Possible Duplicate:
How are Software License Keys generated?
I am a beginner in software developement and I would like to know how to implement a protection system on my Java app to protect it against piracy. I know that there's no perfect solution. But i just want to know how protect it. And don't tell me to make it open source,it's impossible in my case :).
Thanks for your time and answers.
As any license enforcement solution can be cracked with a bit of effort, I suggest you don't try to implement copy-protection at all. License management is just inconvenient for your users.
If you are determined to implement copy-protection, you can use an open-source library.
Additionally, you should obfuscate your byte code to make it slightly more difficult to reverse-engineer your application.