def __init__(self, secret: bytes, compressed: bool = True):
"""Creates a private key from 32-byte array"""
if len(secret) != 32:
raise ValueError("Secret should be 32-byte array")
if not secp256k1.ec_seckey_verify(secret):
raise ValueError("Secret is not valid (larger then N?)")
self.compressed = compressed
self._secret = secret[:]
def __init__(self, secret, compressed: bool = True, network=NETWORKS["main"]):
"""Creates a private key from 32-byte array"""
if len(secret) != 32:
raise ECError("Secret should be 32-byte array")
if not secp256k1.ec_seckey_verify(secret):
raise ECError("Secret is not valid (larger then N?)")
self.compressed = compressed
self._secret = secret
self.network = network
def taproot_tweak(self, h=b""):
"""Returns a tweaked public key"""
x = self.xonly()
tweak = hashes.tagged_hash("TapTweak", x + h)
if not secp256k1.ec_seckey_verify(tweak):
raise EmbitError("Tweak is too large")
point = secp256k1.ec_pubkey_parse(b"\x02" + x)
pub = secp256k1.ec_pubkey_add(point, tweak)
sec = secp256k1.ec_pubkey_serialize(pub)
return PublicKey.from_xonly(sec[1:33])
def taproot_tweak(self, h=b""):
"""Returns a tweaked private key"""
sec = self.sec()
negate = (sec[0] != 0x02)
x = sec[1:33]
tweak = hashes.tagged_hash("TapTweak", x + h)
if not secp256k1.ec_seckey_verify(tweak):
raise EmbitError("Tweak is too large")
if negate:
secret = secp256k1.ec_privkey_negate(self._secret)
else:
secret = self._secret
res = secp256k1.ec_privkey_add(secret, tweak)
pk = PrivateKey(res)
if pk.sec()[0] == 0x03:
pk = PrivateKey(secp256k1.ec_privkey_negate(res))
return pk
def secp256k1_example():
"""Usage example for secp256k1 usermodule"""
# randomize context from time to time
# - it helps against sidechannel attacks
# secp256k1.context_randomize(os.urandom(32))
# some random secret key
secret = hashlib.sha256(b"secret key").digest()
print("Secret key:", hexlify(secret).decode())
# Makes sense to check if secret key is valid.
# It will be ok in most cases, only if secret > N it will be invalid
if not secp256k1.ec_seckey_verify(secret):
raise ValueError("Secret key is invalid")
# computing corresponding pubkey
pubkey = secp256k1.ec_pubkey_create(secret)
# serialize the pubkey in compressed format
sec = secp256k1.ec_pubkey_serialize(pubkey, secp256k1.EC_COMPRESSED)
print("Public key:", hexlify(sec).decode())
# this is how you parse the pubkey
pubkey = secp256k1.ec_pubkey_parse(sec)
# Signature generation:
# hash of the string "hello"
msg = hashlib.sha256(b"hello").digest()
# signing
sig = secp256k1.ecdsa_sign(msg, secret)
# serialization
der = secp256k1.ecdsa_signature_serialize_der(sig)
print("Signature:", hexlify(der).decode())
# verification
if secp256k1.ecdsa_verify(sig, msg, pubkey):
print("Signature is valid")
else:
printf("Invalid signature")