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/* 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.org
*/
/**
@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: 1.3 $ */
/* $Date: 2005/05/05 14:35:58 $ */
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