Audit-or-Cast: Enforcing Honest Elections with Privacy-Preserving Public Verification

TL;DR

Audit-or-Cast introduces a voting protocol that ensures election transparency and voter privacy simultaneously, even with untrusted clients, by combining tally-hiding aggregation with cast-as-intended verification.

Contribution

It presents ACE, a novel voting protocol that achieves end-to-end verifiability, privacy, and receipt-freeness without relying on trusted clients or revealing vote distributions.

Findings

ACE provides publicly verifiable, tally-hiding election results.

The protocol guarantees strong privacy and receipt-freeness assuming at least one honest tallier.

Formal security proofs validate ACE's properties.

Abstract

Electronic voting systems must balance public verifiability with voter privacy and coercion resistance. Existing cryptographic protocols typically achieve end-to-end verifiability by revealing vote distributions, relying on trusted clients, or enabling transferable receipts - design choices that often compromise trust or privacy in real-world deployments. We present ACE, a voting protocol that reconciles public auditability with strong privacy guarantees. The protocol combines a publicly verifiable, tally-hiding aggregation mechanism with an Audit-or-Cast challenge that enforces cast-as-intended even under untrusted client assumptions. Tallier-side re-randomization eliminates persistent links between voters and public records, yielding information-theoretic receipt-freeness assuming at least one honest tallier. We formalize the security of ACE and show that it simultaneously achieves end-to-end verifiability, publicly tally-hiding results, and strong receipt-freeness without trusted clients.