mirror of
https://github.com/trezor/trezor-firmware.git
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105 lines
3.4 KiB
C
105 lines
3.4 KiB
C
/**
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* Copyright (c) 2019 Anatolii Kurotych
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*
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* Permission is hereby granted, free of charge, to any person obtaining
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* a copy of this software and associated documentation files (the "Software"),
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* to deal in the Software without restriction, including without limitation
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* the rights to use, copy, modify, merge, publish, distribute, sublicense,
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* and/or sell copies of the Software, and to permit persons to whom the
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* Software is furnished to do so, subject to the following conditions:
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*
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* The above copyright notice and this permission notice shall be included
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* in all copies or substantial portions of the Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
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* OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
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* THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES
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* OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
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* ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
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* OTHER DEALINGS IN THE SOFTWARE.
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*/
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#include "schnorr.h"
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#include "memzero.h"
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// r = H(Q, kpub, m)
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static void calc_r(const curve_point *Q, const uint8_t pub_key[33],
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const uint8_t *msg, const uint32_t msg_len, bignum256 *r) {
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uint8_t Q_compress[33];
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compress_coords(Q, Q_compress);
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SHA256_CTX ctx;
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uint8_t digest[SHA256_DIGEST_LENGTH];
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sha256_Init(&ctx);
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sha256_Update(&ctx, Q_compress, 33);
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sha256_Update(&ctx, pub_key, 33);
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sha256_Update(&ctx, msg, msg_len);
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sha256_Final(&ctx, digest);
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bn_read_be(digest, r);
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}
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// returns 0 if signing succeeded
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int schnorr_sign(const ecdsa_curve *curve, const uint8_t *priv_key,
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const bignum256 *k, const uint8_t *msg, const uint32_t msg_len,
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schnorr_sign_pair *result) {
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bignum256 private_key_scalar;
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bn_read_be(priv_key, &private_key_scalar);
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uint8_t pub_key[33];
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ecdsa_get_public_key33(curve, priv_key, pub_key);
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/* Q = kG */
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curve_point Q;
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scalar_multiply(curve, k, &Q);
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/* r = H(Q, kpub, m) */
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calc_r(&Q, pub_key, msg, msg_len, &result->r);
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/* s = k - r*kpriv mod(order) */
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bignum256 s_temp;
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bn_copy(&result->r, &s_temp);
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bn_multiply(&private_key_scalar, &s_temp, &curve->order);
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bn_subtractmod(k, &s_temp, &result->s, &curve->order);
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memzero(&private_key_scalar, sizeof(private_key_scalar));
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while (bn_is_less(&curve->order, &result->s)) {
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bn_mod(&result->s, &curve->order);
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}
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if (bn_is_zero(&result->s) || bn_is_zero(&result->r)) {
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return 1;
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}
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return 0;
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}
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// returns 0 if verification succeeded
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int schnorr_verify(const ecdsa_curve *curve, const uint8_t *pub_key,
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const uint8_t *msg, const uint32_t msg_len,
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const schnorr_sign_pair *sign) {
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if (msg_len == 0) return 1;
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if (bn_is_zero(&sign->r)) return 2;
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if (bn_is_zero(&sign->s)) return 3;
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if (bn_is_less(&curve->order, &sign->r)) return 4;
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if (bn_is_less(&curve->order, &sign->s)) return 5;
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curve_point pub_key_point;
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if (!ecdsa_read_pubkey(curve, pub_key, &pub_key_point)) {
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return 6;
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}
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// Compute Q = sG + r*kpub
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curve_point sG, Q;
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scalar_multiply(curve, &sign->s, &sG);
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point_multiply(curve, &sign->r, &pub_key_point, &Q);
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point_add(curve, &sG, &Q);
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/* r = H(Q, kpub, m) */
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bignum256 r;
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calc_r(&Q, pub_key, msg, msg_len, &r);
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if (bn_is_equal(&r, &sign->r)) return 0; // success
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return 10;
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}
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