is there any paper about how to build a "secure" 30-day trial protection??
because i i don't find any solution for it. you can drop a file on the hd with
the text
"reg at = 21.6.05"
"time to use = 30"

sign it with a private rsa , and check it with the public in your app, but at the end it is always a

compare and jmp problem.

and everybody will patch this jmp...

sorry for this noobish question(is there any crackme for this problem ? )

As long as the trial version has full functionality it is unevitably subject to the "if it runs it can be defeated" theorem.

To have any use of such a discussion you would have to separate the two areas, i.e. first design a trial system that is in theory as hard as possible to break, e.g. using cryptography something like the way you mention above (assuming that those files are generated by the server and not by the program itself of course, since it would then need to contain the private key and hence could be keygenned, and also, to be able to protect from system date resets you should probably have it connect to a server every time it runs, and download a cryptographically signed copy of the current time/date according to the server, in turn based on a high entropy challenge from the client to prevent replay attacks ).

As for patching, you'll just have to use some really hardcore crypter/packer, preferably partly designed by yourself, to have the program be left alone for at least a week or so. But this part is, as mentioned above, ultimately futile.

You could try really compiling 2 versions of the software. One that DOES not have functionality itself. Second which does. The first one goes on the internet for demo. The second one goes directly to the user who has ALREADY paid for it.

The rule here is simple. If the code ain't there, it cannot be cracked. Stop trying to make the saves and prints disabled and then suddenly enabled if properly registed. A typical recepie for failure.

Have Phun

@aim
i don't want sell a trial software, i only thought about protect it...


do you know any nice crack me in this direction ??
except www.download.com ;-)