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      1 /* LibTomCrypt, modular cryptographic library -- Tom St Denis
      2  *
      3  * LibTomCrypt is a library that provides various cryptographic
      4  * algorithms in a highly modular and flexible manner.
      5  *
      6  * The library is free for all purposes without any express
      7  * guarantee it works.
      8  *
      9  * Tom St Denis, tomstdenis (at) gmail.com, http://libtomcrypt.com
     10  */
     11 #include "tomcrypt.h"
     12 
     13 /**
     14   @file xcbc_init.c
     15   XCBC Support, start an XCBC state
     16 */
     17 
     18 #ifdef LTC_XCBC
     19 
     20 /** Initialize XCBC-MAC state
     21   @param xcbc    [out] XCBC state to initialize
     22   @param cipher  Index of cipher to use
     23   @param key     [in]  Secret key
     24   @param keylen  Length of secret key in octets
     25   Return CRYPT_OK on success
     26 */
     27 int xcbc_init(xcbc_state *xcbc, int cipher, const unsigned char *key, unsigned long keylen)
     28 {
     29    int            x, y, err;
     30    symmetric_key *skey;
     31 
     32    LTC_ARGCHK(xcbc != NULL);
     33    LTC_ARGCHK(key  != NULL);
     34 
     35    /* schedule the key */
     36    if ((err = cipher_is_valid(cipher)) != CRYPT_OK) {
     37       return err;
     38    }
     39 
     40 #ifdef LTC_FAST
     41    if (cipher_descriptor[cipher].block_length % sizeof(LTC_FAST_TYPE)) {
     42        return CRYPT_INVALID_ARG;
     43    }
     44 #endif
     45 
     46    /* schedule the user key */
     47    skey = XCALLOC(1, sizeof(*skey));
     48    if (skey == NULL) {
     49       return CRYPT_MEM;
     50    }
     51 
     52    if ((err = cipher_descriptor[cipher].setup(key, keylen, 0, skey)) != CRYPT_OK) {
     53       goto done;
     54    }
     55 
     56    /* make the three keys */
     57    for (y = 0; y < 3; y++) {
     58      for (x = 0; x < cipher_descriptor[cipher].block_length; x++) {
     59         xcbc->K[y][x] = y + 1;
     60      }
     61      cipher_descriptor[cipher].ecb_encrypt(xcbc->K[y], xcbc->K[y], skey);
     62    }
     63 
     64    /* setup K1 */
     65    err = cipher_descriptor[cipher].setup(xcbc->K[0], cipher_descriptor[cipher].block_length, 0, &xcbc->key);
     66 
     67    /* setup struct */
     68    zeromem(xcbc->IV, cipher_descriptor[cipher].block_length);
     69    xcbc->blocksize = cipher_descriptor[cipher].block_length;
     70    xcbc->cipher    = cipher;
     71    xcbc->buflen    = 0;
     72 done:
     73    cipher_descriptor[cipher].done(skey);
     74 #ifdef LTC_CLEAN_STACK
     75    zeromem(skey, sizeof(*skey));
     76 #endif
     77    XFREE(skey);
     78    return err;
     79 }
     80 
     81 #endif
     82 
     83 /* $Source: /cvs/libtom/libtomcrypt/src/mac/xcbc/xcbc_init.c,v $ */
     84 /* $Revision: 1.4 $ */
     85 /* $Date: 2006/11/07 03:23:46 $ */
     86 
     87