Privacy-Preserving Dispute Resolution in the Improved Bingo Voting

Dispute resolution mechanisms are important components of voting schemes, deterring a voting authority to change the election outcome as any alteration can be proved by such mechanisms. However, these mechanisms are useless if not triggered by voters, who should not have to choose to either raise a dispute or keep their vote private. Hence, voting schemes should include privacy-preserving dispute resolution. In this work, we advance the formal analysis in the symbolic model of an improved version of the Bingo Voting scheme, whose enhancements include privacy-preserving dispute resolution mechanisms. Most of our analysis of several verification, dispute resolution, and privacy properties is done automatically using ProVerif, which we complement with manual induction proofs as necessary. We find that the scheme meets some properties only if one makes additional trust assumptions to those stated in [6]. For example, we find that dispute resolution is met assuming an honest voting authority. Moreover, our work provides an understanding of privacy-preserving dispute resolution in general, which can be beneficial to similar analyses of other voting schemes.