[inlined]

Traditionally, you would sign with the government’s public key so that only they can decrypt it. But ballots are so low entropy that I’d be worried about brute forcing it (maybe some significant nonces can be added?) a solution where you use the block chain signed with certificates held in a central database is just… another case of people pushing blockchain without understanding it

[fulladder]

Nah, not a problem. You generate a random number R and encrypt R || V where V is your vote.

(Or, equivalently, use something like CBC mode with a random i.v.)