ASEV: Anonymous and Scored-Based E-Voting Protocol on Blockchain

E-voting protocols based on the blockchain can ensure secure and fair voting without a trusted third party. Nonetheless, the majority of current blockchain-based voting protocols only permit yes/no voting for a single candidate. This paper proposes an electronic voting protocol utilizing blockchain technology that supports score voting for multiple candidates. Compared with conventional yes/no voting methods, the main challenges of score-based voting are how to ensure that the score assigned for each candidate by a voter is in a defined range, the sum of scores voted by one voter is a predefined constant and the privacy of the voting scores is protected. In our protocol, two types of zero-knowledge proofs, i.e., zero-knowledge proof for set membership (ZKSM) and zero-knowledge sum proof (ZKSP) are used to satisfy the two key requirements of the score constraint. Meanwhile, based on the distributed ElGamal encryption algorithm and Paillier algorithm, we design a novel encryption algorithm to encrypt the ballots, which improves the efficiency of computing the voting results while supporting robustness so that even if some voters abstain or cast invalid votes, the voting results can still be directly computed by each voter without restarting the protocol. The security analysis shows that our voting protocol achieves maximal ballot secrecy, anonymity, eligibility, resistance against multi-voting, robustness, and dispute-freeness. The performance analysis demonstrates the effectiveness and practicality of our voting protocol.