139 lines
4.0 KiB
C
139 lines
4.0 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@gmail.com, http://libtom.org
|
|
*/
|
|
|
|
/**
|
|
@file ocb3_init.c
|
|
OCB implementation, initialize state, by Tom St Denis
|
|
*/
|
|
#include "tomcrypt.h"
|
|
|
|
#ifdef LTC_OCB3_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 }
|
|
}
|
|
};
|
|
|
|
/**
|
|
Initialize an OCB context
|
|
@param ocb [out] The destination of the OCB state
|
|
@param cipher The index of the desired cipher
|
|
@param key The secret key
|
|
@param keylen The length of the secret key (octets)
|
|
@param nonce The session nonce
|
|
@param noncelen The length of the session nonce (octets)
|
|
@return CRYPT_OK if successful
|
|
*/
|
|
int ocb3_init(ocb3_state *ocb, int cipher,
|
|
const unsigned char *key, unsigned long keylen,
|
|
const unsigned char *nonce, unsigned long noncelen)
|
|
{
|
|
int poly, x, y, m, err;
|
|
unsigned char *previous, *current;
|
|
|
|
LTC_ARGCHK(ocb != NULL);
|
|
LTC_ARGCHK(key != NULL);
|
|
LTC_ARGCHK(nonce != NULL);
|
|
|
|
/* valid cipher? */
|
|
if ((err = cipher_is_valid(cipher)) != CRYPT_OK) {
|
|
return err;
|
|
}
|
|
ocb->cipher = cipher;
|
|
|
|
/* determine which polys to use */
|
|
ocb->block_len = cipher_descriptor[cipher].block_length;
|
|
x = (int)(sizeof(polys)/sizeof(polys[0]));
|
|
for (poly = 0; poly < x; poly++) {
|
|
if (polys[poly].len == ocb->block_len) {
|
|
break;
|
|
}
|
|
}
|
|
if (poly == x) {
|
|
return CRYPT_INVALID_ARG; /* block_len not found in polys */
|
|
}
|
|
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;
|
|
}
|
|
|
|
/* L_* = ENCIPHER(K, zeros(128)) */
|
|
zeromem(ocb->L_star, ocb->block_len);
|
|
if ((err = cipher_descriptor[cipher].ecb_encrypt(ocb->L_star, ocb->L_star, &ocb->key)) != CRYPT_OK) {
|
|
return err;
|
|
}
|
|
|
|
/* compute L_$, L_0, L_1, ... */
|
|
for (x = -1; x < 32; x++) {
|
|
if (x == -1) { /* gonna compute: L_$ = double(L_*) */
|
|
current = ocb->L_dollar;
|
|
previous = ocb->L_star;
|
|
}
|
|
else if (x == 0) { /* gonna compute: L_0 = double(L_$) */
|
|
current = ocb->L_[0];
|
|
previous = ocb->L_dollar;
|
|
}
|
|
else { /* gonna compute: L_i = double(L_{i-1}) for every integer i > 0 */
|
|
current = ocb->L_[x];
|
|
previous = ocb->L_[x-1];
|
|
}
|
|
m = previous[0] >> 7;
|
|
for (y = 0; y < ocb->block_len-1; y++) {
|
|
current[y] = ((previous[y] << 1) | (previous[y+1] >> 7)) & 255;
|
|
}
|
|
current[ocb->block_len-1] = (previous[ocb->block_len-1] << 1) & 255;
|
|
if (m == 1) {
|
|
/* current[] = current[] XOR polys[poly].poly_mul[]*/
|
|
ocb3_int_xor_blocks(current, current, polys[poly].poly_mul, ocb->block_len);
|
|
}
|
|
}
|
|
|
|
/* initialize ocb->Offset_current = Offset_0 */
|
|
ocb3_int_calc_offset_zero(ocb, nonce, noncelen);
|
|
|
|
/* initialize checksum to all zeros */
|
|
zeromem(ocb->checksum, ocb->block_len);
|
|
|
|
/* set block index */
|
|
ocb->block_index = 1;
|
|
|
|
/* initialize AAD related stuff */
|
|
ocb->ablock_index = 1;
|
|
ocb->adata_buffer_bytes = 0;
|
|
zeromem(ocb->aOffset_current, ocb->block_len);
|
|
zeromem(ocb->aSum_current, ocb->block_len);
|
|
|
|
return CRYPT_OK;
|
|
}
|
|
|
|
#endif
|
|
|
|
/* $Source$ */
|
|
/* $Revision$ */
|
|
/* $Date$ */
|