Epoque: Practical End-to-End Verifiable Post-Quantum-Secure E-Voting

Abstract—The ultimate goal in modern secure e-voting is

to enable everyone to verify whether the final election

result correctly reflects the votes chosen by the (human)

voters, without exposing how each individual voted. These

fundamental security properties are called end-to-end veri-

fiability and voter privacy. Unfortunately, it turns out to be

very challenging to pursue these properties simultaneously,

especially when the latter must be future-proofed against the

rise of quantum computers. In this work, we show, for the

first time, a practical approach to do this.

We present Epoque, the first end-to-end verifiable, voterprivate, post-quantum-secure homomorphic e-voting protocol. It achieves its properties through the combination

of practical lattice-based cryptographic primitives only, in

a novel way. We formally prove all our security claims

under common trust and hardness assumptions. At the

core of Epoque lies an efficient identity-based encryption

(IBE) scheme with blazingly fast master-key decryption.

It is the component that makes the efficient tallying of

thousands or millions of ballots a practical possibility. In

order to demonstrate its practicality, we fully implemented

it and provide detailed benchmarks; we believe this latter

contribution is of independent interest beyond the specific

e-voting application.