I'm making a small game and would like it to upload/download highscores to/from a central database. I'm using C++ and Qt, so the game will be multi-platform. I would also like to give people the source code so that they can compile the games themselves on platform I don't have access to.
But given the source code, people can easily figure out how to upload fake highscores. Is there any way to make this impossible (or very hard) even with the source code available?