cbc_encrypt.c

/* LibTomCrypt, modular cryptographic library -- Tom St Denis
 *
 * LibTomCrypt is a library that provides various cryptographic
 * algorithms in a highly modular and flexible manner.
 *
 * The library is free for all purposes without any express
 * guarantee it works.
 */
#include "tomcrypt.h"

/**
   @file cbc_encrypt.c
   CBC implementation, encrypt block, Tom St Denis
*/


#ifdef LTC_CBC_MODE

/**
  CBC encrypt
  @param pt     Plaintext
  @param ct     [out] Ciphertext
  @param len    The number of bytes to process (must be multiple of block length)
  @param cbc    CBC state
  @return CRYPT_OK if successful
*/
int cbc_encrypt(const unsigned char *pt, unsigned char *ct, unsigned long len, symmetric_CBC *cbc)
{
   int x, err;

   LTC_ARGCHK(pt != NULL);
   LTC_ARGCHK(ct != NULL);
   LTC_ARGCHK(cbc != NULL);

   if ((err = cipher_is_valid(cbc->cipher)) != CRYPT_OK) {
       return err;
   }

   /* is blocklen valid? */
   if (cbc->blocklen < 1 || cbc->blocklen > (int)sizeof(cbc->IV)) {
      return CRYPT_INVALID_ARG;
   }

   if (len % cbc->blocklen) {
      return CRYPT_INVALID_ARG;
   }
#ifdef LTC_FAST
   if (cbc->blocklen % sizeof(LTC_FAST_TYPE)) {
      return CRYPT_INVALID_ARG;
   }
#endif

   if (cipher_descriptor[cbc->cipher].accel_cbc_encrypt != NULL) {
      return cipher_descriptor[cbc->cipher].accel_cbc_encrypt(pt, ct, len / cbc->blocklen, cbc->IV, &cbc->key);
   } else {
      while (len) {
         /* xor IV against plaintext */
         #if defined(LTC_FAST)
         for (x = 0; x < cbc->blocklen; x += sizeof(LTC_FAST_TYPE)) {
            *(LTC_FAST_TYPE_PTR_CAST((unsigned char *)cbc->IV + x)) ^= *(LTC_FAST_TYPE_PTR_CAST((unsigned char *)pt + x));
         }
    #else
         for (x = 0; x < cbc->blocklen; x++) {
            cbc->IV[x] ^= pt[x];
         }
    #endif

         /* encrypt */
         if ((err = cipher_descriptor[cbc->cipher].ecb_encrypt(cbc->IV, ct, &cbc->key)) != CRYPT_OK) {
            return err;
         }

         /* store IV [ciphertext] for a future block */
         #if defined(LTC_FAST)
         for (x = 0; x < cbc->blocklen; x += sizeof(LTC_FAST_TYPE)) {
            *(LTC_FAST_TYPE_PTR_CAST((unsigned char *)cbc->IV + x)) = *(LTC_FAST_TYPE_PTR_CAST((unsigned char *)ct + x));
         }
    #else
         for (x = 0; x < cbc->blocklen; x++) {
            cbc->IV[x] = ct[x];
         }
    #endif

         ct  += cbc->blocklen;
         pt  += cbc->blocklen;
         len -= cbc->blocklen;
      }
   }
   return CRYPT_OK;
}

#endif