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/* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
#include "mpi.h"
#include "mplogic.h"
#include "ecl.h"
#include "ecl-priv.h"
#include <stdlib.h>
/* Elliptic curve scalar-point multiplication. Computes R(x, y) = k * P(x,
* y). If x, y = NULL, then P is assumed to be the generator (base point)
* of the group of points on the elliptic curve. Input and output values
* are assumed to be NOT field-encoded. */
mp_err
ECPoint_mul(const ECGroup *group, const mp_int *k, const mp_int *px,
const mp_int *py, mp_int *rx, mp_int *ry)
{
mp_err res = MP_OKAY;
mp_int kt;
ARGCHK((k != NULL) && (group != NULL), MP_BADARG);
MP_DIGITS(&kt) = 0;
/* want scalar to be less than or equal to group order */
if (mp_cmp(k, &group->order) > 0) {
MP_CHECKOK(mp_init(&kt));
MP_CHECKOK(mp_mod(k, &group->order, &kt));
} else {
MP_SIGN(&kt) = MP_ZPOS;
MP_USED(&kt) = MP_USED(k);
MP_ALLOC(&kt) = MP_ALLOC(k);
MP_DIGITS(&kt) = MP_DIGITS(k);
}
if ((px == NULL) || (py == NULL)) {
if (group->base_point_mul) {
MP_CHECKOK(group->base_point_mul(&kt, rx, ry, group));
} else {
MP_CHECKOK(group->point_mul(&kt, &group->genx, &group->geny, rx, ry,
group));
}
} else {
if (group->meth->field_enc) {
MP_CHECKOK(group->meth->field_enc(px, rx, group->meth));
MP_CHECKOK(group->meth->field_enc(py, ry, group->meth));
MP_CHECKOK(group->point_mul(&kt, rx, ry, rx, ry, group));
} else {
MP_CHECKOK(group->point_mul(&kt, px, py, rx, ry, group));
}
}
if (group->meth->field_dec) {
MP_CHECKOK(group->meth->field_dec(rx, rx, group->meth));
MP_CHECKOK(group->meth->field_dec(ry, ry, group->meth));
}
CLEANUP:
if (MP_DIGITS(&kt) != MP_DIGITS(k)) {
mp_clear(&kt);
}
return res;
}
/* Elliptic curve scalar-point multiplication. Computes R(x, y) = k1 * G +
* k2 * P(x, y), where G is the generator (base point) of the group of
* points on the elliptic curve. Allows k1 = NULL or { k2, P } = NULL.
* Input and output values are assumed to be NOT field-encoded. */
mp_err
ec_pts_mul_basic(const mp_int *k1, const mp_int *k2, const mp_int *px,
const mp_int *py, mp_int *rx, mp_int *ry,
const ECGroup *group)
{
mp_err res = MP_OKAY;
mp_int sx, sy;
ARGCHK(group != NULL, MP_BADARG);
ARGCHK(!((k1 == NULL) && ((k2 == NULL) || (px == NULL) || (py == NULL))), MP_BADARG);
/* if some arguments are not defined used ECPoint_mul */
if (k1 == NULL) {
return ECPoint_mul(group, k2, px, py, rx, ry);
} else if ((k2 == NULL) || (px == NULL) || (py == NULL)) {
return ECPoint_mul(group, k1, NULL, NULL, rx, ry);
}
MP_DIGITS(&sx) = 0;
MP_DIGITS(&sy) = 0;
MP_CHECKOK(mp_init(&sx));
MP_CHECKOK(mp_init(&sy));
MP_CHECKOK(ECPoint_mul(group, k1, NULL, NULL, &sx, &sy));
MP_CHECKOK(ECPoint_mul(group, k2, px, py, rx, ry));
if (group->meth->field_enc) {
MP_CHECKOK(group->meth->field_enc(&sx, &sx, group->meth));
MP_CHECKOK(group->meth->field_enc(&sy, &sy, group->meth));
MP_CHECKOK(group->meth->field_enc(rx, rx, group->meth));
MP_CHECKOK(group->meth->field_enc(ry, ry, group->meth));
}
MP_CHECKOK(group->point_add(&sx, &sy, rx, ry, rx, ry, group));
if (group->meth->field_dec) {
MP_CHECKOK(group->meth->field_dec(rx, rx, group->meth));
MP_CHECKOK(group->meth->field_dec(ry, ry, group->meth));
}
CLEANUP:
mp_clear(&sx);
mp_clear(&sy);
return res;
}
/* Elliptic curve scalar-point multiplication. Computes R(x, y) = k1 * G +
* k2 * P(x, y), where G is the generator (base point) of the group of
* points on the elliptic curve. Allows k1 = NULL or { k2, P } = NULL.
* Input and output values are assumed to be NOT field-encoded. Uses
* algorithm 15 (simultaneous multiple point multiplication) from Brown,
* Hankerson, Lopez, Menezes. Software Implementation of the NIST
* Elliptic Curves over Prime Fields. */
mp_err
ec_pts_mul_simul_w2(const mp_int *k1, const mp_int *k2, const mp_int *px,
const mp_int *py, mp_int *rx, mp_int *ry,
const ECGroup *group)
{
mp_err res = MP_OKAY;
mp_int precomp[4][4][2];
const mp_int *a, *b;
unsigned int i, j;
int ai, bi, d;
ARGCHK(group != NULL, MP_BADARG);
ARGCHK(!((k1 == NULL) && ((k2 == NULL) || (px == NULL) || (py == NULL))), MP_BADARG);
/* if some arguments are not defined used ECPoint_mul */
if (k1 == NULL) {
return ECPoint_mul(group, k2, px, py, rx, ry);
} else if ((k2 == NULL) || (px == NULL) || (py == NULL)) {
return ECPoint_mul(group, k1, NULL, NULL, rx, ry);
}
/* initialize precomputation table */
for (i = 0; i < 4; i++) {
for (j = 0; j < 4; j++) {
MP_DIGITS(&precomp[i][j][0]) = 0;
MP_DIGITS(&precomp[i][j][1]) = 0;
}
}
for (i = 0; i < 4; i++) {
for (j = 0; j < 4; j++) {
MP_CHECKOK(mp_init_size(&precomp[i][j][0],
ECL_MAX_FIELD_SIZE_DIGITS));
MP_CHECKOK(mp_init_size(&precomp[i][j][1],
ECL_MAX_FIELD_SIZE_DIGITS));
}
}
/* fill precomputation table */
/* assign {k1, k2} = {a, b} such that len(a) >= len(b) */
if (mpl_significant_bits(k1) < mpl_significant_bits(k2)) {
a = k2;
b = k1;
if (group->meth->field_enc) {
MP_CHECKOK(group->meth->field_enc(px, &precomp[1][0][0], group->meth));
MP_CHECKOK(group->meth->field_enc(py, &precomp[1][0][1], group->meth));
} else {
MP_CHECKOK(mp_copy(px, &precomp[1][0][0]));
MP_CHECKOK(mp_copy(py, &precomp[1][0][1]));
}
MP_CHECKOK(mp_copy(&group->genx, &precomp[0][1][0]));
MP_CHECKOK(mp_copy(&group->geny, &precomp[0][1][1]));
} else {
a = k1;
b = k2;
MP_CHECKOK(mp_copy(&group->genx, &precomp[1][0][0]));
MP_CHECKOK(mp_copy(&group->geny, &precomp[1][0][1]));
if (group->meth->field_enc) {
MP_CHECKOK(group->meth->field_enc(px, &precomp[0][1][0], group->meth));
MP_CHECKOK(group->meth->field_enc(py, &precomp[0][1][1], group->meth));
} else {
MP_CHECKOK(mp_copy(px, &precomp[0][1][0]));
MP_CHECKOK(mp_copy(py, &precomp[0][1][1]));
}
}
/* precompute [*][0][*] */
mp_zero(&precomp[0][0][0]);
mp_zero(&precomp[0][0][1]);
MP_CHECKOK(group->point_dbl(&precomp[1][0][0], &precomp[1][0][1],
&precomp[2][0][0], &precomp[2][0][1], group));
MP_CHECKOK(group->point_add(&precomp[1][0][0], &precomp[1][0][1],
&precomp[2][0][0], &precomp[2][0][1],
&precomp[3][0][0], &precomp[3][0][1], group));
/* precompute [*][1][*] */
for (i = 1; i < 4; i++) {
MP_CHECKOK(group->point_add(&precomp[0][1][0], &precomp[0][1][1],
&precomp[i][0][0], &precomp[i][0][1],
&precomp[i][1][0], &precomp[i][1][1], group));
}
/* precompute [*][2][*] */
MP_CHECKOK(group->point_dbl(&precomp[0][1][0], &precomp[0][1][1],
&precomp[0][2][0], &precomp[0][2][1], group));
for (i = 1; i < 4; i++) {
MP_CHECKOK(group->point_add(&precomp[0][2][0], &precomp[0][2][1],
&precomp[i][0][0], &precomp[i][0][1],
&precomp[i][2][0], &precomp[i][2][1], group));
}
/* precompute [*][3][*] */
MP_CHECKOK(group->point_add(&precomp[0][1][0], &precomp[0][1][1],
&precomp[0][2][0], &precomp[0][2][1],
&precomp[0][3][0], &precomp[0][3][1], group));
for (i = 1; i < 4; i++) {
MP_CHECKOK(group->point_add(&precomp[0][3][0], &precomp[0][3][1],
&precomp[i][0][0], &precomp[i][0][1],
&precomp[i][3][0], &precomp[i][3][1], group));
}
d = (mpl_significant_bits(a) + 1) / 2;
/* R = inf */
mp_zero(rx);
mp_zero(ry);
for (i = d; i-- > 0;) {
ai = MP_GET_BIT(a, 2 * i + 1);
ai <<= 1;
ai |= MP_GET_BIT(a, 2 * i);
bi = MP_GET_BIT(b, 2 * i + 1);
bi <<= 1;
bi |= MP_GET_BIT(b, 2 * i);
/* R = 2^2 * R */
MP_CHECKOK(group->point_dbl(rx, ry, rx, ry, group));
MP_CHECKOK(group->point_dbl(rx, ry, rx, ry, group));
/* R = R + (ai * A + bi * B) */
MP_CHECKOK(group->point_add(rx, ry, &precomp[ai][bi][0],
&precomp[ai][bi][1], rx, ry, group));
}
if (group->meth->field_dec) {
MP_CHECKOK(group->meth->field_dec(rx, rx, group->meth));
MP_CHECKOK(group->meth->field_dec(ry, ry, group->meth));
}
CLEANUP:
for (i = 0; i < 4; i++) {
for (j = 0; j < 4; j++) {
mp_clear(&precomp[i][j][0]);
mp_clear(&precomp[i][j][1]);
}
}
return res;
}
/* Elliptic curve scalar-point multiplication. Computes R(x, y) = k1 * G +
* k2 * P(x, y), where G is the generator (base point) of the group of
* points on the elliptic curve. Allows k1 = NULL or { k2, P } = NULL.
* Input and output values are assumed to be NOT field-encoded. */
mp_err
ECPoints_mul(const ECGroup *group, const mp_int *k1, const mp_int *k2,
const mp_int *px, const mp_int *py, mp_int *rx, mp_int *ry)
{
mp_err res = MP_OKAY;
mp_int k1t, k2t;
const mp_int *k1p, *k2p;
MP_DIGITS(&k1t) = 0;
MP_DIGITS(&k2t) = 0;
ARGCHK(group != NULL, MP_BADARG);
/* want scalar to be less than or equal to group order */
if (k1 != NULL) {
if (mp_cmp(k1, &group->order) >= 0) {
MP_CHECKOK(mp_init(&k1t));
MP_CHECKOK(mp_mod(k1, &group->order, &k1t));
k1p = &k1t;
} else {
k1p = k1;
}
} else {
k1p = k1;
}
if (k2 != NULL) {
if (mp_cmp(k2, &group->order) >= 0) {
MP_CHECKOK(mp_init(&k2t));
MP_CHECKOK(mp_mod(k2, &group->order, &k2t));
k2p = &k2t;
} else {
k2p = k2;
}
} else {
k2p = k2;
}
/* if points_mul is defined, then use it */
if (group->points_mul) {
res = group->points_mul(k1p, k2p, px, py, rx, ry, group);
} else {
res = ec_pts_mul_simul_w2(k1p, k2p, px, py, rx, ry, group);
}
CLEANUP:
mp_clear(&k1t);
mp_clear(&k2t);
return res;
}
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