94 lines
2.7 KiB
Python
94 lines
2.7 KiB
Python
import struct
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import hmac
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import hashlib
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import ecdsa
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from ecdsa.util import string_to_number, number_to_string
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from ecdsa.curves import SECP256k1
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from ecdsa.ellipticcurve import Point, INFINITY
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import msqrt
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import tools
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import types_pb2 as proto_types
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PRIME_DERIVATION_FLAG = 0x80000000
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def point_to_pubkey(point):
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order = SECP256k1.order
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x_str = number_to_string(point.x(), order)
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y_str = number_to_string(point.y(), order)
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vk = x_str + y_str
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return chr((ord(vk[63]) & 1) + 2) + vk[0:32] # To compressed key
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def sec_to_public_pair(pubkey):
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"""Convert a public key in sec binary format to a public pair."""
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x = string_to_number(pubkey[1:33])
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sec0 = pubkey[:1]
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if sec0 not in (b'\2', b'\3'):
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raise Exception("Compressed pubkey expected")
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def public_pair_for_x(generator, x, is_even):
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curve = generator.curve()
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p = curve.p()
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alpha = (pow(x, 3, p) + curve.a() * x + curve.b()) % p
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beta = msqrt.modular_sqrt(alpha, p)
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if is_even == bool(beta & 1):
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return (x, p - beta)
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return (x, beta)
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return public_pair_for_x(ecdsa.ecdsa.generator_secp256k1, x, is_even=(sec0 == b'\2'))
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def is_prime(n):
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return (bool)(n & PRIME_DERIVATION_FLAG)
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def fingerprint(pubkey):
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return string_to_number(tools.hash_160(pubkey)[:4])
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def get_address(public_node, address_type):
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return tools.public_key_to_bc_address(public_node.public_key, address_type)
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def public_ckd(public_node, n):
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if not isinstance(n, list):
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raise Exception('Parameter must be a list')
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node = proto_types.HDNodeType()
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node.CopyFrom(public_node)
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for i in n:
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node.CopyFrom(get_subnode(node, i))
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return node
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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_types.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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# BIP32 magic converts old public key to new public point
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x, y = sec_to_public_pair(node.public_key)
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point = I_left_as_exponent * SECP256k1.generator + \
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Point(SECP256k1.curve, x, y, SECP256k1.order)
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if point == INFINITY:
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raise Exception("Point cannot be INFINITY")
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# Convert public point to compressed public key
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node_out.public_key = point_to_pubkey(point)
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return node_out
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