BAVote: Blockchain-Based Electronic Voting System With Privacy and Accountability

Blockchain-based electronic voting systems can achieve voter identity anonymity via cryptographic techniques such as ring signatures and blind signatures. However, fully hiding of voter information mitigates the capability of traceability. Previous mechanisms provide limited traceability, typically by preventing double-voting attacks while compromising anonymity. From the cryptographic point, threshold signature with private accountability seems to offer a balanced solution between privacy and accountability. If directly applying it into blockchain-based electronic voting systems, it needs to fix all voters and each verification has to pre-store all voters' public keys, incurring at least linear-size storage overhead and poor scalability. How to optimize the storage and scalability while guaranteeing both anonymity and traceability remains to be challenging. In this paper, we propose BAVote, an efficient and scalable blockchain-based electronic voting system with anonymity and traceability. It is built on top of a new threshold signature scheme named ConsATS that features a constant-size verification key. ConsATS compresses all voters' public keys into a single verification key, allowing an aggregated ballot to be verified without storing or processing per-voter public keys, thereby reducing on-chain storage overhead and improving scalability in BAVote. The aggregated signature serving as the ballot is encrypted in ConsATS, while BAVote further combines one-time addresses and a commit-reveal mechanism to protect intermediate on-chain data during voting. The corresponding tracing key enables authorized tracer to identify malicious voters during authorized audits. We implement a prototype of BAVote in both a local blockchain environment and the Ethereum Sepolia testnet. The experimental results show that the storage cost of verification keys in our system is reduced by more than 90% and the verification time is 7x faster compared to existing schemes.