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/* ec_dh.c - TinyCrypt implementation of EC-DH */
/*
* Copyright (c) 2014, Kenneth MacKay
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
* * Redistributions of source code must retain the above copyright notice,
* this list of conditions and the following disclaimer.
* * 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.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
* AND ANY EXPRESS 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 COPYRIGHT HOLDER OR 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.
*/
/*
* Copyright (C) 2017 by Intel Corporation, All Rights Reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
*
* - Redistributions of source code must retain the above copyright notice,
* this list of conditions and the following disclaimer.
*
* - 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.
*
* - Neither the name of Intel Corporation nor the names of its contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
* AND ANY EXPRESS 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 COPYRIGHT OWNER OR 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.
*/
#include <tinycrypt/constants.h>
#include <tinycrypt/ecc.h>
#include <tinycrypt/ecc_dh.h>
#include <tinycrypt/utils.h>
#include <string.h>
#if default_RNG_defined
static uECC_RNG_Function g_rng_function = &default_CSPRNG;
#else
static uECC_RNG_Function g_rng_function = 0;
#endif
int uECC_make_key_with_d(uint8_t *public_key, uint8_t *private_key,
unsigned int *d, uECC_Curve curve)
{
uECC_word_t _private[NUM_ECC_WORDS];
uECC_word_t _public[NUM_ECC_WORDS * 2];
/* This function is designed for test purposes-only (such as validating NIST
* test vectors) as it uses a provided value for d instead of generating
* it uniformly at random. */
memcpy (_private, d, NUM_ECC_BYTES);
/* Computing public-key from private: */
if (EccPoint_compute_public_key(_public, _private, curve)) {
/* Converting buffers to correct bit order: */
uECC_vli_nativeToBytes(private_key,
BITS_TO_BYTES(curve->num_n_bits),
_private);
uECC_vli_nativeToBytes(public_key,
curve->num_bytes,
_public);
uECC_vli_nativeToBytes(public_key + curve->num_bytes,
curve->num_bytes,
_public + curve->num_words);
/* erasing temporary buffer used to store secret: */
_set_secure(_private, 0, NUM_ECC_BYTES);
return 1;
}
return 0;
}
int uECC_make_key(uint8_t *public_key, uint8_t *private_key, uECC_Curve curve)
{
uECC_word_t _random[NUM_ECC_WORDS * 2];
uECC_word_t _private[NUM_ECC_WORDS];
uECC_word_t _public[NUM_ECC_WORDS * 2];
uECC_word_t tries;
for (tries = 0; tries < uECC_RNG_MAX_TRIES; ++tries) {
/* Generating _private uniformly at random: */
uECC_RNG_Function rng_function = uECC_get_rng();
if (!rng_function ||
!rng_function((uint8_t *)_random, 2 * NUM_ECC_WORDS*uECC_WORD_SIZE)) {
return 0;
}
/* computing modular reduction of _random (see FIPS 186.4 B.4.1): */
uECC_vli_mmod(_private, _random, curve->n, BITS_TO_WORDS(curve->num_n_bits));
/* Computing public-key from private: */
if (EccPoint_compute_public_key(_public, _private, curve)) {
/* Converting buffers to correct bit order: */
uECC_vli_nativeToBytes(private_key,
BITS_TO_BYTES(curve->num_n_bits),
_private);
uECC_vli_nativeToBytes(public_key,
curve->num_bytes,
_public);
uECC_vli_nativeToBytes(public_key + curve->num_bytes,
curve->num_bytes,
_public + curve->num_words);
/* erasing temporary buffer that stored secret: */
_set_secure(_private, 0, NUM_ECC_BYTES);
return 1;
}
}
return 0;
}
int uECC_shared_secret(const uint8_t *public_key, const uint8_t *private_key,
uint8_t *secret, uECC_Curve curve)
{
uECC_word_t _public[NUM_ECC_WORDS * 2];
uECC_word_t _private[NUM_ECC_WORDS];
uECC_word_t tmp[NUM_ECC_WORDS];
uECC_word_t *p2[2] = {_private, tmp};
uECC_word_t *initial_Z = 0;
uECC_word_t carry;
wordcount_t num_words = curve->num_words;
wordcount_t num_bytes = curve->num_bytes;
int r;
/* Converting buffers to correct bit order: */
uECC_vli_bytesToNative(_private,
private_key,
BITS_TO_BYTES(curve->num_n_bits));
uECC_vli_bytesToNative(_public,
public_key,
num_bytes);
uECC_vli_bytesToNative(_public + num_words,
public_key + num_bytes,
num_bytes);
/* Regularize the bitcount for the private key so that attackers cannot use a
* side channel attack to learn the number of leading zeros. */
carry = regularize_k(_private, _private, tmp, curve);
/* If an RNG function was specified, try to get a random initial Z value to
* improve protection against side-channel attacks. */
if (g_rng_function) {
if (!uECC_generate_random_int(p2[carry], curve->p, num_words)) {
r = 0;
goto clear_and_out;
}
initial_Z = p2[carry];
}
EccPoint_mult(_public, _public, p2[!carry], initial_Z, curve->num_n_bits + 1,
curve);
uECC_vli_nativeToBytes(secret, num_bytes, _public);
r = !EccPoint_isZero(_public, curve);
clear_and_out:
/* erasing temporary buffer used to store secret: */
_set_secure(p2, 0, sizeof(p2));
_set_secure(tmp, 0, sizeof(tmp));
_set_secure(_private, 0, sizeof(_private));
return r;
}
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