Preventing date rollback

[John Simmons]

richard at dataspan.dataspan.UUCP (Richard "Tiger" Melville) writes:

>Many of the software products our company sells rely on a licence file which
>specifies the duration of time the software is licensed for.  The software
>then refuses to run when the period has expired.  It is, however, possible
>to roll back the date on a machine and fool the licence manager software.
>This problem must be solved in order for us to distribute free demo versions
>which work for a specified period only.

>Is there a reliable way to test if the date on a machine has been rolled
>back ?  (System files which have modified dates in the future might do the
>trick.)  As portable a solution as possible is desirable, although we mainly
>run SunOs 4.0.

Couldn't you get your program to check the date fairly regularly when it is
run and write it away somewhere, keeping track of the latest date reached so
far, then refuse to run at any time/date earlier than the latest one stored.
The software may run after the desired date (if unscupulous people fiddle the
machines date ) but it will slowly run out of usable time as the stored date 
gets up to the final die-by date. You could even have a penalty setup such
that it deducts time from the final die-by date if it detects an attempt to
run it at a time before the latest stored time/date.


John Simmons (VK3KJG) Ph. 660 2619	Royal Melbourne Institute of Tech.
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