public void dump(FileOutputStream out) throws Exception {
        out.write(packet_tag & 0xff);
        out.write(packet_length & 0xff);
        out.write(version & 0xff);
        out.write(key_id & 0xff);
        out.write(s2k & 0xff);
        out.write(cipher_text, 0, packet_length);
    }