If you want to keep stuff private, then do exactly that. User accounts, password authentication, encryption. Those are the things a programmable computer allows. There is the feature of user access control, but I believe this to be a lazy solution because it enforces security through external game mechanics, not programming or even the computer itself.
Well getting hit by a car sucks (I speak from experience (been hit twice in four month (drivers in Germany are terrible (there are too many "()()()()")))) but it isn't irrevertable damage so that's good and it's also good you are getting back into this I hope it works and wish you good luck with your recovery.
Sorry for necroposting (even if it turned out good) I really thought this was new. Apparently I can't read.
Well I'm a decent c/c++ and a a-bit-less-then-decent assembly programmer, but I also understand java and Minecraft modding. If you need help you can ask me but I don't have a great deal of time so you should maybe get someone else in.