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Dogmatron

Demo expiration: How is this done?

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Dogmatron    122
I am wondering how demos of games are able to expire after a certain number of days or times playing. Is this implemented using some kind of DRM software or is this done through a central server-- or a combination of the two? I'm interested in releasing a browser based demo that would expire after a certain amount of time. So maybe a better question is can the same thing be accomplished by only checking with a server, without having anything installed on the user's hard drive? What information could the server use to identify a user since IP addresses can change? Thanks.

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Drakkcon    612
Well, one way to do it would be to create a binary file somewhere where the user wouldn't expect. Then when the program opens for the first time, write the expiration date to the secret file. Every time the program runs, have it check that date. This method is most certainly hackable, but the casual user couldn't do it. You would have to modify the binary file, or turn back the bios time.

I'm only a novice, so it's not like I have done this before. No warranty is provided with this message :)

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Will F    1069
You could use a network card's MAC address. It can be changed, but the average user probably won't know how to do it.

Regardless, it's going to be difficult to do this effectively (if the demo is browser based I can't think of any easy way to do it). If you want to do it by checking with a server, you're going to need to find a way to uniquely identify a user/computer - you're probably going to need to put this on the user's computer.

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Dogmatron    122
Hey, thanks for the replies so far! About the MAC address... I just remembered something a bit interesting about my experience with Ragnarok Online.

I'm running a few computers behind a router, and downloaded the Ragnarok Online demo long ago on one of my computers. After the demo expired, I tried downloading the demo onto another computer on my LAN and was unable to play it after attempting to connect to their servers. So I wonder, would this imply that the Ragnarok Online servers use MAC addresses to authenticate users, and used my router's in this case?

Hmmmm... I don't know if anyone has an answer for this but it is interesting no less.

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