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yuzu/externals/libressl/crypto/ec/ecp_smpl.c

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early-access version 1255
2020-12-28 19:15:37 +04:00
/* $OpenBSD: ecp_smpl.c,v 1.29 2018/11/15 05:53:31 tb Exp $ */
/* Includes code written by Lenka Fibikova <fibikova@exp-math.uni-essen.de>
* for the OpenSSL project.
* Includes code written by Bodo Moeller for the OpenSSL project.
*/
/* ====================================================================
* Copyright (c) 1998-2002 The OpenSSL Project. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
*
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in
* the documentation and/or other materials provided with the
* distribution.
*
* 3. All advertising materials mentioning features or use of this
* software must display the following acknowledgment:
* "This product includes software developed by the OpenSSL Project
* for use in the OpenSSL Toolkit. (http://www.openssl.org/)"
*
* 4. The names "OpenSSL Toolkit" and "OpenSSL Project" must not be used to
* endorse or promote products derived from this software without
* prior written permission. For written permission, please contact
* openssl-core@openssl.org.
*
* 5. Products derived from this software may not be called "OpenSSL"
* nor may "OpenSSL" appear in their names without prior written
* permission of the OpenSSL Project.
*
* 6. Redistributions of any form whatsoever must retain the following
* acknowledgment:
* "This product includes software developed by the OpenSSL Project
* for use in the OpenSSL Toolkit (http://www.openssl.org/)"
*
* THIS SOFTWARE IS PROVIDED BY THE OpenSSL PROJECT ``AS IS'' AND ANY
* EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE OpenSSL PROJECT OR
* ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
* LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
* STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
* OF THE POSSIBILITY OF SUCH DAMAGE.
* ====================================================================
*
* This product includes cryptographic software written by Eric Young
* (eay@cryptsoft.com). This product includes software written by Tim
* Hudson (tjh@cryptsoft.com).
*
*/
/* ====================================================================
* Copyright 2002 Sun Microsystems, Inc. ALL RIGHTS RESERVED.
* Portions of this software developed by SUN MICROSYSTEMS, INC.,
* and contributed to the OpenSSL project.
*/
#include <openssl/err.h>
#include "bn_lcl.h"
#include "ec_lcl.h"
const EC_METHOD *
EC_GFp_simple_method(void)
{
static const EC_METHOD ret = {
.flags = EC_FLAGS_DEFAULT_OCT,
.field_type = NID_X9_62_prime_field,
.group_init = ec_GFp_simple_group_init,
.group_finish = ec_GFp_simple_group_finish,
.group_clear_finish = ec_GFp_simple_group_clear_finish,
.group_copy = ec_GFp_simple_group_copy,
.group_set_curve = ec_GFp_simple_group_set_curve,
.group_get_curve = ec_GFp_simple_group_get_curve,
.group_get_degree = ec_GFp_simple_group_get_degree,
.group_check_discriminant =
ec_GFp_simple_group_check_discriminant,
.point_init = ec_GFp_simple_point_init,
.point_finish = ec_GFp_simple_point_finish,
.point_clear_finish = ec_GFp_simple_point_clear_finish,
.point_copy = ec_GFp_simple_point_copy,
.point_set_to_infinity = ec_GFp_simple_point_set_to_infinity,
.point_set_Jprojective_coordinates_GFp =
ec_GFp_simple_set_Jprojective_coordinates_GFp,
.point_get_Jprojective_coordinates_GFp =
ec_GFp_simple_get_Jprojective_coordinates_GFp,
.point_set_affine_coordinates =
ec_GFp_simple_point_set_affine_coordinates,
.point_get_affine_coordinates =
ec_GFp_simple_point_get_affine_coordinates,
.add = ec_GFp_simple_add,
.dbl = ec_GFp_simple_dbl,
.invert = ec_GFp_simple_invert,
.is_at_infinity = ec_GFp_simple_is_at_infinity,
.is_on_curve = ec_GFp_simple_is_on_curve,
.point_cmp = ec_GFp_simple_cmp,
.make_affine = ec_GFp_simple_make_affine,
.points_make_affine = ec_GFp_simple_points_make_affine,
.mul_generator_ct = ec_GFp_simple_mul_generator_ct,
.mul_single_ct = ec_GFp_simple_mul_single_ct,
.mul_double_nonct = ec_GFp_simple_mul_double_nonct,
.field_mul = ec_GFp_simple_field_mul,
.field_sqr = ec_GFp_simple_field_sqr,
.blind_coordinates = ec_GFp_simple_blind_coordinates,
};
return &ret;
}
/* Most method functions in this file are designed to work with
* non-trivial representations of field elements if necessary
* (see ecp_mont.c): while standard modular addition and subtraction
* are used, the field_mul and field_sqr methods will be used for
* multiplication, and field_encode and field_decode (if defined)
* will be used for converting between representations.
* Functions ec_GFp_simple_points_make_affine() and
* ec_GFp_simple_point_get_affine_coordinates() specifically assume
* that if a non-trivial representation is used, it is a Montgomery
* representation (i.e. 'encoding' means multiplying by some factor R).
*/
int
ec_GFp_simple_group_init(EC_GROUP * group)
{
BN_init(&group->field);
BN_init(&group->a);
BN_init(&group->b);
group->a_is_minus3 = 0;
return 1;
}
void
ec_GFp_simple_group_finish(EC_GROUP * group)
{
BN_free(&group->field);
BN_free(&group->a);
BN_free(&group->b);
}
void
ec_GFp_simple_group_clear_finish(EC_GROUP * group)
{
BN_clear_free(&group->field);
BN_clear_free(&group->a);
BN_clear_free(&group->b);
}
int
ec_GFp_simple_group_copy(EC_GROUP * dest, const EC_GROUP * src)
{
if (!BN_copy(&dest->field, &src->field))
return 0;
if (!BN_copy(&dest->a, &src->a))
return 0;
if (!BN_copy(&dest->b, &src->b))
return 0;
dest->a_is_minus3 = src->a_is_minus3;
return 1;
}
int
ec_GFp_simple_group_set_curve(EC_GROUP * group,
const BIGNUM * p, const BIGNUM * a, const BIGNUM * b, BN_CTX * ctx)
{
int ret = 0;
BN_CTX *new_ctx = NULL;
BIGNUM *tmp_a;
/* p must be a prime > 3 */
if (BN_num_bits(p) <= 2 || !BN_is_odd(p)) {
ECerror(EC_R_INVALID_FIELD);
return 0;
}
if (ctx == NULL) {
ctx = new_ctx = BN_CTX_new();
if (ctx == NULL)
return 0;
}
BN_CTX_start(ctx);
if ((tmp_a = BN_CTX_get(ctx)) == NULL)
goto err;
/* group->field */
if (!BN_copy(&group->field, p))
goto err;
BN_set_negative(&group->field, 0);
/* group->a */
if (!BN_nnmod(tmp_a, a, p, ctx))
goto err;
if (group->meth->field_encode) {
if (!group->meth->field_encode(group, &group->a, tmp_a, ctx))
goto err;
} else if (!BN_copy(&group->a, tmp_a))
goto err;
/* group->b */
if (!BN_nnmod(&group->b, b, p, ctx))
goto err;
if (group->meth->field_encode)
if (!group->meth->field_encode(group, &group->b, &group->b, ctx))
goto err;
/* group->a_is_minus3 */
if (!BN_add_word(tmp_a, 3))
goto err;
group->a_is_minus3 = (0 == BN_cmp(tmp_a, &group->field));
ret = 1;
err:
BN_CTX_end(ctx);
BN_CTX_free(new_ctx);
return ret;
}
int
ec_GFp_simple_group_get_curve(const EC_GROUP * group, BIGNUM * p, BIGNUM * a, BIGNUM * b, BN_CTX * ctx)
{
int ret = 0;
BN_CTX *new_ctx = NULL;
if (p != NULL) {
if (!BN_copy(p, &group->field))
return 0;
}
if (a != NULL || b != NULL) {
if (group->meth->field_decode) {
if (ctx == NULL) {
ctx = new_ctx = BN_CTX_new();
if (ctx == NULL)
return 0;
}
if (a != NULL) {
if (!group->meth->field_decode(group, a, &group->a, ctx))
goto err;
}
if (b != NULL) {
if (!group->meth->field_decode(group, b, &group->b, ctx))
goto err;
}
} else {
if (a != NULL) {
if (!BN_copy(a, &group->a))
goto err;
}
if (b != NULL) {
if (!BN_copy(b, &group->b))
goto err;
}
}
}
ret = 1;
err:
BN_CTX_free(new_ctx);
return ret;
}
int
ec_GFp_simple_group_get_degree(const EC_GROUP * group)
{
return BN_num_bits(&group->field);
}
int
ec_GFp_simple_group_check_discriminant(const EC_GROUP * group, BN_CTX * ctx)
{
int ret = 0;
BIGNUM *a, *b, *order, *tmp_1, *tmp_2;
const BIGNUM *p = &group->field;
BN_CTX *new_ctx = NULL;
if (ctx == NULL) {
ctx = new_ctx = BN_CTX_new();
if (ctx == NULL) {
ECerror(ERR_R_MALLOC_FAILURE);
goto err;
}
}
BN_CTX_start(ctx);
if ((a = BN_CTX_get(ctx)) == NULL)
goto err;
if ((b = BN_CTX_get(ctx)) == NULL)
goto err;
if ((tmp_1 = BN_CTX_get(ctx)) == NULL)
goto err;
if ((tmp_2 = BN_CTX_get(ctx)) == NULL)
goto err;
if ((order = BN_CTX_get(ctx)) == NULL)
goto err;
if (group->meth->field_decode) {
if (!group->meth->field_decode(group, a, &group->a, ctx))
goto err;
if (!group->meth->field_decode(group, b, &group->b, ctx))
goto err;
} else {
if (!BN_copy(a, &group->a))
goto err;
if (!BN_copy(b, &group->b))
goto err;
}
/*
* check the discriminant: y^2 = x^3 + a*x + b is an elliptic curve
* <=> 4*a^3 + 27*b^2 != 0 (mod p) 0 =< a, b < p
*/
if (BN_is_zero(a)) {
if (BN_is_zero(b))
goto err;
} else if (!BN_is_zero(b)) {
if (!BN_mod_sqr(tmp_1, a, p, ctx))
goto err;
if (!BN_mod_mul(tmp_2, tmp_1, a, p, ctx))
goto err;
if (!BN_lshift(tmp_1, tmp_2, 2))
goto err;
/* tmp_1 = 4*a^3 */
if (!BN_mod_sqr(tmp_2, b, p, ctx))
goto err;
if (!BN_mul_word(tmp_2, 27))
goto err;
/* tmp_2 = 27*b^2 */
if (!BN_mod_add(a, tmp_1, tmp_2, p, ctx))
goto err;
if (BN_is_zero(a))
goto err;
}
ret = 1;
err:
if (ctx != NULL)
BN_CTX_end(ctx);
BN_CTX_free(new_ctx);
return ret;
}
int
ec_GFp_simple_point_init(EC_POINT * point)
{
BN_init(&point->X);
BN_init(&point->Y);
BN_init(&point->Z);
point->Z_is_one = 0;
return 1;
}
void
ec_GFp_simple_point_finish(EC_POINT * point)
{
BN_free(&point->X);
BN_free(&point->Y);
BN_free(&point->Z);
}
void
ec_GFp_simple_point_clear_finish(EC_POINT * point)
{
BN_clear_free(&point->X);
BN_clear_free(&point->Y);
BN_clear_free(&point->Z);
point->Z_is_one = 0;
}
int
ec_GFp_simple_point_copy(EC_POINT * dest, const EC_POINT * src)
{
if (!BN_copy(&dest->X, &src->X))
return 0;
if (!BN_copy(&dest->Y, &src->Y))
return 0;
if (!BN_copy(&dest->Z, &src->Z))
return 0;
dest->Z_is_one = src->Z_is_one;
return 1;
}
int
ec_GFp_simple_point_set_to_infinity(const EC_GROUP * group, EC_POINT * point)
{
point->Z_is_one = 0;
BN_zero(&point->Z);
return 1;
}
int
ec_GFp_simple_set_Jprojective_coordinates_GFp(const EC_GROUP * group, EC_POINT * point,
const BIGNUM * x, const BIGNUM * y, const BIGNUM * z, BN_CTX * ctx)
{
BN_CTX *new_ctx = NULL;
int ret = 0;
if (ctx == NULL) {
ctx = new_ctx = BN_CTX_new();
if (ctx == NULL)
return 0;
}
if (x != NULL) {
if (!BN_nnmod(&point->X, x, &group->field, ctx))
goto err;
if (group->meth->field_encode) {
if (!group->meth->field_encode(group, &point->X, &point->X, ctx))
goto err;
}
}
if (y != NULL) {
if (!BN_nnmod(&point->Y, y, &group->field, ctx))
goto err;
if (group->meth->field_encode) {
if (!group->meth->field_encode(group, &point->Y, &point->Y, ctx))
goto err;
}
}
if (z != NULL) {
int Z_is_one;
if (!BN_nnmod(&point->Z, z, &group->field, ctx))
goto err;
Z_is_one = BN_is_one(&point->Z);
if (group->meth->field_encode) {
if (Z_is_one && (group->meth->field_set_to_one != 0)) {
if (!group->meth->field_set_to_one(group, &point->Z, ctx))
goto err;
} else {
if (!group->meth->field_encode(group, &point->Z, &point->Z, ctx))
goto err;
}
}
point->Z_is_one = Z_is_one;
}
ret = 1;
err:
BN_CTX_free(new_ctx);
return ret;
}
int
ec_GFp_simple_get_Jprojective_coordinates_GFp(const EC_GROUP * group, const EC_POINT * point,
BIGNUM * x, BIGNUM * y, BIGNUM * z, BN_CTX * ctx)
{
BN_CTX *new_ctx = NULL;
int ret = 0;
if (group->meth->field_decode != 0) {
if (ctx == NULL) {
ctx = new_ctx = BN_CTX_new();
if (ctx == NULL)
return 0;
}
if (x != NULL) {
if (!group->meth->field_decode(group, x, &point->X, ctx))
goto err;
}
if (y != NULL) {
if (!group->meth->field_decode(group, y, &point->Y, ctx))
goto err;
}
if (z != NULL) {
if (!group->meth->field_decode(group, z, &point->Z, ctx))
goto err;
}
} else {
if (x != NULL) {
if (!BN_copy(x, &point->X))
goto err;
}
if (y != NULL) {
if (!BN_copy(y, &point->Y))
goto err;
}
if (z != NULL) {
if (!BN_copy(z, &point->Z))
goto err;
}
}
ret = 1;
err:
BN_CTX_free(new_ctx);
return ret;
}
int
ec_GFp_simple_point_set_affine_coordinates(const EC_GROUP * group, EC_POINT * point,
const BIGNUM * x, const BIGNUM * y, BN_CTX * ctx)
{
if (x == NULL || y == NULL) {
/* unlike for projective coordinates, we do not tolerate this */
ECerror(ERR_R_PASSED_NULL_PARAMETER);
return 0;
}
return EC_POINT_set_Jprojective_coordinates_GFp(group, point, x, y, BN_value_one(), ctx);
}
int
ec_GFp_simple_point_get_affine_coordinates(const EC_GROUP * group, const EC_POINT * point,
BIGNUM * x, BIGNUM * y, BN_CTX * ctx)
{
BN_CTX *new_ctx = NULL;
BIGNUM *Z, *Z_1, *Z_2, *Z_3;
const BIGNUM *Z_;
int ret = 0;
if (EC_POINT_is_at_infinity(group, point) > 0) {
ECerror(EC_R_POINT_AT_INFINITY);
return 0;
}
if (ctx == NULL) {
ctx = new_ctx = BN_CTX_new();
if (ctx == NULL)
return 0;
}
BN_CTX_start(ctx);
if ((Z = BN_CTX_get(ctx)) == NULL)
goto err;
if ((Z_1 = BN_CTX_get(ctx)) == NULL)
goto err;
if ((Z_2 = BN_CTX_get(ctx)) == NULL)
goto err;
if ((Z_3 = BN_CTX_get(ctx)) == NULL)
goto err;
/* transform (X, Y, Z) into (x, y) := (X/Z^2, Y/Z^3) */
if (group->meth->field_decode) {
if (!group->meth->field_decode(group, Z, &point->Z, ctx))
goto err;
Z_ = Z;
} else {
Z_ = &point->Z;
}
if (BN_is_one(Z_)) {
if (group->meth->field_decode) {
if (x != NULL) {
if (!group->meth->field_decode(group, x, &point->X, ctx))
goto err;
}
if (y != NULL) {
if (!group->meth->field_decode(group, y, &point->Y, ctx))
goto err;
}
} else {
if (x != NULL) {
if (!BN_copy(x, &point->X))
goto err;
}
if (y != NULL) {
if (!BN_copy(y, &point->Y))
goto err;
}
}
} else {
if (!BN_mod_inverse_ct(Z_1, Z_, &group->field, ctx)) {
ECerror(ERR_R_BN_LIB);
goto err;
}
if (group->meth->field_encode == 0) {
/* field_sqr works on standard representation */
if (!group->meth->field_sqr(group, Z_2, Z_1, ctx))
goto err;
} else {
if (!BN_mod_sqr(Z_2, Z_1, &group->field, ctx))
goto err;
}
if (x != NULL) {
/*
* in the Montgomery case, field_mul will cancel out
* Montgomery factor in X:
*/
if (!group->meth->field_mul(group, x, &point->X, Z_2, ctx))
goto err;
}
if (y != NULL) {
if (group->meth->field_encode == 0) {
/* field_mul works on standard representation */
if (!group->meth->field_mul(group, Z_3, Z_2, Z_1, ctx))
goto err;
} else {
if (!BN_mod_mul(Z_3, Z_2, Z_1, &group->field, ctx))
goto err;
}
/*
* in the Montgomery case, field_mul will cancel out
* Montgomery factor in Y:
*/
if (!group->meth->field_mul(group, y, &point->Y, Z_3, ctx))
goto err;
}
}
ret = 1;
err:
BN_CTX_end(ctx);
BN_CTX_free(new_ctx);
return ret;
}
int
ec_GFp_simple_add(const EC_GROUP * group, EC_POINT * r, const EC_POINT * a, const EC_POINT * b, BN_CTX * ctx)
{
int (*field_mul) (const EC_GROUP *, BIGNUM *, const BIGNUM *, const BIGNUM *, BN_CTX *);
int (*field_sqr) (const EC_GROUP *, BIGNUM *, const BIGNUM *, BN_CTX *);
const BIGNUM *p;
BN_CTX *new_ctx = NULL;
BIGNUM *n0, *n1, *n2, *n3, *n4, *n5, *n6;
int ret = 0;
if (a == b)
return EC_POINT_dbl(group, r, a, ctx);
if (EC_POINT_is_at_infinity(group, a) > 0)
return EC_POINT_copy(r, b);
if (EC_POINT_is_at_infinity(group, b) > 0)
return EC_POINT_copy(r, a);
field_mul = group->meth->field_mul;
field_sqr = group->meth->field_sqr;
p = &group->field;
if (ctx == NULL) {
ctx = new_ctx = BN_CTX_new();
if (ctx == NULL)
return 0;
}
BN_CTX_start(ctx);
if ((n0 = BN_CTX_get(ctx)) == NULL)
goto end;
if ((n1 = BN_CTX_get(ctx)) == NULL)
goto end;
if ((n2 = BN_CTX_get(ctx)) == NULL)
goto end;
if ((n3 = BN_CTX_get(ctx)) == NULL)
goto end;
if ((n4 = BN_CTX_get(ctx)) == NULL)
goto end;
if ((n5 = BN_CTX_get(ctx)) == NULL)
goto end;
if ((n6 = BN_CTX_get(ctx)) == NULL)
goto end;
/*
* Note that in this function we must not read components of 'a' or
* 'b' once we have written the corresponding components of 'r'. ('r'
* might be one of 'a' or 'b'.)
*/
/* n1, n2 */
if (b->Z_is_one) {
if (!BN_copy(n1, &a->X))
goto end;
if (!BN_copy(n2, &a->Y))
goto end;
/* n1 = X_a */
/* n2 = Y_a */
} else {
if (!field_sqr(group, n0, &b->Z, ctx))
goto end;
if (!field_mul(group, n1, &a->X, n0, ctx))
goto end;
/* n1 = X_a * Z_b^2 */
if (!field_mul(group, n0, n0, &b->Z, ctx))
goto end;
if (!field_mul(group, n2, &a->Y, n0, ctx))
goto end;
/* n2 = Y_a * Z_b^3 */
}
/* n3, n4 */
if (a->Z_is_one) {
if (!BN_copy(n3, &b->X))
goto end;
if (!BN_copy(n4, &b->Y))
goto end;
/* n3 = X_b */
/* n4 = Y_b */
} else {
if (!field_sqr(group, n0, &a->Z, ctx))
goto end;
if (!field_mul(group, n3, &b->X, n0, ctx))
goto end;
/* n3 = X_b * Z_a^2 */
if (!field_mul(group, n0, n0, &a->Z, ctx))
goto end;
if (!field_mul(group, n4, &b->Y, n0, ctx))
goto end;
/* n4 = Y_b * Z_a^3 */
}
/* n5, n6 */
if (!BN_mod_sub_quick(n5, n1, n3, p))
goto end;
if (!BN_mod_sub_quick(n6, n2, n4, p))
goto end;
/* n5 = n1 - n3 */
/* n6 = n2 - n4 */
if (BN_is_zero(n5)) {
if (BN_is_zero(n6)) {
/* a is the same point as b */
BN_CTX_end(ctx);
ret = EC_POINT_dbl(group, r, a, ctx);
ctx = NULL;
goto end;
} else {
/* a is the inverse of b */
BN_zero(&r->Z);
r->Z_is_one = 0;
ret = 1;
goto end;
}
}
/* 'n7', 'n8' */
if (!BN_mod_add_quick(n1, n1, n3, p))
goto end;
if (!BN_mod_add_quick(n2, n2, n4, p))
goto end;
/* 'n7' = n1 + n3 */
/* 'n8' = n2 + n4 */
/* Z_r */
if (a->Z_is_one && b->Z_is_one) {
if (!BN_copy(&r->Z, n5))
goto end;
} else {
if (a->Z_is_one) {
if (!BN_copy(n0, &b->Z))
goto end;
} else if (b->Z_is_one) {
if (!BN_copy(n0, &a->Z))
goto end;
} else {
if (!field_mul(group, n0, &a->Z, &b->Z, ctx))
goto end;
}
if (!field_mul(group, &r->Z, n0, n5, ctx))
goto end;
}
r->Z_is_one = 0;
/* Z_r = Z_a * Z_b * n5 */
/* X_r */
if (!field_sqr(group, n0, n6, ctx))
goto end;
if (!field_sqr(group, n4, n5, ctx))
goto end;
if (!field_mul(group, n3, n1, n4, ctx))
goto end;
if (!BN_mod_sub_quick(&r->X, n0, n3, p))
goto end;
/* X_r = n6^2 - n5^2 * 'n7' */
/* 'n9' */
if (!BN_mod_lshift1_quick(n0, &r->X, p))
goto end;
if (!BN_mod_sub_quick(n0, n3, n0, p))
goto end;
/* n9 = n5^2 * 'n7' - 2 * X_r */
/* Y_r */
if (!field_mul(group, n0, n0, n6, ctx))
goto end;
if (!field_mul(group, n5, n4, n5, ctx))
goto end; /* now n5 is n5^3 */
if (!field_mul(group, n1, n2, n5, ctx))
goto end;
if (!BN_mod_sub_quick(n0, n0, n1, p))
goto end;
if (BN_is_odd(n0))
if (!BN_add(n0, n0, p))
goto end;
/* now 0 <= n0 < 2*p, and n0 is even */
if (!BN_rshift1(&r->Y, n0))
goto end;
/* Y_r = (n6 * 'n9' - 'n8' * 'n5^3') / 2 */
ret = 1;
end:
if (ctx) /* otherwise we already called BN_CTX_end */
BN_CTX_end(ctx);
BN_CTX_free(new_ctx);
return ret;
}
int
ec_GFp_simple_dbl(const EC_GROUP * group, EC_POINT * r, const EC_POINT * a, BN_CTX * ctx)
{
int (*field_mul) (const EC_GROUP *, BIGNUM *, const BIGNUM *, const BIGNUM *, BN_CTX *);
int (*field_sqr) (const EC_GROUP *, BIGNUM *, const BIGNUM *, BN_CTX *);
const BIGNUM *p;
BN_CTX *new_ctx = NULL;
BIGNUM *n0, *n1, *n2, *n3;
int ret = 0;
if (EC_POINT_is_at_infinity(group, a) > 0) {
BN_zero(&r->Z);
r->Z_is_one = 0;
return 1;
}
field_mul = group->meth->field_mul;
field_sqr = group->meth->field_sqr;
p = &group->field;
if (ctx == NULL) {
ctx = new_ctx = BN_CTX_new();
if (ctx == NULL)
return 0;
}
BN_CTX_start(ctx);
if ((n0 = BN_CTX_get(ctx)) == NULL)
goto err;
if ((n1 = BN_CTX_get(ctx)) == NULL)
goto err;
if ((n2 = BN_CTX_get(ctx)) == NULL)
goto err;
if ((n3 = BN_CTX_get(ctx)) == NULL)
goto err;
/*
* Note that in this function we must not read components of 'a' once
* we have written the corresponding components of 'r'. ('r' might
* the same as 'a'.)
*/
/* n1 */
if (a->Z_is_one) {
if (!field_sqr(group, n0, &a->X, ctx))
goto err;
if (!BN_mod_lshift1_quick(n1, n0, p))
goto err;
if (!BN_mod_add_quick(n0, n0, n1, p))
goto err;
if (!BN_mod_add_quick(n1, n0, &group->a, p))
goto err;
/* n1 = 3 * X_a^2 + a_curve */
} else if (group->a_is_minus3) {
if (!field_sqr(group, n1, &a->Z, ctx))
goto err;
if (!BN_mod_add_quick(n0, &a->X, n1, p))
goto err;
if (!BN_mod_sub_quick(n2, &a->X, n1, p))
goto err;
if (!field_mul(group, n1, n0, n2, ctx))
goto err;
if (!BN_mod_lshift1_quick(n0, n1, p))
goto err;
if (!BN_mod_add_quick(n1, n0, n1, p))
goto err;
/*
* n1 = 3 * (X_a + Z_a^2) * (X_a - Z_a^2) = 3 * X_a^2 - 3 *
* Z_a^4
*/
} else {
if (!field_sqr(group, n0, &a->X, ctx))
goto err;
if (!BN_mod_lshift1_quick(n1, n0, p))
goto err;
if (!BN_mod_add_quick(n0, n0, n1, p))
goto err;
if (!field_sqr(group, n1, &a->Z, ctx))
goto err;
if (!field_sqr(group, n1, n1, ctx))
goto err;
if (!field_mul(group, n1, n1, &group->a, ctx))
goto err;
if (!BN_mod_add_quick(n1, n1, n0, p))
goto err;
/* n1 = 3 * X_a^2 + a_curve * Z_a^4 */
}
/* Z_r */
if (a->Z_is_one) {
if (!BN_copy(n0, &a->Y))
goto err;
} else {
if (!field_mul(group, n0, &a->Y, &a->Z, ctx))
goto err;
}
if (!BN_mod_lshift1_quick(&r->Z, n0, p))
goto err;
r->Z_is_one = 0;
/* Z_r = 2 * Y_a * Z_a */
/* n2 */
if (!field_sqr(group, n3, &a->Y, ctx))
goto err;
if (!field_mul(group, n2, &a->X, n3, ctx))
goto err;
if (!BN_mod_lshift_quick(n2, n2, 2, p))
goto err;
/* n2 = 4 * X_a * Y_a^2 */
/* X_r */
if (!BN_mod_lshift1_quick(n0, n2, p))
goto err;
if (!field_sqr(group, &r->X, n1, ctx))
goto err;
if (!BN_mod_sub_quick(&r->X, &r->X, n0, p))
goto err;
/* X_r = n1^2 - 2 * n2 */
/* n3 */
if (!field_sqr(group, n0, n3, ctx))
goto err;
if (!BN_mod_lshift_quick(n3, n0, 3, p))
goto err;
/* n3 = 8 * Y_a^4 */
/* Y_r */
if (!BN_mod_sub_quick(n0, n2, &r->X, p))
goto err;
if (!field_mul(group, n0, n1, n0, ctx))
goto err;
if (!BN_mod_sub_quick(&r->Y, n0, n3, p))
goto err;
/* Y_r = n1 * (n2 - X_r) - n3 */
ret = 1;
err:
BN_CTX_end(ctx);
BN_CTX_free(new_ctx);
return ret;
}
int
ec_GFp_simple_invert(const EC_GROUP * group, EC_POINT * point, BN_CTX * ctx)
{
if (EC_POINT_is_at_infinity(group, point) > 0 || BN_is_zero(&point->Y))
/* point is its own inverse */
return 1;
return BN_usub(&point->Y, &group->field, &point->Y);
}
int
ec_GFp_simple_is_at_infinity(const EC_GROUP * group, const EC_POINT * point)
{
return BN_is_zero(&point->Z);
}
int
ec_GFp_simple_is_on_curve(const EC_GROUP * group, const EC_POINT * point, BN_CTX * ctx)
{
int (*field_mul) (const EC_GROUP *, BIGNUM *, const BIGNUM *, const BIGNUM *, BN_CTX *);
int (*field_sqr) (const EC_GROUP *, BIGNUM *, const BIGNUM *, BN_CTX *);
const BIGNUM *p;
BN_CTX *new_ctx = NULL;
BIGNUM *rh, *tmp, *Z4, *Z6;
int ret = -1;
if (EC_POINT_is_at_infinity(group, point) > 0)
return 1;
field_mul = group->meth->field_mul;
field_sqr = group->meth->field_sqr;
p = &group->field;
if (ctx == NULL) {
ctx = new_ctx = BN_CTX_new();
if (ctx == NULL)
return -1;
}
BN_CTX_start(ctx);
if ((rh = BN_CTX_get(ctx)) == NULL)
goto err;
if ((tmp = BN_CTX_get(ctx)) == NULL)
goto err;
if ((Z4 = BN_CTX_get(ctx)) == NULL)
goto err;
if ((Z6 = BN_CTX_get(ctx)) == NULL)
goto err;
/*
* We have a curve defined by a Weierstrass equation y^2 = x^3 + a*x
* + b. The point to consider is given in Jacobian projective
* coordinates where (X, Y, Z) represents (x, y) = (X/Z^2, Y/Z^3).
* Substituting this and multiplying by Z^6 transforms the above
* equation into Y^2 = X^3 + a*X*Z^4 + b*Z^6. To test this, we add up
* the right-hand side in 'rh'.
*/
/* rh := X^2 */
if (!field_sqr(group, rh, &point->X, ctx))
goto err;
if (!point->Z_is_one) {
if (!field_sqr(group, tmp, &point->Z, ctx))
goto err;
if (!field_sqr(group, Z4, tmp, ctx))
goto err;
if (!field_mul(group, Z6, Z4, tmp, ctx))
goto err;
/* rh := (rh + a*Z^4)*X */
if (group->a_is_minus3) {
if (!BN_mod_lshift1_quick(tmp, Z4, p))
goto err;
if (!BN_mod_add_quick(tmp, tmp, Z4, p))
goto err;
if (!BN_mod_sub_quick(rh, rh, tmp, p))
goto err;
if (!field_mul(group, rh, rh, &point->X, ctx))
goto err;
} else {
if (!field_mul(group, tmp, Z4, &group->a, ctx))
goto err;
if (!BN_mod_add_quick(rh, rh, tmp, p))
goto err;
if (!field_mul(group, rh, rh, &point->X, ctx))
goto err;
}
/* rh := rh + b*Z^6 */
if (!field_mul(group, tmp, &group->b, Z6, ctx))
goto err;
if (!BN_mod_add_quick(rh, rh, tmp, p))
goto err;
} else {
/* point->Z_is_one */
/* rh := (rh + a)*X */
if (!BN_mod_add_quick(rh, rh, &group->a, p))
goto err;
if (!field_mul(group, rh, rh, &point->X, ctx))
goto err;
/* rh := rh + b */
if (!BN_mod_add_quick(rh, rh, &group->b, p))
goto err;
}
/* 'lh' := Y^2 */
if (!field_sqr(group, tmp, &point->Y, ctx))
goto err;
ret = (0 == BN_ucmp(tmp, rh));
err:
BN_CTX_end(ctx);
BN_CTX_free(new_ctx);
return ret;
}
int
ec_GFp_simple_cmp(const EC_GROUP * group, const EC_POINT * a, const EC_POINT * b, BN_CTX * ctx)
{
/*
* return values: -1 error 0 equal (in affine coordinates) 1
* not equal
*/
int (*field_mul) (const EC_GROUP *, BIGNUM *, const BIGNUM *, const BIGNUM *, BN_CTX *);
int (*field_sqr) (const EC_GROUP *, BIGNUM *, const BIGNUM *, BN_CTX *);
BN_CTX *new_ctx = NULL;
BIGNUM *tmp1, *tmp2, *Za23, *Zb23;
const BIGNUM *tmp1_, *tmp2_;
int ret = -1;
if (EC_POINT_is_at_infinity(group, a) > 0) {
return EC_POINT_is_at_infinity(group, b) > 0 ? 0 : 1;
}
if (EC_POINT_is_at_infinity(group, b) > 0)
return 1;
if (a->Z_is_one && b->Z_is_one) {
return ((BN_cmp(&a->X, &b->X) == 0) && BN_cmp(&a->Y, &b->Y) == 0) ? 0 : 1;
}
field_mul = group->meth->field_mul;
field_sqr = group->meth->field_sqr;
if (ctx == NULL) {
ctx = new_ctx = BN_CTX_new();
if (ctx == NULL)
return -1;
}
BN_CTX_start(ctx);
if ((tmp1 = BN_CTX_get(ctx)) == NULL)
goto end;
if ((tmp2 = BN_CTX_get(ctx)) == NULL)
goto end;
if ((Za23 = BN_CTX_get(ctx)) == NULL)
goto end;
if ((Zb23 = BN_CTX_get(ctx)) == NULL)
goto end;
/*
* We have to decide whether (X_a/Z_a^2, Y_a/Z_a^3) = (X_b/Z_b^2,
* Y_b/Z_b^3), or equivalently, whether (X_a*Z_b^2, Y_a*Z_b^3) =
* (X_b*Z_a^2, Y_b*Z_a^3).
*/
if (!b->Z_is_one) {
if (!field_sqr(group, Zb23, &b->Z, ctx))
goto end;
if (!field_mul(group, tmp1, &a->X, Zb23, ctx))
goto end;
tmp1_ = tmp1;
} else
tmp1_ = &a->X;
if (!a->Z_is_one) {
if (!field_sqr(group, Za23, &a->Z, ctx))
goto end;
if (!field_mul(group, tmp2, &b->X, Za23, ctx))
goto end;
tmp2_ = tmp2;
} else
tmp2_ = &b->X;
/* compare X_a*Z_b^2 with X_b*Z_a^2 */
if (BN_cmp(tmp1_, tmp2_) != 0) {
ret = 1; /* points differ */
goto end;
}
if (!b->Z_is_one) {
if (!field_mul(group, Zb23, Zb23, &b->Z, ctx))
goto end;
if (!field_mul(group, tmp1, &a->Y, Zb23, ctx))
goto end;
/* tmp1_ = tmp1 */
} else
tmp1_ = &a->Y;
if (!a->Z_is_one) {
if (!field_mul(group, Za23, Za23, &a->Z, ctx))
goto end;
if (!field_mul(group, tmp2, &b->Y, Za23, ctx))
goto end;
/* tmp2_ = tmp2 */
} else
tmp2_ = &b->Y;
/* compare Y_a*Z_b^3 with Y_b*Z_a^3 */
if (BN_cmp(tmp1_, tmp2_) != 0) {
ret = 1; /* points differ */
goto end;
}
/* points are equal */
ret = 0;
end:
BN_CTX_end(ctx);
BN_CTX_free(new_ctx);
return ret;
}
int
ec_GFp_simple_make_affine(const EC_GROUP * group, EC_POINT * point, BN_CTX * ctx)
{
BN_CTX *new_ctx = NULL;
BIGNUM *x, *y;
int ret = 0;
if (point->Z_is_one || EC_POINT_is_at_infinity(group, point) > 0)
return 1;
if (ctx == NULL) {
ctx = new_ctx = BN_CTX_new();
if (ctx == NULL)
return 0;
}
BN_CTX_start(ctx);
if ((x = BN_CTX_get(ctx)) == NULL)
goto err;
if ((y = BN_CTX_get(ctx)) == NULL)
goto err;
if (!EC_POINT_get_affine_coordinates_GFp(group, point, x, y, ctx))
goto err;
if (!EC_POINT_set_affine_coordinates_GFp(group, point, x, y, ctx))
goto err;
if (!point->Z_is_one) {
ECerror(ERR_R_INTERNAL_ERROR);
goto err;
}
ret = 1;
err:
BN_CTX_end(ctx);
BN_CTX_free(new_ctx);
return ret;
}
int
ec_GFp_simple_points_make_affine(const EC_GROUP * group, size_t num, EC_POINT * points[], BN_CTX * ctx)
{
BN_CTX *new_ctx = NULL;
BIGNUM *tmp0, *tmp1;
size_t pow2 = 0;
BIGNUM **heap = NULL;
size_t i;
int ret = 0;
if (num == 0)
return 1;
if (ctx == NULL) {
ctx = new_ctx = BN_CTX_new();
if (ctx == NULL)
return 0;
}
BN_CTX_start(ctx);
if ((tmp0 = BN_CTX_get(ctx)) == NULL)
goto err;
if ((tmp1 = BN_CTX_get(ctx)) == NULL)
goto err;
/*
* Before converting the individual points, compute inverses of all Z
* values. Modular inversion is rather slow, but luckily we can do
* with a single explicit inversion, plus about 3 multiplications per
* input value.
*/
pow2 = 1;
while (num > pow2)
pow2 <<= 1;
/*
* Now pow2 is the smallest power of 2 satifsying pow2 >= num. We
* need twice that.
*/
pow2 <<= 1;
heap = reallocarray(NULL, pow2, sizeof heap[0]);
if (heap == NULL)
goto err;
/*
* The array is used as a binary tree, exactly as in heapsort:
*
* heap[1] heap[2] heap[3] heap[4] heap[5]
* heap[6] heap[7] heap[8]heap[9] heap[10]heap[11]
* heap[12]heap[13] heap[14] heap[15]
*
* We put the Z's in the last line; then we set each other node to the
* product of its two child-nodes (where empty or 0 entries are
* treated as ones); then we invert heap[1]; then we invert each
* other node by replacing it by the product of its parent (after
* inversion) and its sibling (before inversion).
*/
heap[0] = NULL;
for (i = pow2 / 2 - 1; i > 0; i--)
heap[i] = NULL;
for (i = 0; i < num; i++)
heap[pow2 / 2 + i] = &points[i]->Z;
for (i = pow2 / 2 + num; i < pow2; i++)
heap[i] = NULL;
/* set each node to the product of its children */
for (i = pow2 / 2 - 1; i > 0; i--) {
heap[i] = BN_new();
if (heap[i] == NULL)
goto err;
if (heap[2 * i] != NULL) {
if ((heap[2 * i + 1] == NULL) || BN_is_zero(heap[2 * i + 1])) {
if (!BN_copy(heap[i], heap[2 * i]))
goto err;
} else {
if (BN_is_zero(heap[2 * i])) {
if (!BN_copy(heap[i], heap[2 * i + 1]))
goto err;
} else {
if (!group->meth->field_mul(group, heap[i],
heap[2 * i], heap[2 * i + 1], ctx))
goto err;
}
}
}
}
/* invert heap[1] */
if (!BN_is_zero(heap[1])) {
if (!BN_mod_inverse_ct(heap[1], heap[1], &group->field, ctx)) {
ECerror(ERR_R_BN_LIB);
goto err;
}
}
if (group->meth->field_encode != 0) {
/*
* in the Montgomery case, we just turned R*H (representing
* H) into 1/(R*H), but we need R*(1/H) (representing
* 1/H); i.e. we have need to multiply by the Montgomery
* factor twice
*/
if (!group->meth->field_encode(group, heap[1], heap[1], ctx))
goto err;
if (!group->meth->field_encode(group, heap[1], heap[1], ctx))
goto err;
}
/* set other heap[i]'s to their inverses */
for (i = 2; i < pow2 / 2 + num; i += 2) {
/* i is even */
if ((heap[i + 1] != NULL) && !BN_is_zero(heap[i + 1])) {
if (!group->meth->field_mul(group, tmp0, heap[i / 2], heap[i + 1], ctx))
goto err;
if (!group->meth->field_mul(group, tmp1, heap[i / 2], heap[i], ctx))
goto err;
if (!BN_copy(heap[i], tmp0))
goto err;
if (!BN_copy(heap[i + 1], tmp1))
goto err;
} else {
if (!BN_copy(heap[i], heap[i / 2]))
goto err;
}
}
/*
* we have replaced all non-zero Z's by their inverses, now fix up
* all the points
*/
for (i = 0; i < num; i++) {
EC_POINT *p = points[i];
if (!BN_is_zero(&p->Z)) {
/* turn (X, Y, 1/Z) into (X/Z^2, Y/Z^3, 1) */
if (!group->meth->field_sqr(group, tmp1, &p->Z, ctx))
goto err;
if (!group->meth->field_mul(group, &p->X, &p->X, tmp1, ctx))
goto err;
if (!group->meth->field_mul(group, tmp1, tmp1, &p->Z, ctx))
goto err;
if (!group->meth->field_mul(group, &p->Y, &p->Y, tmp1, ctx))
goto err;
if (group->meth->field_set_to_one != 0) {
if (!group->meth->field_set_to_one(group, &p->Z, ctx))
goto err;
} else {
if (!BN_one(&p->Z))
goto err;
}
p->Z_is_one = 1;
}
}
ret = 1;
err:
BN_CTX_end(ctx);
BN_CTX_free(new_ctx);
if (heap != NULL) {
/*
* heap[pow2/2] .. heap[pow2-1] have not been allocated
* locally!
*/
for (i = pow2 / 2 - 1; i > 0; i--) {
BN_clear_free(heap[i]);
}
free(heap);
}
return ret;
}
int
ec_GFp_simple_field_mul(const EC_GROUP * group, BIGNUM * r, const BIGNUM * a, const BIGNUM * b, BN_CTX * ctx)
{
return BN_mod_mul(r, a, b, &group->field, ctx);
}
int
ec_GFp_simple_field_sqr(const EC_GROUP * group, BIGNUM * r, const BIGNUM * a, BN_CTX * ctx)
{
return BN_mod_sqr(r, a, &group->field, ctx);
}
/*
* Apply randomization of EC point projective coordinates:
*
* (X, Y, Z) = (lambda^2 * X, lambda^3 * Y, lambda * Z)
*
* where lambda is in the interval [1, group->field).
*/
int
ec_GFp_simple_blind_coordinates(const EC_GROUP *group, EC_POINT *p, BN_CTX *ctx)
{
BIGNUM *lambda = NULL;
BIGNUM *tmp = NULL;
int ret = 0;
BN_CTX_start(ctx);
if ((lambda = BN_CTX_get(ctx)) == NULL)
goto err;
if ((tmp = BN_CTX_get(ctx)) == NULL)
goto err;
/* Generate lambda in [1, group->field - 1] */
if (!bn_rand_interval(lambda, BN_value_one(), &group->field))
goto err;
if (group->meth->field_encode != NULL &&
!group->meth->field_encode(group, lambda, lambda, ctx))
goto err;
/* Z = lambda * Z */
if (!group->meth->field_mul(group, &p->Z, lambda, &p->Z, ctx))
goto err;
/* tmp = lambda^2 */
if (!group->meth->field_sqr(group, tmp, lambda, ctx))
goto err;
/* X = lambda^2 * X */
if (!group->meth->field_mul(group, &p->X, tmp, &p->X, ctx))
goto err;
/* tmp = lambda^3 */
if (!group->meth->field_mul(group, tmp, tmp, lambda, ctx))
goto err;
/* Y = lambda^3 * Y */
if (!group->meth->field_mul(group, &p->Y, tmp, &p->Y, ctx))
goto err;
/* Disable optimized arithmetics after replacing Z by lambda * Z. */
p->Z_is_one = 0;
ret = 1;
err:
BN_CTX_end(ctx);
return ret;
}
#define EC_POINT_BN_set_flags(P, flags) do { \
BN_set_flags(&(P)->X, (flags)); \
BN_set_flags(&(P)->Y, (flags)); \
BN_set_flags(&(P)->Z, (flags)); \
} while(0)
#define EC_POINT_CSWAP(c, a, b, w, t) do { \
if (!BN_swap_ct(c, &(a)->X, &(b)->X, w) || \
!BN_swap_ct(c, &(a)->Y, &(b)->Y, w) || \
!BN_swap_ct(c, &(a)->Z, &(b)->Z, w)) \
goto err; \
t = ((a)->Z_is_one ^ (b)->Z_is_one) & (c); \
(a)->Z_is_one ^= (t); \
(b)->Z_is_one ^= (t); \
} while(0)
/*
* This function computes (in constant time) a point multiplication over the
* EC group.
*
* At a high level, it is Montgomery ladder with conditional swaps.
*
* It performs either a fixed point multiplication
* (scalar * generator)
* when point is NULL, or a variable point multiplication
* (scalar * point)
* when point is not NULL.
*
* scalar should be in the range [0,n) otherwise all constant time bets are off.
*
* NB: This says nothing about EC_POINT_add and EC_POINT_dbl,
* which of course are not constant time themselves.
*
* The product is stored in r.
*
* Returns 1 on success, 0 otherwise.
*/
static int
ec_GFp_simple_mul_ct(const EC_GROUP *group, EC_POINT *r, const BIGNUM *scalar,
const EC_POINT *point, BN_CTX *ctx)
{
int i, cardinality_bits, group_top, kbit, pbit, Z_is_one;
EC_POINT *s = NULL;
BIGNUM *k = NULL;
BIGNUM *lambda = NULL;
BIGNUM *cardinality = NULL;
BN_CTX *new_ctx = NULL;
int ret = 0;
if (ctx == NULL && (ctx = new_ctx = BN_CTX_new()) == NULL)
return 0;
BN_CTX_start(ctx);
if ((s = EC_POINT_new(group)) == NULL)
goto err;
if (point == NULL) {
if (!EC_POINT_copy(s, group->generator))
goto err;
} else {
if (!EC_POINT_copy(s, point))
goto err;
}
EC_POINT_BN_set_flags(s, BN_FLG_CONSTTIME);
if ((cardinality = BN_CTX_get(ctx)) == NULL)
goto err;
if ((lambda = BN_CTX_get(ctx)) == NULL)
goto err;
if ((k = BN_CTX_get(ctx)) == NULL)
goto err;
if (!BN_mul(cardinality, &group->order, &group->cofactor, ctx))
goto err;
/*
* Group cardinalities are often on a word boundary.
* So when we pad the scalar, some timing diff might
* pop if it needs to be expanded due to carries.
* So expand ahead of time.
*/
cardinality_bits = BN_num_bits(cardinality);
group_top = cardinality->top;
if ((bn_wexpand(k, group_top + 2) == NULL) ||
(bn_wexpand(lambda, group_top + 2) == NULL))
goto err;
if (!BN_copy(k, scalar))
goto err;
BN_set_flags(k, BN_FLG_CONSTTIME);
if (BN_num_bits(k) > cardinality_bits || BN_is_negative(k)) {
/*
* This is an unusual input, and we don't guarantee
* constant-timeness
*/
if (!BN_nnmod(k, k, cardinality, ctx))
goto err;
}
if (!BN_add(lambda, k, cardinality))
goto err;
BN_set_flags(lambda, BN_FLG_CONSTTIME);
if (!BN_add(k, lambda, cardinality))
goto err;
/*
* lambda := scalar + cardinality
* k := scalar + 2*cardinality
*/
kbit = BN_is_bit_set(lambda, cardinality_bits);
if (!BN_swap_ct(kbit, k, lambda, group_top + 2))
goto err;
group_top = group->field.top;
if ((bn_wexpand(&s->X, group_top) == NULL) ||
(bn_wexpand(&s->Y, group_top) == NULL) ||
(bn_wexpand(&s->Z, group_top) == NULL) ||
(bn_wexpand(&r->X, group_top) == NULL) ||
(bn_wexpand(&r->Y, group_top) == NULL) ||
(bn_wexpand(&r->Z, group_top) == NULL))
goto err;
/*
* Apply coordinate blinding for EC_POINT if the underlying EC_METHOD
* implements it.
*/
if (!ec_point_blind_coordinates(group, s, ctx))
goto err;
/* top bit is a 1, in a fixed pos */
if (!EC_POINT_copy(r, s))
goto err;
EC_POINT_BN_set_flags(r, BN_FLG_CONSTTIME);
if (!EC_POINT_dbl(group, s, s, ctx))
goto err;
pbit = 0;
/*
* The ladder step, with branches, is
*
* k[i] == 0: S = add(R, S), R = dbl(R)
* k[i] == 1: R = add(S, R), S = dbl(S)
*
* Swapping R, S conditionally on k[i] leaves you with state
*
* k[i] == 0: T, U = R, S
* k[i] == 1: T, U = S, R
*
* Then perform the ECC ops.
*
* U = add(T, U)
* T = dbl(T)
*
* Which leaves you with state
*
* k[i] == 0: U = add(R, S), T = dbl(R)
* k[i] == 1: U = add(S, R), T = dbl(S)
*
* Swapping T, U conditionally on k[i] leaves you with state
*
* k[i] == 0: R, S = T, U
* k[i] == 1: R, S = U, T
*
* Which leaves you with state
*
* k[i] == 0: S = add(R, S), R = dbl(R)
* k[i] == 1: R = add(S, R), S = dbl(S)
*
* So we get the same logic, but instead of a branch it's a
* conditional swap, followed by ECC ops, then another conditional swap.
*
* Optimization: The end of iteration i and start of i-1 looks like
*
* ...
* CSWAP(k[i], R, S)
* ECC
* CSWAP(k[i], R, S)
* (next iteration)
* CSWAP(k[i-1], R, S)
* ECC
* CSWAP(k[i-1], R, S)
* ...
*
* So instead of two contiguous swaps, you can merge the condition
* bits and do a single swap.
*
* k[i] k[i-1] Outcome
* 0 0 No Swap
* 0 1 Swap
* 1 0 Swap
* 1 1 No Swap
*
* This is XOR. pbit tracks the previous bit of k.
*/
for (i = cardinality_bits - 1; i >= 0; i--) {
kbit = BN_is_bit_set(k, i) ^ pbit;
EC_POINT_CSWAP(kbit, r, s, group_top, Z_is_one);
if (!EC_POINT_add(group, s, r, s, ctx))
goto err;
if (!EC_POINT_dbl(group, r, r, ctx))
goto err;
/*
* pbit logic merges this cswap with that of the
* next iteration
*/
pbit ^= kbit;
}
/* one final cswap to move the right value into r */
EC_POINT_CSWAP(pbit, r, s, group_top, Z_is_one);
ret = 1;
err:
EC_POINT_free(s);
if (ctx != NULL)
BN_CTX_end(ctx);
BN_CTX_free(new_ctx);
return ret;
}
#undef EC_POINT_BN_set_flags
#undef EC_POINT_CSWAP
int
ec_GFp_simple_mul_generator_ct(const EC_GROUP *group, EC_POINT *r,
const BIGNUM *scalar, BN_CTX *ctx)
{
return ec_GFp_simple_mul_ct(group, r, scalar, NULL, ctx);
}
int
ec_GFp_simple_mul_single_ct(const EC_GROUP *group, EC_POINT *r,
const BIGNUM *scalar, const EC_POINT *point, BN_CTX *ctx)
{
return ec_GFp_simple_mul_ct(group, r, scalar, point, ctx);
}
int
ec_GFp_simple_mul_double_nonct(const EC_GROUP *group, EC_POINT *r,
const BIGNUM *g_scalar, const BIGNUM *p_scalar, const EC_POINT *point,
BN_CTX *ctx)
{
return ec_wNAF_mul(group, r, g_scalar, 1, &point, &p_scalar, ctx);
}
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