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trezor-firmware/crypto/rfc6979.c

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/**
* Copyright (c) 2013-2014 Tomas Dzetkulic
* Copyright (c) 2013-2014 Pavol Rusnak
* Copyright (c) 2015 Jochen Hoenicke
*
* Permission is hereby granted, free of charge, to any person obtaining
* a copy of this software and associated documentation files (the "Software"),
* to deal in the Software without restriction, including without limitation
* the rights to use, copy, modify, merge, publish, distribute, sublicense,
* and/or sell copies of the Software, and to permit persons to whom the
* Software is furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included
* in all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
* OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
* THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES
* OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
* ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
* OTHER DEALINGS IN THE SOFTWARE.
*/
#include <assert.h>
#include "hmac_drbg.h"
#include "memzero.h"
#include "rfc6979.h"
void init_rfc6979(const uint8_t *priv_key, const uint8_t *hash,
const ecdsa_curve *curve, rfc6979_state *state) {
if (curve) {
bignum256 hash_bn = {0};
bn_read_be(hash, &hash_bn);
// Make sure hash is partly reduced modulo order
assert(bn_bitcount(&curve->order) >= 256);
bn_mod(&hash_bn, &curve->order);
uint8_t hash_reduced[32] = {0};
bn_write_be(&hash_bn, hash_reduced);
memzero(&hash_bn, sizeof(hash_bn));
hmac_drbg_init(state, priv_key, 32, hash_reduced, 32);
memzero(hash_reduced, sizeof(hash_reduced));
} else {
hmac_drbg_init(state, priv_key, 32, hash, 32);
}
}
// generate next number from deterministic random number generator
void generate_rfc6979(uint8_t rnd[32], rfc6979_state *state) {
hmac_drbg_generate(state, rnd, 32);
}
// generate K in a deterministic way, according to RFC6979
// http://tools.ietf.org/html/rfc6979
void generate_k_rfc6979(bignum256 *k, rfc6979_state *state) {
uint8_t buf[32] = {0};
generate_rfc6979(buf, state);
bn_read_be(buf, k);
memzero(buf, sizeof(buf));
}