/* 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.
 *
 * Tom St Denis, tomstdenis@gmail.com, http://libtom.org
 */
#include "tomcrypt.h"
#include <ncr_int.h>

/** 
  @file pkcs_1_mgf1.c
  The Mask Generation Function (MGF1) for LTC_PKCS #1, Tom St Denis 
*/

#ifdef LTC_PKCS_1

/**
   Perform LTC_PKCS #1 MGF1 (internal)
   @param seed        The seed for MGF1
   @param seedlen     The length of the seed
   @param hash_idx    The index of the hash desired
   @param mask        [out] The destination
   @param masklen     The length of the mask desired
   @return CRYPT_OK if successful
*/
int pkcs_1_mgf1(int                  hash_idx,
                const unsigned char *seed, unsigned long seedlen,
                      unsigned char *mask, unsigned long masklen)
{
   unsigned long hLen, x;
   ulong32       counter;
   int           err;
   unsigned char *buf;
 
   LTC_ARGCHK(seed != NULL);
   LTC_ARGCHK(mask != NULL);

   /* ensure valid hash */
   if ((err = hash_is_valid(hash_idx)) != CRYPT_OK) { 
      return err;
   }

   /* get hash output size */
   hLen = _ncr_algo_digest_size(hash_idx);

   /* allocate memory */
   buf = XMALLOC(hLen);
   if (buf == NULL) {
      return CRYPT_MEM;
   }

   /* start counter */
   counter = 0;

   while (masklen > 0) {
       /* handle counter */
       STORE32H(counter, buf);
       ++counter;

       err = hash_memory_multi(hash_idx, buf, &hLen, seed, seedlen, buf, (unsigned long) 4, NULL, 0);
       if (err != CRYPT_OK) {
          goto LBL_ERR;
       }

       /* store it */
       for (x = 0; x < hLen && masklen > 0; x++, masklen--) {
          *mask++ = buf[x];
       }
   }

   err = CRYPT_OK;
LBL_ERR:
#ifdef LTC_CLEAN_STACK
   zeromem(buf, hLen);
#endif

   XFREE(buf);

   return err;
}

#endif /* LTC_PKCS_1 */

/* $Source: /cvs/libtom/libtomcrypt/src/pk/pkcs1/pkcs_1_mgf1.c,v $ */
/* $Revision: 1.8 $ */
/* $Date: 2007/05/12 14:32:35 $ */