Session Hashes

[monkeytooth]

I have no clue what the exact technical term is that I am looking for. However. I am wondering. How would I go about creating a session key? I don't know if any of you are facebook junkies like me but if you are chances are you play mafia wars. What I want to know is A) what is the method called and B) what is the best way to create a similar concept.

 

The concept I am speaking of is there temp session keys I know its a hash of some sort base d on a coupe variables per user jumping into the game. It helps them keep people from using bots on their game.

 

What are the steps I should consider in recreating that idea? Any idea's or suggestions? Is it even something I should even put the effort into? I am building up a member style site/store/mall type of site. I want to keep my users logged in for x amount of time which I know I can handle with timestamp based sessions, but I want them to be unique at the same time so noone can spoof one easily at least.