def child(self, index):
'''Returns the child HDPrivateKey at a particular index.
Raises ValueError for indices >= 0x8000000.
'''
# if index >= 0x80000000, raise a ValueError
if index >= 0x80000000:
raise ValueError('child number should always be less than 2^31')
# data is the SEC compressed and the index in 4 bytes big-endian
data = self.point.sec() + int_to_big_endian(index, 4)
# get hmac_sha512 with chain code, data
h = hmac_sha512(self.chain_code, data)
# the new public point is the current point +
# the first 32 bytes in big endian * G
point = self.point + big_endian_to_int(h[:32]) * G
# chain code is the last 32 bytes
chain_code = h[32:]
# depth is current depth + 1
depth = self.depth + 1
# parent_fingerprint is the fingerprint of this node
parent_fingerprint = self.fingerprint()
# child number is the index
child_number = index
# return the HDPublicKey instance
return HDPublicKey(
point=point,
chain_code=chain_code,
depth=depth,
parent_fingerprint=parent_fingerprint,
child_number=child_number,
testnet=self.testnet,
)
def from_seed(cls, seed, testnet=False):
h = hmac_sha512(b'Bitcoin seed', seed)
private_key = PrivateKey(secret=big_endian_to_int(h[:32]))
chain_code = h[32:]
return cls(
private_key=private_key,
chain_code=chain_code,
testnet=testnet,
)
def from_seed(cls, seed, testnet=False):
# get hmac_sha512 with b'Bitcoin seed' and seed
h = hmac_sha512(b'Bitcoin seed', seed)
# create the private key using the first 32 bytes in big endian
private_key = PrivateKey(secret=big_endian_to_int(h[:32]))
# chaincode is the last 32 bytes
chain_code = h[32:]
# return an instance of the class
return cls(
private_key=private_key,
chain_code=chain_code,
testnet=testnet,
)
def xpub_child(self, index):
if index >= 0x80000000:
raise ValueError('child number should always be less than 2^31')
data = self.point.sec() + int_to_big_endian(index, 4)
h = hmac_sha512(key=self.chain_code, msg=data)
point = self.point + big_endian_to_int(h[:32]) * G
chain_code = h[32:]
depth = self.depth + 1
parent_fingerprint = self.fingerprint()
child_number = index
return HDPublicKey(
point=point,
chain_code=chain_code,
depth=depth,
parent_fingerprint=parent_fingerprint,
child_number=child_number,
testnet=self.testnet,
)
def xprv_child(self, index):
if index >= 0x80000000:
data = int_to_big_endian(self.private_key.secret, 33) + int_to_big_endian(index, 4)
else:
data = self.private_key.point.sec() + int_to_big_endian(index, 4)
h = hmac_sha512(self.chain_code, data)
secret = (big_endian_to_int(h[:32]) + self.private_key.secret) % N
private_key = PrivateKey(secret=secret)
chain_code = h[32:]
depth = self.depth + 1
parent_fingerprint = self.pub.hash160()[:4]
child_number = index
return HDPrivateKey(
private_key=private_key,
chain_code=chain_code,
depth=depth,
parent_fingerprint=parent_fingerprint,
child_number=child_number,
testnet=self.testnet,
)
def child(self, index):
'''Returns the child HDPrivateKey at a particular index.
Hardened children return for indices >= 0x8000000.
'''
# if index >= 0x80000000
if index >= 0x80000000:
# the message data is the private key secret in 33 bytes in
# big-endian and the index in 4 bytes big-endian.
data = int_to_big_endian(self.private_key.secret,
33) + int_to_big_endian(index, 4)
else:
# the message data is the public key compressed SEC
# and the index in 4 bytes big-endian.
data = self.private_key.point.sec() + int_to_big_endian(index, 4)
# get the hmac_sha512 with chain code and data
h = hmac_sha512(self.chain_code, data)
# the new secret is the first 32 bytes as a big-endian integer
# plus the secret mod N
secret = (big_endian_to_int(h[:32]) + self.private_key.secret) % N
# create the PrivateKey object
private_key = PrivateKey(secret=secret)
# the chain code is the last 32 bytes
chain_code = h[32:]
# depth is whatever the current depth + 1
depth = self.depth + 1
# parent_fingerprint is the fingerprint of this node
parent_fingerprint = self.fingerprint()
# child number is the index
child_number = index
# return a new HDPrivateKey instance
return HDPrivateKey(
private_key=private_key,
chain_code=chain_code,
depth=depth,
parent_fingerprint=parent_fingerprint,
child_number=child_number,
testnet=self.testnet,
)