visual C#, Protecting windows application using registry

Rather than using the registry, have you considered storing the information on a server which you control? It could be as simple as storing 3 items per install: The computer's MAC address, the install date, and whether or not the install is in trial mode. All you'd need to do is have the software communicate with your server on startup and do a quick legitimacy check. It adds a layer of complexity, yes, but it will be far more reliable than trying to lock down the user's registry entries.

If you do go with the remote legitimacy check, you will need to give some thought on how to deal with clients who are not connected to the internet.

Hi Sheppe,

Well you suggest a quite smart idea, but again problem is with where computer is not connected to internet or computer has limited or restricted internet access.

thanks,

Hi emoreau,

I worked on the suggested method, but again the problem is it did't prevent the re-installation of demo version, however it works for activation thing. I have explained earlier that our demo version is fully featured so if anyone is able to re-install it again and again one will never need to get it activated.

So, by any mean if we could hide something in computer so deeply that only hard disking formatting could erase it. like I have used a trial version of Norton 360, after trial expiry if we try to re-install it never work, cleaning a registry, system restore did't work.

please guide.

>>but again the problem is it did't prevent the re-installation of demo version

it also prevent this because the key in the registry is not created by the installer (so it remains there if you uninstall the application). Your only problem will come from people that might find that key!

One method I used in the past is having the application create an obscurely named file and storing it in a place that a user is unlikely to look, for instance in the Application Data folder for all users. Store the install date in the file and check it against the current date on application startup. If the trial period is over, exit. An uninstall won't remove the file, and the user won't even know it exists. It's a very small file, so you're not doing any harm either.

To expand upon my last comment, using a date as a check could be problematic if the user changes the system date. You may want to limit the number of times a user can run the application, in addition to a date limitation.