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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_aad.c
GCM implementation, Add AAD data to the stream, by Tom St Denis
*/
#include "tomcrypt.h"
#ifdef GCM_MODE
/**
Add AAD to the GCM state
@param gcm The GCM state
@param adata The additional authentication data to add to the GCM state
@param adatalen The length of the AAD data.
@return CRYPT_OK on success
*/
int gcm_add_aad(gcm_state *gcm,
const unsigned char *adata, unsigned long adatalen)
{
unsigned long x;
int err;
#ifdef LTC_FAST
unsigned long y;
#endif
LTC_ARGCHK(gcm != NULL);
if (adatalen > 0) {
LTC_ARGCHK(adata != NULL);
}
if (gcm->buflen > 16 || gcm->buflen < 0) {
return CRYPT_INVALID_ARG;
}
if ((err = cipher_is_valid(gcm->cipher)) != CRYPT_OK) {
return err;
}
/* in IV mode? */
if (gcm->mode == GCM_MODE_IV) {
/* let's process the IV */
if (gcm->ivmode || gcm->buflen != 12) {
for (x = 0; x < (unsigned long)gcm->buflen; x++) {
gcm->X[x] ^= gcm->buf[x];
}
if (gcm->buflen) {
gcm->totlen += gcm->buflen * CONST64(8);
gcm_mult_h(gcm, gcm->X);
}
/* mix in the length */
zeromem(gcm->buf, 8);
STORE64H(gcm->totlen, gcm->buf+8);
for (x = 0; x < 16; x++) {
gcm->X[x] ^= gcm->buf[x];
}
gcm_mult_h(gcm, gcm->X);
/* copy counter out */
XMEMCPY(gcm->Y, gcm->X, 16);
zeromem(gcm->X, 16);
} else {
XMEMCPY(gcm->Y, gcm->buf, 12);
gcm->Y[12] = 0;
gcm->Y[13] = 0;
gcm->Y[14] = 0;
gcm->Y[15] = 1;
}
XMEMCPY(gcm->Y_0, gcm->Y, 16);
zeromem(gcm->buf, 16);
gcm->buflen = 0;
gcm->totlen = 0;
gcm->mode = GCM_MODE_AAD;
}
if (gcm->mode != GCM_MODE_AAD || gcm->buflen >= 16) {
return CRYPT_INVALID_ARG;
}
x = 0;
#ifdef LTC_FAST
if (gcm->buflen == 0) {
for (x = 0; x < (adatalen & ~15); x += 16) {
for (y = 0; y < 16; y += sizeof(LTC_FAST_TYPE)) {
*((LTC_FAST_TYPE*)(&gcm->X[y])) ^= *((LTC_FAST_TYPE*)(&adata[x + y]));
}
gcm_mult_h(gcm, gcm->X);
gcm->totlen += 128;
}
adata += x;
}
#endif
/* start adding AAD data to the state */
for (; x < adatalen; x++) {
gcm->X[gcm->buflen++] ^= *adata++;
if (gcm->buflen == 16) {
/* GF mult it */
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_aad.c,v $ */
/* $Revision: 1.16 $ */
/* $Date: 2006/09/23 19:24:21 $ */
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