That assumption doesn't necessarily hold for a Doctor companion though. He could arrive on an alien planet where the aliens are around our level of technology (and coincidentally speak english!) and it could still work. It could be a little more interesting as the alien could be asking questions about earthlings...
Could be even more interesting than the human companions, who we're meant to believe are both simultaneously brilliant, able to save the universe and solve complex logic problems, but also ask a stream of mundane questions (largely so that unfamiliar concepts can be explained to a varied audience). At least with an alien visitor there would be a reason for asking questions about everyday things. They'd have to be mostly human in appearance though, as the majority of the storylines are centred around human characters (I assume for budgetary reasons) and they'd need to blend in more often than not.
Let me re-state it again --- I did what I did to protect myself legally.
You're making no sense. To protect yourself legally, you are creating a fake file that looks suspicious and draws attention to your actions when you know that, even under threat of imprisonment without trial, you have no way of unlocking the file to prove your innocence? That's like buying a car for cash, filing off all the identifying marks and number plates, destroying all the paperwork and hiding it under a sheet in a garage to "protect yourself legally" - the police are instantly going to think it's stolen and you have left yourself no way to prove that it's not. If you want to protect yourself legally and the file really doesn't contain anything incriminating and you really don't have the means to decrypt it, why not just delete it?
I program, therefore I am.