TRIP: Trustless Coercion-Resistant In-Person Voter Registration

Abstract

Most existing remote electronic voting systems are vulnerable to voter coercion and vote buying. While coercion-resistant voting systems address this challenge, current schemes assume that the voter has access to an untappable, incorruptible device during voter registration. We present TRIP, an in-person voter registration scheme enabling voters to create verifiable and indistinguishable real and fake credentials using an untrusted kiosk inside a privacy booth at a supervised location, e.g., the registrar's office. TRIP ensures the integrity of the voter's real credential while enabling the creation of fake credentials using interactive zero-knowledge proofs between the voter as the verifier and the kiosk as the prover, unbeknownst to the average voter. TRIP ensures that even voters who are under extreme coercion, and cannot leave the booth with a real credential, can delegate their vote to a political party, with the caveat that they must then trust the kiosk. TRIP optimizes the tallying process by limiting the number of credentials a voter can receive and capping the number of votes that a credential can cast per election. We conduct a preliminary usability study among 41 participants at a university and found that 42.5% of participants rated TRIP a B or higher in usability, a promising result for a voter registration scheme that substantially reduces trust in the registrar.