###############################################################################
#
# The MIT License (MIT)
#
# 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.
This includes:
- BIP39 mnemonic to seed
- BIP32 seed to master key
- BIP32 child derivation of a path provided
:param mnemonic: seed wordlist, usually with 24 words, that is used for ledger wallet backup
:param str_derivation_path: string that directs BIP32 key derivation, defaults to path used by ledger ETH wallet
:param passphrase: optional passphrase for BIP39 seed generation
"""
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