@classmethod
def _decode(cls, packet, key_handler):
    """Decode a version 01 SSH certificate"""
    _ = packet.get_string()
    key_params = key_handler.decode_ssh_public(packet)
    serial = packet.get_uint64()
    cert_type = packet.get_uint32()
    key_id = packet.get_string()
    principals = packet.get_string()
    valid_after = packet.get_uint64()
    valid_before = packet.get_uint64()
    options = packet.get_string()
    extensions = packet.get_string()
    _ = packet.get_string()
    return (key_params, serial, cert_type, key_id, principals, valid_after,
        valid_before, options, extensions)
