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Code Issues Releases Wiki Activity

feat(crypto): Add key tweaking functions to zkp_bip340.c.

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This commit is contained in:
Andrew Kozlik 2021-10-25 18:36:32 +02:00 committed by Andrew Kozlik
parent fd0d1ed871
commit 4a6bd14993
4 changed files with 168 additions and 0 deletions
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9
crypto/sha2.c
View File

@ -677,6 +677,15 @@ void sha256_Init(SHA256_CTX* context) {
context->bitcount = 0;
}
void sha256_Init_ex(SHA256_CTX *context, const uint32_t state[8], uint64_t bitcount) {
if (context == (SHA256_CTX*)0) {
return;
}
MEMCPY_BCOPY(context->state, state, SHA256_DIGEST_LENGTH);
memzero(context->buffer, SHA256_BLOCK_LENGTH);
context->bitcount = bitcount;
}
#ifdef SHA2_UNROLL_TRANSFORM
/* Unrolled SHA-256 round macros: */

1
crypto/sha2.h
View File

@ -74,6 +74,7 @@ char* sha1_Data(const uint8_t*, size_t, char[SHA1_DIGEST_STRING_LENGTH]);
void sha256_Transform(const uint32_t* state_in, const uint32_t* data, uint32_t* state_out);
void sha256_Init(SHA256_CTX *);
void sha256_Init_ex(SHA256_CTX *, const uint32_t state[8], uint64_t bitcount);
void sha256_Update(SHA256_CTX*, const uint8_t*, size_t);
void sha256_Final(SHA256_CTX*, uint8_t[SHA256_DIGEST_LENGTH]);
char* sha256_End(SHA256_CTX*, char[SHA256_DIGEST_STRING_LENGTH]);

152
crypto/zkp_bip340.c
View File

@ -24,6 +24,7 @@
#include <string.h>
#include "memzero.h"
#include "sha2.h"
#include "zkp_context.h"
#include "vendor/secp256k1-zkp/include/secp256k1.h"
@ -32,6 +33,12 @@
#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
@ -157,3 +164,148 @@ int zkp_bip340_verify_digest(const uint8_t *public_key_bytes,
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;
}

6
crypto/zkp_bip340.h
View File

@ -11,5 +11,11 @@ int zkp_bip340_sign_digest(const uint8_t *private_key_bytes,
int zkp_bip340_verify_digest(const uint8_t *public_key_bytes,
const uint8_t *signature_bytes,
const uint8_t *digest);
int zkp_bip340_tweak_public_key(const uint8_t *internal_public_key,
const uint8_t *root_hash,
uint8_t *output_public_key);
int zkp_bip340_tweak_private_key(const uint8_t *internal_private_key,
const uint8_t *root_hash,
uint8_t *output_private_key);
#endif