def derive_key_pair(seed: Seed) -> t.Tuple[PrivateKey, PublicKey]:
private_key = hashes.sha512half(seed)
public_key = nacl.signing.SigningKey(private_key).verify_key._key[:32] # pylint: disable=protected-access
return (
t.cast(PrivateKey, private_key),
t.cast(PublicKey, KEY_PREFIX + public_key),
)
def derive_private_key(seed: bytes) -> int:
sequence = 0
while True:
buffer = seed + to_bytes(sequence, 4)
private_key = from_bytes(hashes.sha512half(buffer))
if private_key != 0 and private_key < GROUP_ORDER:
return private_key
sequence += 1
def sign_transaction(self, transaction: Transaction) -> SignedTransaction:
result = {
**transaction, 'SigningPubKey': self.public_key.hex().upper()
}
blob = serialize_transaction(result, signing=True)
signature = self.sign(PREFIX_TRANSACTION_SIGNATURE + blob)
result['TxnSignature'] = signature.hex().upper()
blob = serialize_transaction(result)
digest = sha512half(PREFIX_TRANSACTION_ID + blob)
result['hash'] = digest.hex().upper()
return result
def verify(message: bytes, signature: Signature, public_key: PublicKey) -> bool:
digest = hashes.sha512half(message)
# We need `ecdsa` to decompress the public key.
# Would be nice if fastecdsa could do this.
# TODO: Implement it ourselves.
# https://github.com/AntonKueltz/fastecdsa/issues/47
verifying_key = VerifyingKey.from_string(public_key, curves.SECP256k1)
return verifying_key.verify(
signature,
digest,
hashfunc=hashes.IdentityHash,
sigdecode=sigdecode_der,
)
def sign(message: bytes, private_key: PrivateKey) -> Signature:
digest = hashes.sha512half(message)
signing_key = int.from_bytes(private_key, byteorder='big')
r, s = ecdsa.sign(
digest.hex(),
signing_key,
curve=curve.secp256k1,
prehashed=True,
)
# Both (r, s) and (r, -s mod G = G - s) are valid, canonical signatures.
# (r, s) is fully canonical only when s <= G - s.
s_inverse = GROUP_ORDER - s
if s > s_inverse:
s = s_inverse
signature = DEREncoder.encode_signature(r, s)
return t.cast(Signature, signature)
def test_hash_transaction(transaction, blob_hex):
if 'hash' not in transaction:
return
blob = serialization.PREFIX_TRANSACTION_ID + bytes.fromhex(blob_hex)
digest = hashes.sha512half(blob)
assert digest.hex().upper() == transaction['hash']
def test_sha512half():
"""Just a sanity check that we get the same result."""
message = b'test message'
stdlib = hashlib.sha512(message).digest()[:32]
nacl = hashes.sha512half(message)
assert stdlib == nacl
def digest(self) -> bytes:
return hashes.sha512half(self.data)
