Re: license key expiring date...
golfdude wrote:
Thanks, Garlington.
Internet time is not an option ( else i can sync up with my server
itself :) ).
I have been thinking of the 2nd option but that is also not full proof
as somebody can read and change that value. But this is much better
than nothing.
(Background: golfdude wants his program to stop working
after an expiration date, even if the system operator sets
the clock back. The "2nd option" calls for the program to
record a time stamp whenever it runs, and to compare it to
the current system time to detect clock diddling. If
golfdude had remembered to INCLUDE SOME CONTEXT with his
reply, this summary would not have been necessary.)
golfdude, you can increase the difficulty by recording
the time stamp in an encrypted form. However, it is more or
less a given that a sufficiently determined cracker will be
able to defeat any protection scheme you come up with[*], if
he chooses to devote sufficient effort to the attack. You
can make his cracking task difficult, but not impossible.
[*] Actually, there *is* a perfect protection scheme,
one hundred percent immune to all cracking attempts: Don't
write the program, and no unlicensed person will be able
to run it.
--
Eric Sosman
esosman@ieee-dot-org.invalid