Generating Device-Specific Serial Number

Question

I would like to be able to generate unique serial numbers for each Android device for use in unlocking an application. How could I do this?

EDIT:

The reason is I want to revamp a paid application and provide users who have paid for the old version, which will have a different package name, a way to obtain the full version by downloading an unlockable free version of the application. I would push an update to the old version that would generate and display the code that they could enter to turn the Free version into a fully functional version.

Answer 1

You can use the Android id. This id should be unique to devices, but how it is set depends on the implementation of the device manufacturer.

String deviceId = Secure.getString(context.getContentResolver(),Secure.ANDROID_ID);

The Android Id may change on factory reset of the phone and the user is also able to change it on rooted phones. But if you need an id to identify your user it should be fine.