def FromSeed(seed_bytes, key_net_ver=Bip32Conf.KEY_NET_VER.Main()):
""" Create a Bip32 object from the specified seed (e.g. BIP39 seed).
Args:
seed_bytes (bytes) : Seed bytes
key_net_ver (KeyNetVersions object, optional): Key net version object (Bip32 main net version by default)
Returns:
Bip32 object: Bip32 object
Raises:
ValueError: If the seed is too short
Bip32KeyError: If the seed is not suitable for master key generation
"""
# Check seed length
if len(seed_bytes) * 8 < Bip32Const.SEED_MIN_BIT_LEN:
raise ValueError(
"Seed length is too small, it shall be at least %d bit" %
Bip32Const.SEED_MIN_BIT_LEN)
# Compute HMAC
hmac = CryptoUtils.HmacSha512(Bip32Const.MASTER_KEY_HMAC_KEY,
seed_bytes)
# Create BIP32 by splitting the HMAC into two 32-byte sequences
return Bip32(secret=hmac[:32],
chain=hmac[32:],
key_net_ver=key_net_ver)
def __HmacHalves(self, data_bytes):
""" Calculate the HMAC-SHA512 of input data using the chain code as key and returns a tuple of the left and right halves of the HMAC.
Args:
data_bytes (bytes): Data bytes
Returns:
tuple: Left and right halves of the HMAC
"""
# Use chain as HMAC key
hmac = CryptoUtils.HmacSha512(self.m_chain, data_bytes)
return (hmac[:32], hmac[32:])