# Coercion-Resistant Voting in Linear Time via Fully Homomorphic Encryption: Towards a Quantum-Safe Scheme

## TL;DR

This paper introduces a linear-time, quantum-resistant voting tallying method using fully homomorphic encryption, improving efficiency and security in coercion-resistant elections.

## Contribution

It presents a novel linear-time tallying approach for JCJ voting protocol using FHE, enhancing efficiency and post-quantum security without altering the core structure.

## Key findings

- Tallying complexity reduced from quadratic to linear time.
- FHE primitives enable efficient removal of invalid votes.
- Discussion on security and post-quantum implications.

## Abstract

We present an approach for performing the tallying work in the coercion-resistant JCJ voting protocol, introduced by Juels, Catalano, and Jakobsson, in linear time using fully homomorphic encryption (FHE). The suggested enhancement also paves the path towards making JCJ quantum-resistant, while leaving the underlying structure of JCJ intact. The exhaustive, comparison-based approach of JCJ using plaintext equivalence tests leads to a quadratic blow-up in the number of votes, which makes the tallying process rather impractical in realistic settings with a large number of voters. We show how the removal of invalid votes can be done in linear time via a solution based on recent advances in various FHE primitives such as hashing, zero-knowledge proofs of correct decryption, verifiable shuffles and threshold FHE. We conclude by touching upon some of the advantages and challenges of such an approach, followed by a discussion of further security and post-quantum considerations.