Function xcbc_init

extern/libtomcrypt/src/mac/xcbc/xcbc_init.c:25–99

Initialize XCBC-MAC state @param xcbc [out] XCBC state to initialize @param cipher Index of cipher to use @param key [in] Secret key @param keylen Length of secret key in octets Return CRYPT_OK on success */

  Return CRYPT_OK on success
*/
int xcbc_init(xcbc_state *xcbc, int cipher, const unsigned char *key, unsigned long keylen)
{
   int            x, y, err;
   symmetric_key *skey;
   unsigned long  k1;

   LTC_ARGCHK(xcbc != NULL);
   LTC_ARGCHK(key  != NULL);

   /* schedule the key */
   if ((err = cipher_is_valid(cipher)) != CRYPT_OK) {
      return err;
   }

#ifdef LTC_FAST
   if (cipher_descriptor[cipher].block_length % sizeof(LTC_FAST_TYPE)) {
       return CRYPT_INVALID_ARG;
   }
#endif

   skey = NULL;

   /* are we in pure XCBC mode with three keys? */
   if (keylen & LTC_XCBC_PURE) {
      keylen &= ~LTC_XCBC_PURE;

      if (keylen < 2UL*cipher_descriptor[cipher].block_length) {
         return CRYPT_INVALID_ARG;
      }

      k1      = keylen - 2*cipher_descriptor[cipher].block_length;
      XMEMCPY(xcbc->K[0], key, k1);
      XMEMCPY(xcbc->K[1], key+k1, cipher_descriptor[cipher].block_length);
      XMEMCPY(xcbc->K[2], key+k1 + cipher_descriptor[cipher].block_length, cipher_descriptor[cipher].block_length);
   } else {
      /* use the key expansion */
      k1      = cipher_descriptor[cipher].block_length;

      /* schedule the user key */
      skey = XCALLOC(1, sizeof(*skey));
      if (skey == NULL) {
         return CRYPT_MEM;
      }

      if ((err = cipher_descriptor[cipher].setup(key, keylen, 0, skey)) != CRYPT_OK) {
         goto done;
      }

      /* make the three keys */
      for (y = 0; y < 3; y++) {
        for (x = 0; x < cipher_descriptor[cipher].block_length; x++) {
           xcbc->K[y][x] = y + 1;
        }
        cipher_descriptor[cipher].ecb_encrypt(xcbc->K[y], xcbc->K[y], skey);
      }
   }

   /* setup K1 */