bip32.py 文件源码

def subkey_secret_exponent_chain_code_pair(
        secret_exponent, chain_code_bytes, i, is_hardened, public_pair=None):
    """
    Yield info for a child node for this node.

    secret_exponent:
        base secret exponent
    chain_code:
        base chain code
    i:
        the index for this node.
    is_hardened:
        use "hardened key derivation". The public version of this node cannot calculate this child.
    public_pair:
        the public_pair for the given secret exponent. If you leave it None, it's calculated for you
        (but then it's slower)

    Returns a pair (new_secret_exponent, new_chain_code)
    """
    i_as_bytes = struct.pack(">L", i)

    if is_hardened:
        data = b'\0' + to_bytes_32(secret_exponent) + i_as_bytes
    else:
        if public_pair is None:
            public_pair = ecdsa.public_pair_for_secret_exponent(ecdsa.generator_secp256k1, secret_exponent)
        sec = public_pair_to_sec(public_pair, compressed=True)
        data = sec + i_as_bytes

    I64 = hmac.HMAC(key=chain_code_bytes, msg=data, digestmod=hashlib.sha512).digest()
    I_left_as_exponent = from_bytes_32(I64[:32])
    if I_left_as_exponent >= ORDER:
        logger.critical(_SUBKEY_VALIDATION_LOG_ERR_FMT)
        raise DerivationError('I_L >= {}'.format(ORDER))
    new_secret_exponent = (I_left_as_exponent + secret_exponent) % ORDER
    if new_secret_exponent == 0:
        logger.critical(_SUBKEY_VALIDATION_LOG_ERR_FMT)
        raise DerivationError('k_{} == 0'.format(i))
    new_chain_code = I64[32:]
    return new_secret_exponent, new_chain_code