How to keep trial period for my j2ee web application

Question

I have developed one j2ee web application and generated .war file of it. I have to share this war file with clients.

My problem is:

1. I don't want to give .war file for permanent use. Instead of to give it for trial period let's say for 30 days, so that they can know the features of application.
2. How to give trial period logic.
3. If I write logic using DB, they can reinstall the whole war file after one month and everything will start working again.
4. Client can also change the timing of system and then my control will go off.
5. I cannot access internet from application because it will be deployed only on intranet.

Please help me in any possible way of achieving this.

Thanks in advance

Answer 1

You very probably cannot do this perfectly (ever heard about cracked games and rooted phones?).

So it's a matter of making it difficult enough for the user to bypass your license, so that they won't bother.

The basic, simple idea is: - Create a license for each user using your private key, that will contain the license expiry date - Check the license for validity in your application, using a corresponding public key (both integrity and expiry date)

This will make sure the user won't get another month by just reinstalling.

Second simple step would be to write the last seen system time each time you exit the application, then check the system time on startup to make sure user didn't set the clock back (beware of daylight savings time though!).

That might get you covered for the two basic tricks to bypass the trial period. For more motivated users, you'll then need to add in more checks.