How to protect Java codes against decompiler? [closed]

Answer 1

The only way that's particularly effective is to offer your program as a web service of some kind, so that the compiled code is never even available on an end-user machine.

The next most effective solution, which is one that is widely used in practice, is to make your program so terrible that no-one wants to use it or spend the time reverse engineering it in the first place. I suspect that when this happens it is typically accidental, however.

Answer 2

1. You can use an obfuscator, like ProGard or Ygard, but it is not too complex to decrypt strings and rename classes, fields and methods.
2. You can encrypt your classes with a private key, and use a custom classloader to decrypt your classes with a public key before loading into memory, but it is not too complex to modify the classloader to save onto a disc all the classes loaded.
3. You can try crash decompilers. JAD is one of the best decompilers but if you add corrupted entries in the constant pools, all products powered by JAD crash. However, some decompilers are still working.

The only way to protect your software, is to deploy it in a SaaS/PaaS.

But keep one's head: most people use a decompiler because they have a technical problem and the documentation is poor or nonexistent. Write a good documentation and use a solid EULA is the better solution.

Answer 3

Software as a Service.