So we've been through this several times now, we release a game (for cheap) and someone hacks it and puts it up on a mirror. We setup Google Alerts for all our apps, so we get told daily who's doing the hacking. So far, we have implemented the licensing service as Google has suggested, our salt is randomly made each time the license is initiated with the unique device ID. We run the check service once, when the application is started for the first time. We then generate a 512 character hash for the key and the stored value that is compared against in SharedPreferences from there on out.
Now, I know that checking once is probably where the application is being blocked. Our bytecode has most likely been looked at and recompiled without the line that initiates the check.
From here, I don't want to obfuscate our code as I have seen it broken before. I want something a little more solid, and I also want to learn how to do this properly. I am more interested in learning than making money at this point since only 2% of people will ever look for a hacked version.
So far, on my own, I have come up with a random number generator that is placed in several startup areas of the game. When initiated (say, 1 out of 50 times) the license is checked. I know this would make it harder to hack because the cracker would have to eliminate each case, compile, eliminate, compile. This method however, is still crackable...so what do you guys suggest? Again, I am really interested in this process of security, so please educate, don't turn this into a discussion on obfuscation or checking periodically based on a timestamp.