/* get normalization value */
static int montgomery_normalization(void *a, void *b)
{
LTC_ARGCHK(a != NULL);
LTC_ARGCHK(b != NULL);
mpa_asize_t s;
s = __mpanum_size((mpanum) b);
twoexpt(a, s * MPA_WORD_SIZE);
mpa_mod((mpanum) a, (const mpanum) a, (const mpanum) b, external_mem_pool);
return CRYPT_OK;
}
static int mod(void *a, void *b, void *c)
{
LTC_ARGCHK(a != NULL);
LTC_ARGCHK(b != NULL);
LTC_ARGCHK(c != NULL);
mpa_mod((mpanum) c, (const mpanum) a, (const mpanum) b, external_mem_pool);
if (mpa_cmp_short(c, 0) < 0) {
mpa_add(c, c, b, external_mem_pool);
}
return CRYPT_OK;
}
/*
* TEE_BigIntMod
*/
void TEE_BigIntMod(TEE_BigInt *dest, const TEE_BigInt *op,
const TEE_BigInt *n)
{
mpanum mpa_dest = (mpa_num_base *)dest;
mpanum mpa_op = (mpa_num_base *)op;
mpanum mpa_n = (mpa_num_base *)n;
if (TEE_BigIntCmpS32(n, 2) < 0)
TEE_BigInt_Panic("Modulus is too short");
mpa_mod(mpa_dest, mpa_op, mpa_n, mempool);
if (mpa_cmp_short(mpa_dest, 0) < 0)
mpa_add(mpa_dest, mpa_dest, mpa_n, mempool);
}
/* reduce */
static int montgomery_reduce(void *a, void *b, void *c)
{
LTC_ARGCHK(a != NULL);
LTC_ARGCHK(b != NULL);
LTC_ARGCHK(c != NULL);
mpanum tmp;
init((void **)&tmp);
// WARNING
// Workaround for a bug when a > b (a greater than the modulus)
if (compare(a, b) == LTC_MP_GT) {
mpa_mod((mpanum) a, (const mpanum) a, (const mpanum) b, external_mem_pool);
}
mpa_montgomery_mul(tmp,
(mpanum) a,
mpa_constant_one(),
(mpanum) b,
((mpa_fmm_context) c)->n_inv,
external_mem_pool);
mpa_copy(a, tmp);
deinit(tmp);
return CRYPT_OK;
}
