/* 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@iahu.ca, http://libtomcrypt.org */#include "mycrypt.h"/* The Mask Generation Function (MGF1) for PKCS #1 -- Tom St Denis */#ifdef PKCS_1int pkcs_1_mgf1(const unsigned char *seed, unsigned long seedlen,                      int            hash_idx,                      unsigned char *mask, unsigned long masklen){   unsigned long hLen, counter, x;   int           err;   hash_state    md;   unsigned char buf[MAXBLOCKSIZE];    _ARGCHK(seed != NULL);   _ARGCHK(mask != NULL);   /* ensure valid hash */   if ((err = hash_is_valid(hash_idx)) != CRYPT_OK) {       return err;   }   /* get hash output size */   hLen = hash_descriptor[hash_idx].hashsize;   /* start counter */   counter = 0;   while (masklen > 0) {       /* handle counter */       STORE32H(counter, buf);       ++counter;       /* get hash of seed || counter */       hash_descriptor[hash_idx].init(&md);       if ((err = hash_descriptor[hash_idx].process(&md, seed, seedlen)) != CRYPT_OK) {          return err;       }       if ((err = hash_descriptor[hash_idx].process(&md, buf, 4)) != CRYPT_OK) {          return err;       }       if ((err = hash_descriptor[hash_idx].done(&md, buf)) != CRYPT_OK) {          return err;       }       /* store it */       for (x = 0; x < hLen && masklen > 0; x++, masklen--) {          *mask++ = buf[x];       }   }   return CRYPT_OK;}#endif /* PKCS_1 */