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trezor-firmware/crypto/zkp_bip340.c

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/**
* Copyright (c) SatoshiLabs
*
* 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 <stdbool.h>
#include <string.h>
#include "memzero.h"
#include "sha2.h"
#include "zkp_context.h"
#include "vendor/secp256k1-zkp/include/secp256k1.h"
#include "vendor/secp256k1-zkp/include/secp256k1_extrakeys.h"
#include "vendor/secp256k1-zkp/include/secp256k1_schnorrsig.h"
#include "zkp_bip340.h"
// Initial hash value H for SHA-256 TapTweak:
const uint32_t sha256_initial_taptweak_state[8] = {
0xd129a2f3UL, 0x701c655dUL, 0x6583b6c3UL, 0xb9419727UL,
0x95f4e232UL, 0x94fd54f4UL, 0xa2ae8d85UL, 0x47ca590bUL,
};
// BIP340 Schnorr public key derivation
// private_key_bytes has 32 bytes
// public_key_bytes has 32 bytes
// returns 0 on success
int zkp_bip340_get_public_key(const uint8_t *private_key_bytes,
uint8_t *public_key_bytes) {
int result = 0;
secp256k1_pubkey pubkey = {0};
if (result == 0) {
secp256k1_context *context_writable = zkp_context_acquire_writable();
if (context_writable) {
secp256k1_context_writable_randomize(context_writable);
if (secp256k1_ec_pubkey_create(context_writable, &pubkey,
private_key_bytes) != 1) {
result = -1;
}
zkp_context_release_writable();
} else {
result = -1;
}
}
secp256k1_xonly_pubkey xonly_pubkey = {0};
const secp256k1_context *context_read_only = zkp_context_get_read_only();
if (result == 0) {
if (secp256k1_xonly_pubkey_from_pubkey(context_read_only, &xonly_pubkey,
NULL, &pubkey) != 1) {
result = -1;
}
}
memzero(&pubkey, sizeof(pubkey));
if (result == 0) {
if (secp256k1_xonly_pubkey_serialize(context_read_only, public_key_bytes,
&xonly_pubkey) != 1) {
result = -1;
}
}
memzero(&xonly_pubkey, sizeof(xonly_pubkey));
return result;
}
// BIP340 Schnorr signature signing
// private_key_bytes has 32 bytes
// digest has 32 bytes
// signature_bytes has 64 bytes
// auxiliary_data has 32 bytes or is NULL
// returns 0 on success
int zkp_bip340_sign_digest(const uint8_t *private_key_bytes,
const uint8_t *digest, uint8_t *signature_bytes,
uint8_t *auxiliary_data) {
int result = 0;
secp256k1_keypair keypair = {0};
if (result == 0) {
secp256k1_context *context_writable = zkp_context_acquire_writable();
if (context_writable) {
secp256k1_context_writable_randomize(context_writable);
if (secp256k1_keypair_create(context_writable, &keypair,
private_key_bytes) != 1) {
result = -1;
}
zkp_context_release_writable();
} else {
result = -1;
}
}
if (result == 0) {
secp256k1_context *context_writable = zkp_context_acquire_writable();
if (context_writable) {
secp256k1_context_writable_randomize(context_writable);
if (secp256k1_schnorrsig_sign(context_writable, signature_bytes, digest,
&keypair, auxiliary_data) != 1) {
result = -1;
}
zkp_context_release_writable();
} else {
result = -1;
}
}
memzero(&keypair, sizeof(keypair));
return result;
}
// BIP340 Schnorr signature verification
// public_key_bytes has 32 bytes
// signature_bytes has 64 bytes
// digest has 32 bytes
// returns 0 if verification succeeded
int zkp_bip340_verify_digest(const uint8_t *public_key_bytes,
const uint8_t *signature_bytes,
const uint8_t *digest) {
int result = 0;
secp256k1_xonly_pubkey xonly_pubkey = {0};
const secp256k1_context *context_read_only = zkp_context_get_read_only();
if (result == 0) {
if (secp256k1_xonly_pubkey_parse(context_read_only, &xonly_pubkey,
public_key_bytes) != 1) {
result = 1;
}
}
if (result == 0) {
if (secp256k1_schnorrsig_verify(context_read_only, signature_bytes, digest,
32, &xonly_pubkey) != 1) {
result = 5;
}
}
memzero(&xonly_pubkey, sizeof(xonly_pubkey));
return result;
}
// BIP340 Schnorr public key tweak
// internal_public_key has 32 bytes
// root_hash has 32 bytes or is empty (NULL)
// output_public_key has 32 bytes
// returns 0 on success
int zkp_bip340_tweak_public_key(const uint8_t *internal_public_key,
const uint8_t *root_hash,
uint8_t *output_public_key) {
int result = 0;
uint8_t tweak[SHA256_DIGEST_LENGTH] = {0};
if (result == 0) {
SHA256_CTX ctx = {0};
sha256_Init_ex(&ctx, sha256_initial_taptweak_state, 512);
sha256_Update(&ctx, internal_public_key, 32);
if (root_hash != NULL) {
sha256_Update(&ctx, root_hash, 32);
}
sha256_Final(&ctx, tweak);
}
const secp256k1_context *context_read_only = zkp_context_get_read_only();
secp256k1_xonly_pubkey internal_pubkey = {0};
if (result == 0) {
if (secp256k1_xonly_pubkey_parse(context_read_only, &internal_pubkey,
internal_public_key) != 1) {
result = -1;
}
}
secp256k1_pubkey output_pubkey = {0};
if (result == 0) {
if (secp256k1_xonly_pubkey_tweak_add(context_read_only, &output_pubkey,
&internal_pubkey, tweak) != 1) {
result = -1;
}
}
memzero(tweak, sizeof(tweak));
memzero(&internal_pubkey, sizeof(internal_pubkey));
secp256k1_xonly_pubkey xonly_output_pubkey = {0};
if (result == 0) {
if (secp256k1_xonly_pubkey_from_pubkey(context_read_only,
&xonly_output_pubkey, NULL,
&output_pubkey) != 1) {
result = -1;
}
}
memzero(&output_pubkey, sizeof(output_pubkey));
if (result == 0) {
if (secp256k1_xonly_pubkey_serialize(context_read_only, output_public_key,
&xonly_output_pubkey) != 1) {
result = -1;
}
}
memzero(&xonly_output_pubkey, sizeof(xonly_output_pubkey));
return result;
}
// BIP340 Schnorr private key tweak
// internal_private_key has 32 bytes
// root_hash has 32 bytes or is empty (NULL)
// output_private_key has 32 bytes
// returns 0 on success
int zkp_bip340_tweak_private_key(const uint8_t *internal_private_key,
const uint8_t *root_hash,
uint8_t *output_private_key) {
int result = 0;
secp256k1_keypair keypair = {0};
if (result == 0) {
secp256k1_context *context_writable = zkp_context_acquire_writable();
if (context_writable) {
secp256k1_context_writable_randomize(context_writable);
if (secp256k1_keypair_create(context_writable, &keypair,
internal_private_key) != 1) {
result = -1;
}
zkp_context_release_writable();
} else {
result = -1;
}
}
const secp256k1_context *context_read_only = zkp_context_get_read_only();
secp256k1_xonly_pubkey internal_xonly_pubkey = {0};
if (result == 0) {
if (secp256k1_keypair_xonly_pub(context_read_only, &internal_xonly_pubkey,
NULL, &keypair) != 1) {
result = -1;
}
}
uint8_t internal_public_key[32] = {0};
if (result == 0) {
if (secp256k1_xonly_pubkey_serialize(context_read_only, internal_public_key,
&internal_xonly_pubkey) != 1) {
result = -1;
}
}
memzero(&internal_xonly_pubkey, sizeof(internal_xonly_pubkey));
uint8_t tweak[SHA256_DIGEST_LENGTH] = {0};
if (result == 0) {
SHA256_CTX ctx = {0};
sha256_Init_ex(&ctx, sha256_initial_taptweak_state, 512);
sha256_Update(&ctx, internal_public_key, 32);
if (root_hash != NULL) {
sha256_Update(&ctx, root_hash, 32);
}
sha256_Final(&ctx, tweak);
}
memzero(&internal_public_key, sizeof(internal_public_key));
if (result == 0) {
if (secp256k1_keypair_xonly_tweak_add(context_read_only, &keypair, tweak) !=
1) {
result = -1;
}
}
memzero(tweak, sizeof(tweak));
if (result == 0) {
if (secp256k1_keypair_sec(context_read_only, output_private_key,
&keypair) != 1) {
result = -1;
}
}
memzero(&keypair, sizeof(keypair));
return result;
}