def _pad_sig(message, length):
    """ Simplified padding of the message.

    Return message is length bytes and of the format:

    00 01 <FF pading> 00 message
    """
    maxlen = length - 4
    msglen = len(message)
    if msglen > maxlen:
        raise OverflowError('{} byte message > {} message limit'.format(
            msglen, maxlen))
    padlen = length - msglen - 3
    return b''.join([b'\x00\x01', padlen * b'\xff', b'\x00', message.encode
        ('latin1')])
