When changing passwords you usually have to type in the old password as well as the new one. They both have to be present in a decrypted form for a short time. If you do a similarity checkup after the user presses change password (where you have both of them in memory), you can tell the user to choose something different. The whole thing needs to be bulletproof and it won't work when the user forgets his/her password, but then the passwords aren't similar anyway. Disclaimer: No security expert, read something similar somewhere once, I guess I'm overseeing something.

How about using a camera pointed to the screen of the compromised computer that does on the fly OCR. You need to create a script which lists content of files as plain text so that it is recognizable, and one that does the reverse. Printing would be an alternative that is really annoying.

What about giving out a "self-destruct key" as is envisioned in different disk level encryption schemes. You just give it to them and they destroy all the data. There is a flaw somewhere probably, maybe cloning the disk would make this irrelevant, as they still have another copy to try it again.

The notion that you shouldn't be able to invoke your vote because somebody could have forced/paid you is inconsistent. Imagine you can vote from home or from any location with internet. What would stop people from going to one guy voting in front of his eyes and getting paid right away?

I must admit I didnt't think about that. It is a well established system so it will be something worth considering. Thanks.

Thanks for the answer. Yes hardware will be a constraint, and the proposed approach would help alevitate that indeed. I'll see to the other aspects on later ocasion, I just wanted to see what the comunity thinks about the security aspect!

For now it is theoretical, I wanted to know about the feasibility. I wanted to try to implement something like this, to learn about stuff and maybe do some non-critical automation with it. I don't expect attacks, but I want to make sure that no stray broadcasts trigger actions in the system. Some basic security is a nice thing too. Well security through obscurity will probably be the case anyway.