/**
* Expand the AES key into a Python (byte) string object.
*/
EXPORT_SYM int ghash_expand(const uint8_t h[16], t_exp_key **ghash_tables)
{
t_exp_key *exp_key;
if (NULL==h || NULL==ghash_tables)
return ERR_NULL;
*ghash_tables = exp_key = calloc(1, sizeof(t_exp_key));
if (NULL == exp_key)
return ERR_MEMORY;
exp_key->offset = ALIGNMENT - ((uintptr_t)exp_key->buffer & (ALIGNMENT-1));
make_v_tables(h, (t_v_tables*)(exp_key->buffer + exp_key->offset));
return 0;
}
/**
* Expand a hash key into a set of tables that will speed
* up GHASH.
*
* \param tables Pointer to allocated memory that will hold
* the tables.
* \param h The hash key.
*/
static int ghash_expand(t_key_tables *key_tables, const uint8_t h[16])
{
int i;
const t_v_tables *v_tables;
v_tables = make_v_tables(h);
if (v_tables==NULL) {
return -1;
}
for (i=0; i<16; i++) {
int j;
for (j=0; j<256; j++) {
/** Z = H*j*P^{8i} **/
gcm_mult3(&((*key_tables)[i][j][0]), j, i, v_tables);
}
}
free(v_tables);
return 0;
}