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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://libtom.org
*/
#include "tomcrypt.h"
/**
@file xcbc_done.c
XCBC Support, terminate the state
*/
#ifdef LTC_XCBC
/** Terminate the XCBC-MAC state
@param xcbc XCBC state to terminate
@param out [out] Destination for the MAC tag
@param outlen [in/out] Destination size and final tag size
Return CRYPT_OK on success
*/
int xcbc_done(xcbc_state *xcbc, unsigned char *out, unsigned long *outlen)
{
int err, x;
LTC_ARGCHK(xcbc != NULL);
LTC_ARGCHK(out != NULL);
/* check structure */
if ((err = cipher_is_valid(xcbc->cipher)) != CRYPT_OK) {
return err;
}
if ((xcbc->blocksize > cipher_descriptor[xcbc->cipher].block_length) || (xcbc->blocksize < 0) ||
(xcbc->buflen > xcbc->blocksize) || (xcbc->buflen < 0)) {
return CRYPT_INVALID_ARG;
}
/* which key do we use? */
if (xcbc->buflen == xcbc->blocksize) {
/* k2 */
for (x = 0; x < xcbc->blocksize; x++) {
xcbc->IV[x] ^= xcbc->K[1][x];
}
} else {
xcbc->IV[xcbc->buflen] ^= 0x80;
/* k3 */
for (x = 0; x < xcbc->blocksize; x++) {
xcbc->IV[x] ^= xcbc->K[2][x];
}
}
/* encrypt */
cipher_descriptor[xcbc->cipher].ecb_encrypt(xcbc->IV, xcbc->IV, &xcbc->key);
cipher_descriptor[xcbc->cipher].done(&xcbc->key);
/* extract tag */
for (x = 0; x < xcbc->blocksize && (unsigned long)x < *outlen; x++) {
out[x] = xcbc->IV[x];
}
*outlen = x;
#ifdef LTC_CLEAN_STACK
zeromem(xcbc, sizeof(*xcbc));
#endif
return CRYPT_OK;
}
#endif
/* $Source$ */
/* $Revision$ */
/* $Date$ */
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