The account server has to be interoperable with every version of the Conquer Online client there is. This includes the facebook servers (when they existed), mobile servers, etc. Unlike the game server which accepts a version of the game after first contact, the account server has to be able to speak to everybody. When they update their authentication protocol, they don't just update their packets - they create a new packet structure with a new ID. That way, they can continue authenticating their facebook client (for when SRP was introduced, at least), or cleanly reject the old authentication protocol. Off the top of my head, I think

was RC5 and 1060 was a seeded version of RC5 using

.