Amun: Securing E-Voting Against Over-the-Shoulder Coercion

Abstract

In an election where each voter may express $P$ preferences among $M$ possible choices, the Amun protocol allows to secure vote casting against over-the-shoulder adversaries, retaining privacy, fairness, end-to-end verifiability, and correctness. Before the election, each voter receives a ballot containing valid and decoy tokens: only valid tokens contribute in the final tally, but they remain indistinguishable from the decoys. Since the voter is the only one who knows which tokens are valid (without being able to prove it to a coercer), over-the-shoulder attacks are thwarted. We prove the security of the construction under the standard Decisional Diffie Hellman assumption in the random oracle model