Game Activation

I am looking for a way to make the game require an activation code, the same way that Microsoft office or any other program similar to it does. After having done a fair bit of research, i was unable to come to the conclusion of a descent solution. I did, however, figure out that you would need a third party program for this. Any help or suggestions to other programs are appreciated.

You could make parts of the game on-line using Photon Cloud or to require a person to register a serial number (embedded with the game package) prior to playing the game.