The Login Protocol is the protocol that is used to log a player into RuneScape. This protocol contains information that sets up the encryption for the entire session, using the ISAAC algorithm. The "login block" is encrypted using RSA to prevent third party programs from packet-sniffing the ISAAC cipher keys and breaking the session encryption for the purpose of monitoring, injecting, and generally sniffing packets.
The Game Protocol is the protocol in which game action information is transmitted. The opcodes are encrypted using ISAAC in order to prevent third party programs from tampering with the stream. The game protocol is made up of packets that are structured like so:
The ''opcode'' of a game packet is basically an identifier for the type of game action that the packet represents. The ''size'' of the packet is the amount of bytes that the payload of the packet carries, and the ''payload'' is an array of bytes that holds the actual data (information) of the packet.
A ''fixed-size'' packet is a packet whose payload size does never change, and the size for the specified opcode is already known between both client and server. A ''variable-sized'' packet is a packet whose payload size changes according to the situation of the game session.
