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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
*/
/**
@file gcm_add_iv.c
GCM implementation, add IV data to the state, by Tom St Denis
*/
#include "tomcrypt.h"
#ifdef GCM_MODE
/**
Add IV data to the GCM state
@param gcm The GCM state
@param IV The initial value data to add
@param IVlen The length of the IV
@return CRYPT_OK on success
*/
int gcm_add_iv(gcm_state *gcm,
const unsigned char *IV, unsigned long IVlen)
{
unsigned long x, y;
int err;
LTC_ARGCHK(gcm != NULL);
if (IVlen > 0) {
LTC_ARGCHK(IV != NULL);
}
/* must be in IV mode */
if (gcm->mode != GCM_MODE_IV) {
return CRYPT_INVALID_ARG;
}
if (gcm->buflen >= 16 || gcm->buflen < 0) {
return CRYPT_INVALID_ARG;
}
if ((err = cipher_is_valid(gcm->cipher)) != CRYPT_OK) {
return err;
}
/* trip the ivmode flag */
if (IVlen + gcm->buflen > 12) {
gcm->ivmode |= 1;
}
x = 0;
#ifdef LTC_FAST
if (gcm->buflen == 0) {
for (x = 0; x < (IVlen & ~15); x += 16) {
for (y = 0; y < 16; y += sizeof(LTC_FAST_TYPE)) {
*((LTC_FAST_TYPE*)(&gcm->X[y])) ^= *((LTC_FAST_TYPE*)(&IV[x + y]));
}
gcm_mult_h(gcm, gcm->X);
gcm->totlen += 128;
}
IV += x;
}
#endif
/* start adding IV data to the state */
for (; x < IVlen; x++) {
gcm->buf[gcm->buflen++] = *IV++;
if (gcm->buflen == 16) {
/* GF mult it */
for (y = 0; y < 16; y++) {
gcm->X[y] ^= gcm->buf[y];
}
gcm_mult_h(gcm, gcm->X);
gcm->buflen = 0;
gcm->totlen += 128;
}
}
return CRYPT_OK;
}
#endif
/* $Source: /cvs/libtom/libtomcrypt/src/encauth/gcm/gcm_add_iv.c,v $ */
/* $Revision: 1.7 $ */
/* $Date: 2006/03/31 14:15:35 $ */
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