|Aha, but wait! I thought of a simpler and easier way of determining whether or not a player was really invited, and quickly made the changes.
So I'd like to talk more about these things because I feel that that would be more interesting, but on the other hand giving out all the secrets of my defenses would be stupid.
Oh, what the heck. If you can get around my defenses, at least let me know about it so that I can fix the problem.
The code now just checks to see if there is an invitation message to you, of type party invitation, and encoded with the specified party id. As far as I can tell, there's no way to spoof that, so give it your best shot.