All i can say is, if people managed to open official files with a little knowledge and testing, then i'm almost 100% certain they will be able to open / view / steal your files just the same.... unless of course you are the *** of programming now?
Seriously.. people will find a way to get to your files if they really want to, trying to protect them like this is just silly. Be proud that you managed to make files stable enough that people actually WANT to steal them.