Encrypting your disks will only keep people from reading them for a century or two. Technology from the future will be able to break today's encryption in a heartbeat, whether it's simple Moore's Law, quantum computing, cryptographic loopholes in today's algorithms, or something else entirely. So if historians from the future care about you, nothing you leave behind will be truly safe.

If you really want to mess with people from the future, do what Beale did, make up a bunch of bogus stuff, and throw it in with all your encrypted documents.