32() ----'  |         |
 250          *                  |                                    | ---- *then* ----
 251          *                  |<---------------------------------->|
 252          *                            encypher()/decypher()
 253          */
 254
 255             if (!(communication_settings & ENC_COMMAND))
 256                 break;
 257             edl = enciphered_data_length (tag, *nbytes - offset, communication_settings) + offset;
 258
 259             // Fill in the crypto buffer with data ...
 260             memcpy (res, data, *nbytes);
 261             if (!(communication_settings & NO_CRC)) {
 262                 // ... CRC ...
 263                 switch (DESFIRE (tag)->authentication_scheme) {
 264                 case AS_LEGACY:
 265                     AppendCrc14443a(res + offset, *nbytes - offset);
 266                     *nbytes += 2;
 267                     break;
 268                 case AS_NEW:
 269                     crc32_append (res, *nbytes);
 270                     *nbytes += 4;
 271                     break;
 272                 }
 273             }
 274             // ... and padding
 275             memset (res + *nbytes, 0, edl - *nbytes);
 276
 277             *nbytes = edl;
 278
 279             mifare_cypher_blocks_chained (tag, NULL, NULL, res + offset, *nbytes - offset, MCD_SEND, (AS_NEW == DESFIRE(tag)->authentication_scheme) ? MCO_ENCYPHER : MCO_DECYPHER);
 280         break;
 281     default:
 282
 283         *nbytes = -1;
 284         res = NULL;
 285         break;
 286     }
 287
 288     return res;
 289
 290 }
 291
 292 void* mifare_cryto_postprocess_data (desfiretag_t tag, void *data, size_t *nbytes, int communication_settings)
 293 {
 294     void *res = data;
 295     size_t edl;
 296     void *edata = NULL;
 297     uint8_t first_cmac_byte = 0x00;
 298
 299     desfirekey_t key = DESFIRE(tag)->session_key;
 300
 301     if (!key)
 302         return data;
 303
 304     // Return directly if we just have a status code.
 305     if (1 == *nbytes)
 306         return res;
 307
 308     switch (communication_settings & MDCM_MASK) {
 309     case MDCM_PLAIN:
 310
 311         if (AS_LEGACY == DESFIRE(tag)->authentication_scheme)
 312             break;
 313
 314         /* pass through */
 315     case MDCM_MACED:
 316         switch (DESFIRE (tag)->authentication_scheme) {
 317         case AS_LEGACY:
 318             if (communication_settings & MAC_VERIFY) {
 319                 *nbytes -= key_macing_length (key);
 320                 if (*nbytes <= 0) {
 321                     *nbytes = -1;
 322                     res = NULL;
 323 #ifdef WITH_DEBUG
 324                     Dbprintf ("No room for MAC!");
 325 #endif
 326                     break;
 327                 }
 328
 329                 edl = enciphered_data_length (tag, *nbytes - 1, communication_settings);
 330                 edata = malloc (edl);
 331
 332                 memcpy (edata, data, *nbytes - 1);
 333                 memset ((uint8_t *)edata + *nbytes - 1, 0, edl - *nbytes + 1);
 334
 335                 mifare_cypher_blocks_chained (tag, NULL, NULL, edata, edl, MCD_SEND, MCO_ENCYPHER);
 336
 337                 if (0 != memcmp ((uint8_t *)data + *nbytes - 1, (uint8_t *)edata + edl - 8, 4)) {
 338 #ifdef WITH_DEBUG
 339                     Dbprintf ("MACing not verified");
 340                     hexdump ((uint8_t *)data + *nbytes - 1, key_macing_length (key), "Expect ", 0);
 341                     hexdump ((uint8_t *)edata + edl - 8, key_macing_length (key), "Actual ", 0);
 342 #endif
 343                     DESFIRE (tag)->last_pcd_error = CRYPTO_ERROR;
 344                     *nbytes = -1;
 345                     res = NULL;
 346                 }
 347             }
 348             break;
 349         case AS_NEW:
 350             if (!(communication_settings & CMAC_COMMAND))
 351                 break;
 352             if (communication_settings & CMAC_VERIFY) {
 353                 if (*nbytes < 9) {
 354                     *nbytes = -1;
 355                     res = NULL;
 356                     break;
 357                 }
 358                 first_cmac_byte = ((uint8_t *)data)[*nbytes - 9];
 359                 ((uint8_t *)data)[*nbytes - 9] = ((uint8_t *)data)[*nbytes-1];
 360             }
 361
 362             int n = (communication_settings & CMAC_VERIFY) ? 8 : 0;
 363             cmac (key, DESFIRE (tag)->ivect, ((uint8_t *)data), *nbytes - n, DESFIRE (tag)->cmac);
 364
 365             if (communication_settings & CMAC_VERIFY) {
 366                 ((uint8_t *)data)[*nbytes - 9] = first_cmac_byte;
 367                 if (0 != memcmp (DESFIRE (tag)->cmac, (uint8_t *)data + *nbytes - 9, 8)) {
 368 #ifdef WITH_DEBUG
 369                     Dbprintf ("CMAC NOT verified :-(");
 370                     hexdump ((uint8_t *)data + *nbytes - 9, 8, "Expect ", 0);
 371                     hexdump (DESFIRE (tag)->cmac, 8, "Actual ", 0);
 372 #endif
 373                     DESFIRE (tag)->last_pcd_error = CRYPTO_ERROR;
 374                     *nbytes = -1;
 375                     res = NULL;
 376                 } else {
 377                     *nbytes -= 8;
 378                 }
 379             }
 380             break;
 381         }
 382
 383         free (edata);
 384
 385         break;
 386     case MDCM_ENCIPHERED:
 387         (*nbytes)--;
 388         bool verified = false;
 389         int crc_pos = 0x00;
 390         int end_crc_pos = 0x00;
 391         uint8_t x;
 392
 393         /*
 394          * AS_LEGACY:
 395          * ,-----------------+-------------------------------+--------+
 396          * \     BLOCK n-1   |              BLOCK n          | STATUS |
 397          * /  PAYLOAD | CRC0 | CRC1 | 0x80? | 0x000000000000 | 0x9100 |
 398          * `-----------------+-------------------------------+--------+
 399          *
 400          *         <------------ DATA ------------>
 401          * FRAME = PAYLOAD + CRC(PAYLOAD) + PADDING
 402          *
 403          * AS_NEW:
 404          * ,-------------------------------+-----------------------------------------------+--------+
 405          * \                 BLOCK n-1     |                  BLOCK n                      | STATUS |
 406          * /  PAYLOAD | CRC0 | CRC1 | CRC2 | CRC3 | 0x80? | 0x0000000000000000000000000000 | 0x9100 |
 407          * `-------------------------------+-----------------------------------------------+--------+
 408          * <----------------------------------- DATA ------------------------------------->|
 409          *
 410          *         <----------------- DATA ---------------->
 411          * FRAME = PAYLOAD + CRC(PAYLOAD + STATUS) + PADDING + STATUS
 412          *                                    `------------------'
 413          */
 414
 415         mifare_cypher_blocks_chained (tag, NULL, NULL, res, *nbytes, MCD_RECEIVE, MCO_DECYPHER);
 416
 417         /*
 418          * Look for the CRC and ensure it is followed by NULL padding.  We
 419          * can't start by the end because the CRC is supposed to be 0 when
 420          * verified, and accumulating 0's in it should not change it.
 421          */
 422         switch (DESFIRE (tag)->authentication_scheme) {
 423         case AS_LEGACY:
 424             crc_pos = *nbytes - 8 - 1; // The CRC can be over two blocks
 425             if (crc_pos < 0) {
 426                 /* Single block */
 427                 crc_pos = 0;
 428             }
 429             break;
 430         case AS_NEW:
 431             /* Move status between payload and CRC */
 432             res = DESFIRE (tag)->crypto_buffer;
 433             memcpy (res, data, *nbytes);
 434
 435             crc_pos = (*nbytes) - 16 - 3;
 436             if (crc_pos < 0) {
 437                 /* Single block */
 438                 crc_pos = 0;
 439             }
 440             memcpy ((uint8_t *)res + crc_pos + 1, (uint8_t *)res + crc_pos, *nbytes - crc_pos);
 441             ((uint8_t *)res)[crc_pos] = 0x00;
 442             crc_pos++;
 443             *nbytes += 1;
 444             break;
 445         }
 446
 447         do {
 448             uint16_t crc16 =0x00;
 449             uint32_t crc;
 450             switch (DESFIRE (tag)->authentication_scheme) {
 451             case AS_LEGACY:
 452                 end_crc_pos = crc_pos + 2;
 453                 AppendCrc14443a (res, end_crc_pos);
 454
 455                                 //
 456
 457
 458                 crc = crc16;
 459                 break;
 460             case AS_NEW:
 461                 end_crc_pos = crc_pos + 4;
 462                 crc32 (res, end_crc_pos, (uint8_t *)&crc);
 463                 break;
 464             }
 465             if (!crc) {
 466                 verified = true;
 467                 for (int n = end_crc_pos; n < *nbytes - 1; n++) {
 468                     uint8_t byte = ((uint8_t *)res)[n];
 469                     if (!( (0x00 == byte) || ((0x80 == byte) && (n == end_crc_pos)) ))
 470                         verified = false;
 471                 }
 472             }
 473             if (verified) {
 474                 *nbytes = crc_pos;
 475                 switch (DESFIRE (tag)->authentication_scheme) {
 476                 case AS_LEGACY:
 477                     ((uint8_t *)data)[(*nbytes)++] = 0x00;
 478                     break;
 479                 case AS_NEW:
 480                     /* The status byte was already before the CRC */
 481                     break;
 482                 }
 483             } else {
 484                 switch (DESFIRE (tag)->authentication_scheme) {
 485                 case AS_LEGACY:
 486                     break;
 487                 case AS_NEW:
 488                     x = ((uint8_t *)res)[crc_pos - 1];
 489                     ((uint8_t *)res)[crc_pos - 1] = ((uint8_t *)res)[crc_pos];
 490                     ((uint8_t *)res)[crc_pos] = x;
 491                     break;
 492                 }
 493                 crc_pos++;
 494             }
 495         } while (!verified && (end_crc_pos < *nbytes));
 496
 497         if (!verified) {
 498 #ifdef WITH_DEBUG
 499             /* FIXME In some configurations, the file is transmitted PLAIN */
 500             Dbprintf("CRC not verified in decyphered stream");
 501 #endif
 502             DESFIRE (tag)->last_pcd_error = CRYPTO_ERROR;
 503             *nbytes = -1;
 504             res = NULL;
 505         }
 506
 507         break;
 508     default:
 509         Dbprintf("Unknown communication settings");
 510         *nbytes = -1;
 511         res = NULL;
 512         break;
 513
 514     }
 515     return res;
 516 }
 517
 518
 519 void mifare_cypher_single_block (desfirekey_t key, uint8_t *data, uint8_t *ivect, MifareCryptoDirection direction, MifareCryptoOperation operation, size_t block_size)
 520 {
 521     uint8_t ovect[MAX_CRYPTO_BLOCK_SIZE];
 522
 523     if (direction == MCD_SEND) {
 524         xor (ivect, data, block_size);
 525     } else {
 526         memcpy (ovect, data, block_size);
 527     }
 528
 529     uint8_t edata[MAX_CRYPTO_BLOCK_SIZE];
 530
 531     switch (key->type) {
 532     case T_DES:
 533         switch (operation) {
 534         case MCO_ENCYPHER:
 535             //DES_ecb_encrypt ((DES_cblock *) data, (DES_cblock *) edata, &(key->ks1), DES_ENCRYPT);
 536                         des_enc(edata, data, key->data);
 537             break;
 538         case MCO_DECYPHER:
 539             //DES_ecb_encrypt ((DES_cblock *) data, (DES_cblock *) edata, &(key->ks1), DES_DECRYPT);
 540                         des_dec(edata, data, key->data);
 541             break;
 542         }
 543         break;
 544     case T_3DES:
 545         switch (operation) {
 546         case MCO_ENCYPHER:
 547             // DES_ecb_encrypt ((DES_cblock *) data,  (DES_cblock *) edata, &(key->ks1), DES_ENCRYPT);
 548             // DES_ecb_encrypt ((DES_cblock *) edata, (DES_cblock *) data,  &(key->ks2), DES_DECRYPT);
 549             // DES_ecb_encrypt ((DES_cblock *) data,  (DES_cblock *) edata, &(key->ks1), DES_ENCRYPT);
 550                         tdes_enc(edata,data, key->data);
 551             break;
 552         case MCO_DECYPHER:
 553             // DES_ecb_encrypt ((DES_cblock *) data,  (DES_cblock *) edata, &(key->ks1), DES_DECRYPT);
 554             // DES_ecb_encrypt ((DES_cblock *) edata, (DES_cblock *) data,  &(key->ks2), DES_ENCRYPT);
 555             // DES_ecb_encrypt ((DES_cblock *) data,  (DES_cblock *) edata, &(key->ks1), DES_DECRYPT);
 556                         tdes_dec(data, edata, key->data);
 557             break;
 558         }
 559         break;
 560     case T_3K3DES:
 561         switch (operation) {
 562         case MCO_ENCYPHER:
 563                         tdes_enc(edata,data, key->data);
 564             // DES_ecb_encrypt ((DES_cblock *) data,  (DES_cblock *) edata, &(key->ks1), DES_ENCRYPT);
 565             // DES_ecb_encrypt ((DES_cblock *) edata, (DES_cblock *) data,  &(key->ks2), DES_DECRYPT);
 566             // DES_ecb_encrypt ((DES_cblock *) data,  (DES_cblock *) edata, &(key->ks3), DES_ENCRYPT);
 567             break;
 568         case MCO_DECYPHER:
 569                         tdes_dec(data, edata, key->data);
 570                         // DES_ecb_encrypt ((DES_cblock *) data,  (DES_cblock *) edata, &(key->ks3), DES_DECRYPT);
 571             // DES_ecb_encrypt ((DES_cblock *) edata, (DES_cblock *) data,  &(key->ks2), DES_ENCRYPT);
 572             // DES_ecb_encrypt ((DES_cblock *) data,  (DES_cblock *) edata, &(key->ks1), DES_DECRYPT);
 573             break;
 574         }
 575         break;
 576     case T_AES:
 577         switch (operation)
 578                 {
 579                         case MCO_ENCYPHER:
 580                         {
 581                                 AesCtx ctx;
 582                                 AesCtxIni(&ctx, ivect, key->data, KEY128,CBC);
 583                                 AesEncrypt(&ctx, data, edata, sizeof(edata) );
 584                                 break;
 585                         }
 586                         case MCO_DECYPHER:
 587                         {
 588                                 AesCtx ctx;
 589                                 AesCtxIni(&ctx, ivect, key->data, KEY128,CBC);
 590                                 AesDecrypt(&ctx, edata, data, sizeof(edata));
 591                                 break;
 592                         }
 593         }
 594         break;
 595     }
 596
 597     memcpy (data, edata, block_size);
 598
 599     if (direction == MCD_SEND) {
 600         memcpy (ivect, data, block_size);
 601     } else {
 602         xor (ivect, data, block_size);
 603         memcpy (ivect, ovect, block_size);
 604     }
 605 }
 606
 607 /*
 608  * This function performs all CBC cyphering / deciphering.
 609  *
 610  * The tag argument may be NULL, in which case both key and ivect shall be set.
 611  * When using the tag session_key and ivect for processing data, these
 612  * arguments should be set to NULL.
 613  *
 614  * Because the tag may contain additional data, one may need to call this
 615  * function with tag, key and ivect defined.
 616  */
 617 void mifare_cypher_blocks_chained (desfiretag_t tag, desfirekey_t key, uint8_t *ivect, uint8_t *data, size_t data_size, MifareCryptoDirection direction, MifareCryptoOperation operation) {
 618     size_t block_size;
 619
 620     if (tag) {
 621         if (!key)
 622             key = DESFIRE (tag)->session_key;
 623         if (!ivect)
 624             ivect = DESFIRE (tag)->ivect;
 625
 626         switch (DESFIRE (tag)->authentication_scheme) {
 627                         case AS_LEGACY:
 628                                 memset (ivect, 0, MAX_CRYPTO_BLOCK_SIZE);
 629                                 break;
 630                         case AS_NEW:
 631                                 break;
 632         }
 633     }
 634
 635     block_size = key_block_size (key);
 636
 637     size_t offset = 0;
 638     while (offset < data_size) {
 639         mifare_cypher_single_block (key, data + offset, ivect, direction, operation, block_size);
 640         offset += block_size;
 641     }
 642 }