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vince35

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vince35    100
Hi,

I did licensing for my application, but there a major flaw into it. If I give a temporary license, let's say for 1 month, and just look at the system time, the user can simply change its system time in a month and I would have no way to know about it.

I know many apps do it in a smarter way, but I have no clue how. Do you?

Thanks.

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karwosts    840
Though hackers could easily find some kind of way around this, you could maybe do some kind of secret hashed log or registry key containing the timestamp of the last time the program was open. Then you can invalidate your license if the current time is ever less than the last used time (with DST accounted for of course).

Not super secure but a possible solution.

To be honest there's probably not that many people who are willing to mess with their system clocks forever just to get to use one free application :). Unless you actually suspect this is happening I wouldn't stress too much about it.

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vince35    100
I thought about checking it the way you suggest, but I see downsides in invalidating the license. I don't care too much invalidating the license of someone who tried to screw me, but one can have a legit reason to change its system time.

And I'm not super worried about it, but if I am to do it, I might as well do it properly (and learn something at the same time!)

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