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trezor-firmware/trezorlib/ckd_public.py
2013-12-16 17:40:25 +01:00

48 lines
1.3 KiB
Python

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