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/* Copyright (c) 2018, Google Inc.
*
* Permission to use, copy, modify, and/or distribute this software for any
* purpose with or without fee is hereby granted, provided that the above
* copyright notice and this permission notice appear in all copies.
*
* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
* SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION
* OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
* CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. */
#include <CCryptoBoringSSL_ec.h>
#include <CCryptoBoringSSL_err.h>
#include <CCryptoBoringSSL_mem.h>
#include "internal.h"
#include "../bn/internal.h"
#include "../../internal.h"
int ec_bignum_to_scalar(const EC_GROUP *group, EC_SCALAR *out,
const BIGNUM *in) {
if (!bn_copy_words(out->words, group->order.N.width, in) ||
!bn_less_than_words(out->words, group->order.N.d, group->order.N.width)) {
OPENSSL_PUT_ERROR(EC, EC_R_INVALID_SCALAR);
return 0;
}
return 1;
}
int ec_scalar_equal_vartime(const EC_GROUP *group, const EC_SCALAR *a,
const EC_SCALAR *b) {
return OPENSSL_memcmp(a->words, b->words,
group->order.N.width * sizeof(BN_ULONG)) == 0;
}
int ec_scalar_is_zero(const EC_GROUP *group, const EC_SCALAR *a) {
BN_ULONG mask = 0;
for (int i = 0; i < group->order.N.width; i++) {
mask |= a->words[i];
}
return mask == 0;
}
int ec_random_nonzero_scalar(const EC_GROUP *group, EC_SCALAR *out,
const uint8_t additional_data[32]) {
return bn_rand_range_words(out->words, 1, group->order.N.d,
group->order.N.width, additional_data);
}
void ec_scalar_to_bytes(const EC_GROUP *group, uint8_t *out, size_t *out_len,
const EC_SCALAR *in) {
size_t len = BN_num_bytes(&group->order.N);
bn_words_to_big_endian(out, len, in->words, group->order.N.width);
*out_len = len;
}
int ec_scalar_from_bytes(const EC_GROUP *group, EC_SCALAR *out,
const uint8_t *in, size_t len) {
if (len != BN_num_bytes(&group->order.N)) {
OPENSSL_PUT_ERROR(EC, EC_R_INVALID_SCALAR);
return 0;
}
bn_big_endian_to_words(out->words, group->order.N.width, in, len);
if (!bn_less_than_words(out->words, group->order.N.d, group->order.N.width)) {
OPENSSL_PUT_ERROR(EC, EC_R_INVALID_SCALAR);
return 0;
}
return 1;
}
void ec_scalar_reduce(const EC_GROUP *group, EC_SCALAR *out,
const BN_ULONG *words, size_t num) {
// Convert "from" Montgomery form so the value is reduced modulo the order.
bn_from_montgomery_small(out->words, group->order.N.width, words, num,
&group->order);
// Convert "to" Montgomery form to remove the R^-1 factor added.
ec_scalar_to_montgomery(group, out, out);
}
void ec_scalar_add(const EC_GROUP *group, EC_SCALAR *r, const EC_SCALAR *a,
const EC_SCALAR *b) {
const BIGNUM *order = &group->order.N;
BN_ULONG tmp[EC_MAX_WORDS];
bn_mod_add_words(r->words, a->words, b->words, order->d, tmp, order->width);
OPENSSL_cleanse(tmp, sizeof(tmp));
}
void ec_scalar_sub(const EC_GROUP *group, EC_SCALAR *r, const EC_SCALAR *a,
const EC_SCALAR *b) {
const BIGNUM *order = &group->order.N;
BN_ULONG tmp[EC_MAX_WORDS];
bn_mod_sub_words(r->words, a->words, b->words, order->d, tmp, order->width);
OPENSSL_cleanse(tmp, sizeof(tmp));
}
void ec_scalar_neg(const EC_GROUP *group, EC_SCALAR *r, const EC_SCALAR *a) {
EC_SCALAR zero;
OPENSSL_memset(&zero, 0, sizeof(EC_SCALAR));
ec_scalar_sub(group, r, &zero, a);
}
void ec_scalar_select(const EC_GROUP *group, EC_SCALAR *out, BN_ULONG mask,
const EC_SCALAR *a, const EC_SCALAR *b) {
const BIGNUM *order = &group->order.N;
bn_select_words(out->words, mask, a->words, b->words, order->width);
}
void ec_scalar_to_montgomery(const EC_GROUP *group, EC_SCALAR *r,
const EC_SCALAR *a) {
const BIGNUM *order = &group->order.N;
bn_to_montgomery_small(r->words, a->words, order->width, &group->order);
}
void ec_scalar_from_montgomery(const EC_GROUP *group, EC_SCALAR *r,
const EC_SCALAR *a) {
const BIGNUM *order = &group->order.N;
bn_from_montgomery_small(r->words, order->width, a->words, order->width,
&group->order);
}
void ec_scalar_mul_montgomery(const EC_GROUP *group, EC_SCALAR *r,
const EC_SCALAR *a, const EC_SCALAR *b) {
const BIGNUM *order = &group->order.N;
bn_mod_mul_montgomery_small(r->words, a->words, b->words, order->width,
&group->order);
}
void ec_simple_scalar_inv0_montgomery(const EC_GROUP *group, EC_SCALAR *r,
const EC_SCALAR *a) {
const BIGNUM *order = &group->order.N;
bn_mod_inverse0_prime_mont_small(r->words, a->words, order->width,
&group->order);
}
int ec_simple_scalar_to_montgomery_inv_vartime(const EC_GROUP *group,
EC_SCALAR *r,
const EC_SCALAR *a) {
if (ec_scalar_is_zero(group, a)) {
return 0;
}
// This implementation (in fact) runs in constant time,
// even though for this interface it is not mandatory.
// r = a^-1 in the Montgomery domain. This is
// |ec_scalar_to_montgomery| followed by |ec_scalar_inv0_montgomery|, but
// |ec_scalar_inv0_montgomery| followed by |ec_scalar_from_montgomery| is
// equivalent and slightly more efficient.
ec_scalar_inv0_montgomery(group, r, a);
ec_scalar_from_montgomery(group, r, r);
return 1;
}
void ec_scalar_inv0_montgomery(const EC_GROUP *group, EC_SCALAR *r,
const EC_SCALAR *a) {
group->meth->scalar_inv0_montgomery(group, r, a);
}
int ec_scalar_to_montgomery_inv_vartime(const EC_GROUP *group, EC_SCALAR *r,
const EC_SCALAR *a) {
return group->meth->scalar_to_montgomery_inv_vartime(group, r, a);
}
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