On Mar 16, 2009, at 6:18 PM, Chris Idou wrote:
Is there any accepted, or preferred or standard way of enforcing a
trial software period for a program on Mac, so that people can't
just delete their preferences or something and start the trial
again? Or does every developer hack their own little solution? (i.e.
write a file to an obscure place).
I'm not sure this is a Cocoa question. But...
I have seen a couple of fairly nice solutions, and lots of really
awful ones. Generally speaking, the awful ones try to go to great
lengths to be sneaky and hide files or other data in places in your
computer they shouldn't be messing with.
The two that I like both involve some simple encryption. They are:
-- Issue an encrypted product key that has to be entered for the
program to run, and embed in the key an expiration date.
-- Store first start-up time (or the expiration time), encrypted,
in the user's .plist for the application, essentially auto-generating
the product key described in the first solution.
In either case, you can implement the code so that the encrypted key
can specify "no expiration", and then use that for paid copies of the
software, having them enter the "no expiration" key to unlock for
permanent use.
I wouldn't waste too much time on trying to prevent unauthorized
access to your program. The harder you try, and the more stringent
the measures, the more likely it is you'll break functionality for
legitimate users in the process, and annoy them with the measures even
if you don't break things. At the same time, any determined user will
have no trouble getting around your attempt to block their access;
usually, simply by downloading a hacked version from a pirate web site
(I hear that's all the rage with iPhone apps these days).
Just do something simple, to encourage the otherwise-honest users to
play by the rules, and leave it at that.
Pete
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