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#
# The MIT License (MIT)
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# Copyright (c) 2018 Luis Teixeira
# - copied & modified from https://github.com/vergl4s/ethereum-mnemonic-utils
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import hashlib
import hmac
import struct
from base58 import b58encode_check
from ecdsa.curves import SECP256k1
BIP39_PBKDF2_ROUNDS = 2048
BIP39_SALT_MODIFIER = "mnemonic"
BIP32_PRIVDEV = 0x80000000
BIP32_CURVE = SECP256k1
BIP32_SEED_MODIFIER = b'Bitcoin seed'
# https://github.com/ethereum/EIPs/issues/84#issuecomment-528213145
LEDGER_ETH_DERIVATION_PATH = "m/44'/60'/0'/0"
__all__ = [
'mnemonic_to_bip39seed',
'mnemonic_to_private_key',
]
[docs]def mnemonic_to_bip39seed(mnemonic, passphrase):
""" BIP39 seed from a mnemonic key.
Logic adapted from https://github.com/trezor/python-mnemonic. """
mnemonic = bytes(mnemonic, 'utf8')
salt = bytes(BIP39_SALT_MODIFIER + passphrase, 'utf8')
return hashlib.pbkdf2_hmac('sha512', mnemonic, salt, BIP39_PBKDF2_ROUNDS)
def bip39seed_to_bip32masternode(seed):
""" BIP32 master node derivation from a bip39 seed.
Logic adapted from https://github.com/satoshilabs/slips/blob/master/slip-0010/testvectors.py. """
h = hmac.new(BIP32_SEED_MODIFIER, seed, hashlib.sha512).digest()
key, chain_code = h[:32], h[32:]
return key, chain_code
def derive_public_key(private_key):
""" Public key from a private key.
Logic adapted from https://github.com/satoshilabs/slips/blob/master/slip-0010/testvectors.py. """
Q = int.from_bytes(private_key, byteorder='big') * BIP32_CURVE.generator
xstr = int(Q.x()).to_bytes(32, byteorder='big')
parity = Q.y() & 1
return int(2 + parity).to_bytes(1, byteorder='big') + xstr
def derive_bip32childkey(parent_key, parent_chain_code, i):
""" Derives a child key from an existing key, i is current derivation parameter.
Logic adapted from https://github.com/satoshilabs/slips/blob/master/slip-0010/testvectors.py. """
assert len(parent_key) == 32
assert len(parent_chain_code) == 32
k = parent_chain_code
if (i & BIP32_PRIVDEV) != 0:
key = b'\x00' + parent_key
else:
key = derive_public_key(parent_key)
d = key + struct.pack('>L', i)
while True:
h = hmac.new(k, d, hashlib.sha512).digest()
key, chain_code = h[:32], h[32:]
a = int.from_bytes(key, byteorder='big')
b = int.from_bytes(parent_key, byteorder='big')
key = (a + b) % BIP32_CURVE.order
if a < BIP32_CURVE.order and key != 0:
key = int(key).to_bytes(32, byteorder='big')
break
d = b'\x01' + h[32:] + struct.pack('>L', i)
return key, chain_code
def fingerprint(public_key):
""" BIP32 fingerprint formula, used to get b58 serialized key. """
return hashlib.new('ripemd160', hashlib.sha256(public_key).digest()).digest()[:4]
def b58xprv(parent_fingerprint, private_key, chain, depth, childnr):
""" Private key b58 serialization format. """
raw = (b'\x04\x88\xad\xe4' + bytes(chr(depth), 'utf-8') + parent_fingerprint + int(childnr).to_bytes(
4, byteorder='big') + chain + b'\x00' + private_key)
return b58encode_check(raw)
def b58xpub(parent_fingerprint, public_key, chain, depth, childnr):
""" Public key b58 serialization format. """
raw = (b'\x04\x88\xb2\x1e' + bytes(chr(depth), 'utf-8') + parent_fingerprint + int(childnr).to_bytes(
4, byteorder='big') + chain + public_key)
return b58encode_check(raw)
def parse_derivation_path(str_derivation_path):
""" Parses a derivation path such as "m/44'/60/0'/0" and returns
list of integers for each element in path. """
path = []
if str_derivation_path[0:2] != 'm/':
raise ValueError("Can't recognize derivation path. It should look like \"m/44'/60/0'/0\".")
for i in str_derivation_path.lstrip('m/').split('/'):
if "'" in i:
path.append(BIP32_PRIVDEV + int(i[:-1]))
else:
path.append(int(i))
return path
[docs]def mnemonic_to_private_key(mnemonic, str_derivation_path=LEDGER_ETH_DERIVATION_PATH, passphrase=""):
""" Performs all convertions to get a private key from a mnemonic sentence, including:
BIP39 mnemonic to seed
BIP32 seed to master key
BIP32 child derivation of a path provided
Parameters:
mnemonic -- seed wordlist, usually with 24 words, that is used for ledger wallet backup
str_derivation_path -- string that directs BIP32 key derivation, defaults to path
used by ledger ETH wallet
"""
derivation_path = parse_derivation_path(str_derivation_path)
bip39seed = mnemonic_to_bip39seed(mnemonic, passphrase)
master_private_key, master_chain_code = bip39seed_to_bip32masternode(bip39seed)
private_key, chain_code = master_private_key, master_chain_code
for i in derivation_path:
private_key, chain_code = derive_bip32childkey(private_key, chain_code, i)
return private_key