How about encrypt the file. Leave it up to the user to decrypt, and then use as a regular file. Oh, wait- your bosses that be just want this to work in their magical fantasy land, right?

This would be a solution that actually works, there's no crazyness about it or losing sleep about if you did it right or not.

Here's some stuff worth looking over..

• bcrypt
• truecrypt, way overkill, but pretty interesting stuff- mentions steganography, some witchy stuff..