2013-12-16 15:03:38 +00:00
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import struct
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import hmac
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import hashlib
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from ecdsa.util import string_to_number
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from ecdsa.curves import SECP256k1
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2013-12-16 15:26:40 +00:00
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import messages_pb2 as proto
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2013-12-16 15:03:38 +00:00
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PRIME_DERIVATION_FLAG = 0x80000000
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def is_prime(n):
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return (bool)(n & PRIME_DERIVATION_FLAG)
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def hash_160(public_key):
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md = hashlib.new('ripemd160')
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md.update(hashlib.sha256(public_key).digest())
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return md.digest()
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def fingerprint(pubkey):
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return string_to_number(hash_160(pubkey)[:4])
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def get_subnode(node, i):
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# Public Child key derivation (CKD) algorithm of BIP32
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i_as_bytes = struct.pack(">L", i)
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if is_prime(i):
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raise Exception("Prime derivation not supported")
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# Public derivation
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data = node.public_key + i_as_bytes
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I64 = hmac.HMAC(key=node.chain_code, msg=data, digestmod=hashlib.sha512).digest()
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I_left_as_exponent = string_to_number(I64[:32])
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node_out = proto.HDNodeType()
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node_out.version = node.version
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node_out.depth = node.depth + 1
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node_out.child_num = i
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node_out.chain_code = I64[32:]
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node_out.fingerprint = fingerprint(node.public_key)
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# FIXME
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# node_out.public_key = cls._get_pubkey(node_out.private_key)
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# x, y = self.public_pair
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# the_point = I_left_as_exponent * ecdsa.generator_secp256k1 + ecdsa.Point(ecdsa.generator_secp256k1.curve(), x, y, SECP256k1.generator.order())
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return node_out
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