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trezor-firmware/trezorlib/tests/support/ckd_public.py

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# This file is part of the Trezor project.
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#
# Copyright (C) 2012-2018 SatoshiLabs and contributors
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#
# This library is free software: you can redistribute it and/or modify
# it under the terms of the GNU Lesser General Public License version 3
# as published by the Free Software Foundation.
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#
# This library is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU Lesser General Public License for more details.
#
# You should have received a copy of the License along with this library.
# If not, see <https://www.gnu.org/licenses/lgpl-3.0.html>.
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import hashlib
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import hmac
import struct
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import ecdsa
from ecdsa.curves import SECP256k1
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from ecdsa.ellipticcurve import INFINITY, Point
from ecdsa.util import number_to_string, string_to_number
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from trezorlib import messages, tools
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def point_to_pubkey(point):
order = SECP256k1.order
x_str = number_to_string(point.x(), order)
y_str = number_to_string(point.y(), order)
vk = x_str + y_str
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return struct.pack("B", (vk[63] & 1) + 2) + vk[0:32] # To compressed key
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def sec_to_public_pair(pubkey):
"""Convert a public key in sec binary format to a public pair."""
x = string_to_number(pubkey[1:33])
sec0 = pubkey[:1]
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if sec0 not in (b"\2", b"\3"):
raise ValueError("Compressed pubkey expected")
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def public_pair_for_x(generator, x, is_even):
curve = generator.curve()
p = curve.p()
alpha = (pow(x, 3, p) + curve.a() * x + curve.b()) % p
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beta = ecdsa.numbertheory.square_root_mod_prime(alpha, p)
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if is_even == bool(beta & 1):
return (x, p - beta)
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):
return bool(n & tools.HARDENED_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):
return tools.public_key_to_bc_address(public_node.public_key, address_type)
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def public_ckd(public_node, n):
if not isinstance(n, list):
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raise ValueError("Parameter must be a list")
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node = messages.HDNodeType()
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node.CopyFrom(public_node)
for i in n:
node.CopyFrom(get_subnode(node, i))
return node
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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 ValueError("Prime derivation not supported")
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# 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 = messages.HDNodeType()
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node_out.depth = node.depth + 1
node_out.child_num = i
node_out.chain_code = I64[32:]
node_out.fingerprint = fingerprint(node.public_key)
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# BIP32 magic converts old public key to new public point
x, y = sec_to_public_pair(node.public_key)
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point = I_left_as_exponent * SECP256k1.generator + Point(
SECP256k1.curve, x, y, SECP256k1.order
)
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if point == INFINITY:
raise ValueError("Point cannot be INFINITY")
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# Convert public point to compressed public key
node_out.public_key = point_to_pubkey(point)
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return node_out
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def serialize(node, version=0x0488B21E):
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s = b""
s += struct.pack(">I", version)
s += struct.pack(">B", node.depth)
s += struct.pack(">I", node.fingerprint)
s += struct.pack(">I", node.child_num)
s += node.chain_code
if node.private_key:
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s += b"\x00" + node.private_key
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else:
s += node.public_key
s += tools.btc_hash(s)[:4]
return tools.b58encode(s)
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def deserialize(xpub):
data = tools.b58decode(xpub, None)
if tools.btc_hash(data[:-4])[:4] != data[-4:]:
raise ValueError("Checksum failed")
node = messages.HDNodeType()
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node.depth = struct.unpack(">B", data[4:5])[0]
node.fingerprint = struct.unpack(">I", data[5:9])[0]
node.child_num = struct.unpack(">I", data[9:13])[0]
node.chain_code = data[13:45]
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key = data[45:-4]
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if key[0] == 0:
node.private_key = key[1:]
else:
node.public_key = key
return node