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View Full Version : Create a trial app



scarnavia
07-09-2009, 03:57 PM
Hello
I have an application and i want to create a trial version of it. I need a decent solution. My first approach is to create two values in an key registry, in which to hold application install date and last open application date, to control the backdate of the system. But the values in registry keys can be modified by anyone, so this is not a good solution....
if anyoane can help me, pls do...

ckeyrouz
07-09-2009, 04:02 PM
Create a simple file named license.lic.
When the application is being installed write in it:
installDate=the day date
but before adding it to the license file encrypt it using a certain algorithm of yours that you choose.
and paste the encrypted text inside the license.lic.

When the application starts before doing anything go and check the license.file.
Get the encrypted text, decrypt it and make date comparisons.

scarnavia
07-10-2009, 08:11 AM
Create a simple file named license.lic.
When the application is being installed write in it:
installDate=the day date
but before adding it to the license file encrypt it using a certain algorithm of yours that you choose.
and paste the encrypted text inside the license.lic.

When the application starts before doing anything go and check the license.file.
Get the encrypted text, decrypt it and make date comparisons.

thanks for u're reply....
i don't have much experience with encryption algorithms, so if u can, pls guide me....

scarnavia
07-10-2009, 09:34 AM
and another problem.....

what if, before starting the application, the user change system date (with a valid one), and immediatly after changed back to current date ?

ckeyrouz
07-10-2009, 05:59 PM
First of all I want to know which language you are using so I can help you with an algorithm to encrypt the license file.

It was an idea about the date no problem not a big deal, you can find other solutions than the date.
like when the application starts you start a counter that is equal to the total number of minutes or seconds the application was running.

in the original license.lic you have a counter = 0 and when the application stops you just update the counter in the license this way: counter = counter + totalRunningtime.

and every time you start the application you substract the updated counter value of the license from the total tiral period.

You can find any algorithm.
if you have a database you can save in a certain table and in an encrypted form the total running time.

oracleguy
07-10-2009, 07:12 PM
There are also commercial products that will let you do this FYI. Usually they also give you serial number support for when you sell copies and it lets people convert their trial into a full version after they enter a valid serial number.



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