Is rubber-hose cryptanalysis the concept of extracting info by torture? I guess... I mean, if you're willing to beat someone to get their SSN, you could probably do a lot more harm already just using that info to apply for CCs and loans in their name.
Maybe I'm mistaken or confused here, but in that specific case you could just give any random 9-digit sequence and it would suffice? A non-SSN voter ID would work just as well for a key.
Are people threatening others based on their votes these days?
EDIT: /u/ninjanomnom brought up a good point regarding heads-of-households, which I hadn't thought of before. I suppose some sort of method would be necessary to obfuscate your vote in some situations.
Right so the problem is that you want to be able to verify your vote, but you don't want anyone else to be able to verify your vote. Your SSN is semi-public and lots of people likely already know it (e.g. employer, who is also a prime candidate to try to buy/coerce your vote). But even with a private key, you have to assume you can be coerced into giving it up.
So any system that allows you to verify a vote needs to come not only with a way for you to validate it, but also with deniability built in. Because if it's not then you can a) sell your vote or b) be intimidated into showing how you voted (which may result in a firing/beating if you did it wrong).
There are, I think, one or two ways to achieve this, but it's a non-trivial problem.
Maybe I'm mistaken or confused here, but in that specific case you could just give any random 9-digit sequence and it would suffice? A non-SSN voter ID would work just as well for a key.
Are people threatening others based on their votes these days?
EDIT: /u/ninjanomnom brought up a good point regarding heads-of-households, which I hadn't thought of before. I suppose some sort of method would be necessary to obfuscate your vote in some situations.