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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 lrw_process.c
LRW_MODE implementation, Encrypt/decrypt blocks, Tom St Denis
*/
#ifdef LTC_LRW_MODE
/**
Process blocks with LRW, since decrypt/encrypt are largely the same they share this code.
@param pt The "input" data
@param ct [out] The "output" data
@param len The length of the input, must be a multiple of 128-bits (16 octets)
@param mode LRW_ENCRYPT or LRW_DECRYPT
@param lrw The LRW state
@return CRYPT_OK if successful
*/
int lrw_process(const unsigned char *pt, unsigned char *ct, unsigned long len, int mode, symmetric_LRW *lrw)
{
unsigned char prod[16];
int x, err;
#ifdef LRW_TABLES
int y;
#endif
LTC_ARGCHK(pt != NULL);
LTC_ARGCHK(ct != NULL);
LTC_ARGCHK(lrw != NULL);
if (len & 15) {
return CRYPT_INVALID_ARG;
}
while (len) {
/* copy pad */
XMEMCPY(prod, lrw->pad, 16);
/* increment IV */
for (x = 15; x >= 0; x--) {
lrw->IV[x] = (lrw->IV[x] + 1) & 255;
if (lrw->IV[x]) {
break;
}
}
/* update pad */
#ifdef LRW_TABLES
/* for each byte changed we undo it's affect on the pad then add the new product */
for (; x < 16; x++) {
#ifdef LTC_FAST
for (y = 0; y < 16; y += sizeof(LTC_FAST_TYPE)) {
*((LTC_FAST_TYPE *)(lrw->pad + y)) ^= *((LTC_FAST_TYPE *)(&lrw->PC[x][lrw->IV[x]][y])) ^ *((LTC_FAST_TYPE *)(&lrw->PC[x][(lrw->IV[x]-1)&255][y]));
}
#else
for (y = 0; y < 16; y++) {
lrw->pad[y] ^= lrw->PC[x][lrw->IV[x]][y] ^ lrw->PC[x][(lrw->IV[x]-1)&255][y];
}
#endif
}
#else
gcm_gf_mult(lrw->tweak, lrw->IV, lrw->pad);
#endif
/* xor prod */
#ifdef LTC_FAST
for (x = 0; x < 16; x += sizeof(LTC_FAST_TYPE)) {
*((LTC_FAST_TYPE *)(ct + x)) = *((LTC_FAST_TYPE *)(pt + x)) ^ *((LTC_FAST_TYPE *)(prod + x));
}
#else
for (x = 0; x < 16; x++) {
ct[x] = pt[x] ^ prod[x];
}
#endif
/* send through cipher */
if (mode == LRW_ENCRYPT) {
if ((err = cipher_descriptor[lrw->cipher].ecb_encrypt(ct, ct, &lrw->key)) != CRYPT_OK) {
return err;
}
} else {
if ((err = cipher_descriptor[lrw->cipher].ecb_decrypt(ct, ct, &lrw->key)) != CRYPT_OK) {
return err;
}
}
/* xor prod */
#ifdef LTC_FAST
for (x = 0; x < 16; x += sizeof(LTC_FAST_TYPE)) {
*((LTC_FAST_TYPE *)(ct + x)) = *((LTC_FAST_TYPE *)(ct + x)) ^ *((LTC_FAST_TYPE *)(prod + x));
}
#else
for (x = 0; x < 16; x++) {
ct[x] = ct[x] ^ prod[x];
}
#endif
/* move to next */
pt += 16;
ct += 16;
len -= 16;
}
return CRYPT_OK;
}
#endif
/* $Source: /cvs/libtom/libtomcrypt/src/modes/lrw/lrw_process.c,v $ */
/* $Revision: 1.10 $ */
/* $Date: 2006/06/29 01:53:13 $ */
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