void
ecc_modp_add (const struct ecc_curve *ecc, mp_limb_t *rp,
const mp_limb_t *ap, const mp_limb_t *bp)
{
mp_limb_t cy;
cy = mpn_add_n (rp, ap, bp, ecc->size);
cy = cnd_add_n (cy, rp, ecc->Bmodp, ecc->size);
cy = cnd_add_n (cy, rp, ecc->Bmodp, ecc->size);
assert (cy == 0);
}
void
ecc_modp_addmul_1 (const struct ecc_curve *ecc, mp_limb_t *rp,
const mp_limb_t *ap, mp_limb_t b)
{
mp_limb_t hi;
assert (b <= 0xffffffff);
hi = mpn_addmul_1 (rp, ap, ecc->size, b);
hi = mpn_addmul_1 (rp, ecc->Bmodp, ecc->size, hi);
assert (hi <= 1);
hi = cnd_add_n (hi, rp, ecc->Bmodp, ecc->size);
/* Sufficient roughly if b < B^size / p */
assert (hi == 0);
}
/* Reduce from 12 to 9 limbs (top limb small)*/
cy = mpn_add_n (rp + 2, rp + 2, rp + 8, 4);
cy = sec_add_1 (rp + 6, rp + 6, 2, cy);
cy += mpn_add_n (rp + 4, rp + 4, rp + 8, 4);
assert (cy <= 2);
rp[8] = cy;
/* Reduce from 9 to 6 limbs */
cy = mpn_add_n (rp, rp, rp + 6, 3);
cy = sec_add_1 (rp + 3, rp + 3, 2, cy);
cy += mpn_add_n (rp + 2, rp + 2, rp + 6, 3);
cy = sec_add_1 (rp + 5, rp + 5, 1, cy);
assert (cy <= 1);
cy = cnd_add_n (cy, rp, ecc_Bmodp, 6);
assert (cy == 0);
}
#elif GMP_NUMB_BITS == 64
/* p is 3 limbs, p = B^3 - B - 1 */
static void
ecc_192_modp (const struct ecc_modulo *m UNUSED, mp_limb_t *rp)
{
mp_limb_t cy;
/* Reduce from 6 to 5 limbs (top limb small)*/
cy = mpn_add_n (rp + 1, rp + 1, rp + 4, 2);
cy = sec_add_1 (rp + 3, rp + 3, 1, cy);
cy += mpn_add_n (rp + 2, rp + 2, rp + 4, 2);
assert (cy <= 2);
