[bidder33]

this is where Minimum Anti-Collusion Infrastructure https://appliedzkp.github.io/maci/ becomes important, ideally someone should be able to prove they have voted without revealing any information of how they voted, which makes collusion difficult. This is achieved in person with voting booths and making it illegal to photograph your ballot. zero knowledge proofs + sybil resistance mechanisms like brightid or proof of humanity might make it possible online too.