/* 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://libtomcrypt.com *//**   @file ocb_decrypt_verify_memory.c  OCB implementation, helper to decrypt block of memory, by Tom St Denis */#include "tomcrypt.h"#ifdef OCB_MODE/**   Decrypt and compare the tag with OCB.   @param cipher     The index of the cipher desired   @param key        The secret key   @param keylen     The length of the secret key (octets)   @param nonce      The session nonce (length of the block size of the block cipher)   @param ct         The ciphertext   @param ctlen      The length of the ciphertext (octets)   @param pt         [out] The plaintext   @param tag        The tag to compare against   @param taglen     The length of the tag (octets)   @param stat       [out] The result of the tag comparison (1==valid, 0==invalid)   @return CRYPT_OK if successful regardless of the tag comparison*/int ocb_decrypt_verify_memory(int cipher,    const unsigned char *key,    unsigned long keylen,    const unsigned char *nonce,      const unsigned char *ct,     unsigned long ctlen,          unsigned char *pt,    const unsigned char *tag,    unsigned long taglen,          int           *stat){   int err;   ocb_state *ocb;   LTC_ARGCHK(key    != NULL);   LTC_ARGCHK(nonce  != NULL);   LTC_ARGCHK(pt     != NULL);   LTC_ARGCHK(ct     != NULL);   LTC_ARGCHK(tag    != NULL);   LTC_ARGCHK(stat    != NULL);   /* allocate memory */   ocb = XMALLOC(sizeof(ocb_state));   if (ocb == NULL) {      return CRYPT_MEM;   }   if ((err = ocb_init(ocb, cipher, key, keylen, nonce)) != CRYPT_OK) {      goto LBL_ERR;    }   while (ctlen > (unsigned long)ocb->block_len) {        if ((err = ocb_decrypt(ocb, ct, pt)) != CRYPT_OK) {            goto LBL_ERR;         }        ctlen   -= ocb->block_len;        pt      += ocb->block_len;        ct      += ocb->block_len;   }   err = ocb_done_decrypt(ocb, ct, ctlen, pt, tag, taglen, stat);LBL_ERR:#ifdef LTC_CLEAN_STACK   zeromem(ocb, sizeof(ocb_state));#endif    XFREE(ocb);   return err;}#endif/* $Source: /cvs/libtom/libtomcrypt/src/encauth/ocb/ocb_decrypt_verify_memory.c,v $ *//* $Revision: 1.4 $ *//* $Date: 2006/03/31 14:15:35 $ */