there is a link to the decryt/encrypt guide in my favoirtes list
and look in the exploit section for packet tool
now for the bad news...
you cant change your server.dat to go through a proxy(packet filter) so you cant realy get the first packet to make the 3/4 keys

but best advice read the tutorial untill you understand what its saying
you have to understand what it all means anyway(xor ect...)