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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.com
*/
#include "tomcrypt.h"
/**
@file omac_done.c
OMAC1 support, terminate a stream, Tom St Denis
*/
#ifdef LTC_OMAC
/**
Terminate an OMAC stream
@param omac The OMAC state
@param out [out] Destination for the authentication tag
@param outlen [in/out] The max size and resulting size of the authentication tag
@return CRYPT_OK if successful
*/
int omac_done(omac_state *omac, unsigned char *out, unsigned long *outlen)
{
int err, mode;
unsigned x;
LTC_ARGCHK(omac != NULL);
LTC_ARGCHK(out != NULL);
LTC_ARGCHK(outlen != NULL);
if ((err = cipher_is_valid(omac->cipher_idx)) != CRYPT_OK) {
return err;
}
if ((omac->buflen > (int)sizeof(omac->block)) || (omac->buflen < 0) ||
(omac->blklen > (int)sizeof(omac->block)) || (omac->buflen > omac->blklen)) {
return CRYPT_INVALID_ARG;
}
/* figure out mode */
if (omac->buflen != omac->blklen) {
/* add the 0x80 byte */
omac->block[omac->buflen++] = 0x80;
/* pad with 0x00 */
while (omac->buflen < omac->blklen) {
omac->block[omac->buflen++] = 0x00;
}
mode = 1;
} else {
mode = 0;
}
/* now xor prev + Lu[mode] */
for (x = 0; x < (unsigned)omac->blklen; x++) {
omac->block[x] ^= omac->prev[x] ^ omac->Lu[mode][x];
}
/* encrypt it */
if ((err = cipher_descriptor[omac->cipher_idx].ecb_encrypt(omac->block, omac->block, &omac->key)) != CRYPT_OK) {
return err;
}
cipher_descriptor[omac->cipher_idx].done(&omac->key);
/* output it */
for (x = 0; x < (unsigned)omac->blklen && x < *outlen; x++) {
out[x] = omac->block[x];
}
*outlen = x;
#ifdef LTC_CLEAN_STACK
zeromem(omac, sizeof(*omac));
#endif
return CRYPT_OK;
}
#endif
/* $Source: /cvs/libtom/libtomcrypt/src/mac/omac/omac_done.c,v $ */
/* $Revision: 1.7 $ */
/* $Date: 2006/11/03 00:39:49 $ */
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