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Anti Reserse Clock

Posted on 2001-08-04
Medium Priority
Last Modified: 2008-02-01
I wanna ask how can I make anti reverse clock .
I have written a demo application expire in specific date,
and I want to prevent program run again, if its expire and the user try to change back the date.

Do any one have good techniques, and what's the method to do that.
I know that any application change the system time send WM_TIMECHANGE to all top windows .
we can capure this message and detect if the system time has been changed.

first, how can I capture this meesage. if I use a background services capture this message. and is this technique usefull.
is there another techniques can I use ..?

Question by:AAB
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LVL 32

Accepted Solution

jhance earned 828 total points
ID: 6351545
The most common technique is to keep a log of the run times of the application and see if you get a new run that is "older" than some prior run.  That way, you know that the clock has been messed with and you can refuse to run or do whatever you want.

I think that your WM_TIMECHANGE method is unreliable since:

1) Your app must be running all the time to catch this.
2) If the system clock is changed via the BIOS setup, you'll never see this change.

Expert Comment

ID: 6354079
I think the best thing to do will be to simply use the windows registry for this.
Make two entries as
First Access
Last access

Based on these two entries you can always check the no of days since last access and also no of days since the installation of your application.
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Expert Comment

ID: 6845275
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Expert Comment

ID: 6871251
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