118 lines
3.1 KiB
C
118 lines
3.1 KiB
C
/* 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@iahu.ca, http://libtomcrypt.org
|
|
*/
|
|
|
|
/* OCB Implementation by Tom St Denis */
|
|
#include "mycrypt.h"
|
|
|
|
#ifdef OCB_MODE
|
|
|
|
static const struct {
|
|
int len;
|
|
unsigned char poly_div[MAXBLOCKSIZE],
|
|
poly_mul[MAXBLOCKSIZE];
|
|
} polys[] = {
|
|
{
|
|
8,
|
|
{ 0x80, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x0D },
|
|
{ 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x1B }
|
|
}, {
|
|
16,
|
|
{ 0x80, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
|
|
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x43 },
|
|
{ 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
|
|
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x87 }
|
|
}
|
|
};
|
|
|
|
int ocb_init(ocb_state *ocb, int cipher,
|
|
const unsigned char *key, unsigned long keylen, const unsigned char *nonce)
|
|
{
|
|
int poly, x, y, m, err;
|
|
|
|
_ARGCHK(ocb != NULL);
|
|
_ARGCHK(key != NULL);
|
|
_ARGCHK(nonce != NULL);
|
|
|
|
/* valid cipher? */
|
|
if ((err = cipher_is_valid(cipher)) != CRYPT_OK) {
|
|
return err;
|
|
}
|
|
|
|
/* determine which polys to use */
|
|
ocb->block_len = cipher_descriptor[cipher].block_length;
|
|
for (poly = 0; poly < (int)(sizeof(polys)/sizeof(polys[0])); poly++) {
|
|
if (polys[poly].len == ocb->block_len) {
|
|
break;
|
|
}
|
|
}
|
|
if (polys[poly].len != ocb->block_len) {
|
|
return CRYPT_INVALID_ARG;
|
|
}
|
|
|
|
/* schedule the key */
|
|
if ((err = cipher_descriptor[cipher].setup(key, keylen, 0, &ocb->key)) != CRYPT_OK) {
|
|
return err;
|
|
}
|
|
|
|
/* find L = E[0] */
|
|
zeromem(ocb->L, ocb->block_len);
|
|
cipher_descriptor[cipher].ecb_encrypt(ocb->L, ocb->L, &ocb->key);
|
|
|
|
/* find R = E[N xor L] */
|
|
for (x = 0; x < ocb->block_len; x++) {
|
|
ocb->R[x] = ocb->L[x] ^ nonce[x];
|
|
}
|
|
cipher_descriptor[cipher].ecb_encrypt(ocb->R, ocb->R, &ocb->key);
|
|
|
|
/* find Ls[i] = L << i for i == 0..31 */
|
|
XMEMCPY(ocb->Ls[0], ocb->L, ocb->block_len);
|
|
for (x = 1; x < 32; x++) {
|
|
m = ocb->Ls[x-1][0] >> 7;
|
|
for (y = 0; y < ocb->block_len-1; y++) {
|
|
ocb->Ls[x][y] = ((ocb->Ls[x-1][y] << 1) | (ocb->Ls[x-1][y+1] >> 7)) & 255;
|
|
}
|
|
ocb->Ls[x][ocb->block_len-1] = (ocb->Ls[x-1][ocb->block_len-1] << 1) & 255;
|
|
|
|
if (m == 1) {
|
|
for (y = 0; y < ocb->block_len; y++) {
|
|
ocb->Ls[x][y] ^= polys[poly].poly_mul[y];
|
|
}
|
|
}
|
|
}
|
|
|
|
/* find Lr = L / x */
|
|
m = ocb->L[ocb->block_len-1] & 1;
|
|
|
|
/* shift right */
|
|
for (x = ocb->block_len - 1; x > 0; x--) {
|
|
ocb->Lr[x] = ((ocb->L[x] >> 1) | (ocb->L[x-1] << 7)) & 255;
|
|
}
|
|
ocb->Lr[0] = ocb->L[0] >> 1;
|
|
|
|
if (m == 1) {
|
|
for (x = 0; x < ocb->block_len; x++) {
|
|
ocb->Lr[x] ^= polys[poly].poly_div[x];
|
|
}
|
|
}
|
|
|
|
/* set Li, checksum */
|
|
zeromem(ocb->Li, ocb->block_len);
|
|
zeromem(ocb->checksum, ocb->block_len);
|
|
|
|
/* set other params */
|
|
ocb->block_index = 1;
|
|
ocb->cipher = cipher;
|
|
|
|
return CRYPT_OK;
|
|
}
|
|
|
|
#endif
|