/* 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"#ifdef CFBint cfb_decrypt(const unsigned char *ct, unsigned char *pt, unsigned long len, symmetric_CFB *cfb){   int err;   _ARGCHK(pt != NULL);   _ARGCHK(ct != NULL);   _ARGCHK(cfb != NULL);   if ((err = cipher_is_valid(cfb->cipher)) != CRYPT_OK) {       return err;   }   /* is blocklen/padlen valid? */   if (cfb->blocklen < 0 || cfb->blocklen > (int)sizeof(cfb->IV) ||       cfb->padlen   < 0 || cfb->padlen   > (int)sizeof(cfb->pad)) {      return CRYPT_INVALID_ARG;   }   while (len-- > 0) {       if (cfb->padlen == cfb->blocklen) {          cipher_descriptor[cfb->cipher].ecb_encrypt(cfb->pad, cfb->IV, &cfb->key);          cfb->padlen = 0;       }       cfb->pad[cfb->padlen] = *ct;       *pt = *ct ^ cfb->IV[cfb->padlen];       ++pt;        ++ct;       ++cfb->padlen;   }   return CRYPT_OK;}#endif