A Homomorphic LWE Based E-voting Scheme

In this paper we present a new post-quantum electronic-voting protocol. Our construction is based on LWE fully homomorphic encryption and the protocol is inspired by existing e-voting schemes, in particular Helios. The strengths of our scheme are its simplicity and transparency, since it relies on public homomorphic operations. Furthermore, the use of lattice-based primitives greatly simplifies the proofs of correctness, privacy and verifiability, as no zero-knowledge proof are needed to prove the validity of individual ballots or the correctness of the final election result. The security of our scheme is based on classical SIS/LWE assumptions, which are asymptotically as hard as worst-case lattice problems and relies on the random oracle heuristic. We also propose a new procedure to distribute the decryption task, where each trustee provides an independent proof of correct decryption in the form of a publicly verifiable ciphertext trapdoor. In particular, our protocol requires only two trustees, unlike classical proposals using threshold decryption via Shamir's secret sharing.