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319 lines
10 KiB
C
319 lines
10 KiB
C
/* ec_dsa.c - TinyCrypt implementation of EC-DSA */
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/*
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* Copyright (c) 2019, Arm Limited (or its affiliates), All Rights Reserved.
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* SPDX-License-Identifier: BSD-3-Clause
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*/
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/* Copyright (c) 2014, Kenneth MacKay
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions are met:
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* * Redistributions of source code must retain the above copyright notice,
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* this list of conditions and the following disclaimer.
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* * Redistributions in binary form must reproduce the above copyright notice,
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* this list of conditions and the following disclaimer in the documentation
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* and/or other materials provided with the distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
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* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
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* LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
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* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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* POSSIBILITY OF SUCH DAMAGE.*/
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/*
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* Copyright (C) 2017 by Intel Corporation, All Rights Reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions are met:
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*
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* - Redistributions of source code must retain the above copyright notice,
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* this list of conditions and the following disclaimer.
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*
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* - Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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*
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* - Neither the name of Intel Corporation nor the names of its contributors
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* may be used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
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* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
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* LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
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* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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* POSSIBILITY OF SUCH DAMAGE.
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*/
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#if !defined(MBEDTLS_CONFIG_FILE)
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#include "mbedtls/config.h"
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#else
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#include MBEDTLS_CONFIG_FILE
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#endif
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#if defined(MBEDTLS_USE_TINYCRYPT)
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#include <tinycrypt/ecc.h>
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#include <tinycrypt/ecc_dsa.h>
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#include "mbedtls/platform_util.h"
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static void bits2int(uECC_word_t *native, const uint8_t *bits,
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unsigned bits_size)
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{
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unsigned num_n_bytes = BITS_TO_BYTES(NUM_ECC_BITS);
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if (bits_size > num_n_bytes) {
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bits_size = num_n_bytes;
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}
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uECC_vli_clear(native);
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uECC_vli_bytesToNative(native, bits, bits_size);
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}
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int uECC_sign_with_k(const uint8_t *private_key, const uint8_t *message_hash,
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unsigned hash_size, uECC_word_t *k, uint8_t *signature)
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{
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uECC_word_t tmp[NUM_ECC_WORDS];
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uECC_word_t s[NUM_ECC_WORDS];
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uECC_word_t p[NUM_ECC_WORDS * 2];
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wordcount_t num_n_words = BITS_TO_WORDS(NUM_ECC_BITS);
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int r = UECC_FAILURE;
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/* Make sure 0 < k < curve_n */
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if (uECC_vli_isZero(k) ||
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uECC_vli_cmp(curve_n, k) != 1) {
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return UECC_FAILURE;
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}
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r = EccPoint_mult_safer(p, curve_G, k);
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if (r != UECC_SUCCESS) {
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return r;
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}
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/* If an RNG function was specified, get a random number
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to prevent side channel analysis of k. */
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if (!uECC_get_rng()) {
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uECC_vli_clear(tmp);
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tmp[0] = 1;
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}
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else if (uECC_generate_random_int(tmp, curve_n, num_n_words) != UECC_SUCCESS) {
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return UECC_FAILURE;
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}
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/* Prevent side channel analysis of uECC_vli_modInv() to determine
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bits of k / the private key by premultiplying by a random number */
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uECC_vli_modMult(k, k, tmp, curve_n); /* k' = rand * k */
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uECC_vli_modInv(k, k, curve_n); /* k = 1 / k' */
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uECC_vli_modMult(k, k, tmp, curve_n); /* k = 1 / k */
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uECC_vli_nativeToBytes(signature, NUM_ECC_BYTES, p); /* store r */
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/* tmp = d: */
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uECC_vli_bytesToNative(tmp, private_key, BITS_TO_BYTES(NUM_ECC_BITS));
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s[num_n_words - 1] = 0;
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uECC_vli_set(s, p);
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uECC_vli_modMult(s, tmp, s, curve_n); /* s = r*d */
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bits2int(tmp, message_hash, hash_size);
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uECC_vli_modAdd(s, tmp, s, curve_n); /* s = e + r*d */
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uECC_vli_modMult(s, s, k, curve_n); /* s = (e + r*d) / k */
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if (uECC_vli_numBits(s) > (bitcount_t)NUM_ECC_BYTES * 8) {
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return UECC_FAILURE;
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}
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uECC_vli_nativeToBytes(signature + NUM_ECC_BYTES, NUM_ECC_BYTES, s);
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return r;
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}
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int uECC_sign(const uint8_t *private_key, const uint8_t *message_hash,
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unsigned hash_size, uint8_t *signature)
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{
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int r;
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uECC_word_t _random[2*NUM_ECC_WORDS];
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uECC_word_t k[NUM_ECC_WORDS];
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uECC_word_t tries;
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volatile const uint8_t *private_key_dup = private_key;
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volatile const uint8_t *message_hash_dup = message_hash;
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volatile unsigned hash_size_dup = hash_size;
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volatile uint8_t *signature_dup = signature;
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for (tries = 0; tries < uECC_RNG_MAX_TRIES; ++tries) {
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/* Generating _random uniformly at random: */
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uECC_RNG_Function rng_function = uECC_get_rng();
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if (!rng_function ||
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rng_function((uint8_t *)_random, 2*NUM_ECC_WORDS*uECC_WORD_SIZE) != 2*NUM_ECC_WORDS*uECC_WORD_SIZE) {
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return UECC_FAILURE;
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}
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// computing k as modular reduction of _random (see FIPS 186.4 B.5.1):
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uECC_vli_mmod(k, _random, curve_n);
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r = uECC_sign_with_k(private_key, message_hash, hash_size, k, signature);
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/* don't keep trying if a fault was detected */
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if (r == UECC_FAULT_DETECTED) {
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mbedtls_platform_memset(signature, 0, 2*NUM_ECC_BYTES);
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return r;
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}
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if (r == UECC_SUCCESS) {
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if (private_key_dup != private_key || message_hash_dup != message_hash ||
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hash_size_dup != hash_size || signature_dup != signature) {
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mbedtls_platform_memset(signature, 0, 2*NUM_ECC_BYTES);
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return UECC_FAULT_DETECTED;
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}
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return UECC_SUCCESS;
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}
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/* else keep trying */
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}
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return UECC_FAILURE;
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}
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static bitcount_t smax(bitcount_t a, bitcount_t b)
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{
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return (a > b ? a : b);
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}
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int uECC_verify(const uint8_t *public_key, const uint8_t *message_hash,
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unsigned hash_size, const uint8_t *signature)
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{
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uECC_word_t u1[NUM_ECC_WORDS], u2[NUM_ECC_WORDS];
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uECC_word_t z[NUM_ECC_WORDS];
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uECC_word_t sum[NUM_ECC_WORDS * 2];
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uECC_word_t rx[NUM_ECC_WORDS];
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uECC_word_t ry[NUM_ECC_WORDS];
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uECC_word_t tx[NUM_ECC_WORDS];
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uECC_word_t ty[NUM_ECC_WORDS];
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uECC_word_t tz[NUM_ECC_WORDS];
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const uECC_word_t *points[4];
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const uECC_word_t *point;
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bitcount_t num_bits;
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bitcount_t i;
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bitcount_t flow_control;
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volatile uECC_word_t diff;
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uECC_word_t _public[NUM_ECC_WORDS * 2];
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uECC_word_t r[NUM_ECC_WORDS], s[NUM_ECC_WORDS];
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wordcount_t num_words = NUM_ECC_WORDS;
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wordcount_t num_n_words = BITS_TO_WORDS(NUM_ECC_BITS);
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rx[num_n_words - 1] = 0;
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r[num_n_words - 1] = 0;
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s[num_n_words - 1] = 0;
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flow_control = 1;
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uECC_vli_bytesToNative(_public, public_key, NUM_ECC_BYTES);
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uECC_vli_bytesToNative(_public + num_words, public_key + NUM_ECC_BYTES,
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NUM_ECC_BYTES);
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uECC_vli_bytesToNative(r, signature, NUM_ECC_BYTES);
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uECC_vli_bytesToNative(s, signature + NUM_ECC_BYTES, NUM_ECC_BYTES);
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/* r, s must not be 0. */
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if (uECC_vli_isZero(r) || uECC_vli_isZero(s)) {
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return UECC_FAILURE;
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}
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/* r, s must be < n. */
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if (uECC_vli_cmp_unsafe(curve_n, r) != 1 ||
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uECC_vli_cmp_unsafe(curve_n, s) != 1) {
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return UECC_FAILURE;
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}
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flow_control++;
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/* Calculate u1 and u2. */
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uECC_vli_modInv(z, s, curve_n); /* z = 1/s */
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u1[num_n_words - 1] = 0;
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bits2int(u1, message_hash, hash_size);
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uECC_vli_modMult(u1, u1, z, curve_n); /* u1 = e/s */
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uECC_vli_modMult(u2, r, z, curve_n); /* u2 = r/s */
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/* Calculate sum = G + Q. */
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uECC_vli_set(sum, _public);
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uECC_vli_set(sum + num_words, _public + num_words);
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uECC_vli_set(tx, curve_G);
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uECC_vli_set(ty, curve_G + num_words);
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uECC_vli_modSub(z, sum, tx, curve_p); /* z = x2 - x1 */
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XYcZ_add(tx, ty, sum, sum + num_words);
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uECC_vli_modInv(z, z, curve_p); /* z = 1/z */
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apply_z(sum, sum + num_words, z);
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flow_control++;
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/* Use Shamir's trick to calculate u1*G + u2*Q */
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points[0] = 0;
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points[1] = curve_G;
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points[2] = _public;
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points[3] = sum;
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num_bits = smax(uECC_vli_numBits(u1),
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uECC_vli_numBits(u2));
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point = points[(!!uECC_vli_testBit(u1, num_bits - 1)) |
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((!!uECC_vli_testBit(u2, num_bits - 1)) << 1)];
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uECC_vli_set(rx, point);
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uECC_vli_set(ry, point + num_words);
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uECC_vli_clear(z);
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z[0] = 1;
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flow_control++;
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for (i = num_bits - 2; i >= 0; --i) {
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uECC_word_t index;
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double_jacobian_default(rx, ry, z);
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index = (!!uECC_vli_testBit(u1, i)) | ((!!uECC_vli_testBit(u2, i)) << 1);
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point = points[index];
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if (point) {
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uECC_vli_set(tx, point);
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uECC_vli_set(ty, point + num_words);
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apply_z(tx, ty, z);
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uECC_vli_modSub(tz, rx, tx, curve_p); /* Z = x2 - x1 */
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XYcZ_add(tx, ty, rx, ry);
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uECC_vli_modMult_fast(z, z, tz);
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}
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flow_control++;
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}
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uECC_vli_modInv(z, z, curve_p); /* Z = 1/Z */
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apply_z(rx, ry, z);
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flow_control++;
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/* v = x1 (mod n) */
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if (uECC_vli_cmp_unsafe(curve_n, rx) != 1) {
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uECC_vli_sub(rx, rx, curve_n);
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}
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/* Accept only if v == r. */
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diff = uECC_vli_equal(rx, r);
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if (diff == 0) {
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flow_control++;
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mbedtls_platform_random_delay();
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/* Re-check the condition and test if the control flow is as expected.
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* 1 (base value) + num_bits - 1 (from the loop) + 5 incrementations.
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*/
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if (diff == 0 && flow_control == (num_bits + 5)) {
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return UECC_SUCCESS;
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}
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else {
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return UECC_FAULT_DETECTED;
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}
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}
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return UECC_FAILURE;
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}
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#endif /* MBEDTLS_USE_TINYCRYPT */
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