Packet encryption

Hi,I'm trying to make a simple L2 bot, but i got stuck in begginning - in the packet encryption. I rewrote the l2j login thread sources (those about encryption) but it doesn't work. Has anyone any description of L2 packet encryption. And second question - what Init packet (server packet,nr. 0) means? I guess that it something related with encryption, but in l2j sources that packet content is hardcoded.

Thanks for replies (if any ;) )