PSWS: A Private Support-Weighted Sum Protocol for Blockchain-Based E-Voting Systems

Nowadays, e-voting systems are receiving a lot of attention. Voters can cast their votes for the candidates they support on the e-voting system. However, how to reflect the voters’ support level for the candidates in the e-voting system in a fair and privacy-preserving way is still a problem that needs to be solved. This article proposes a private support-weighted sum (PSWS) protocol, which is a fair, and privacy-preserving weighted sum protocol. The PSWS protocol privately calculates the weighted sum of each voter’s support degree for a candidate. After the protocol’s execution, others on the system can only access the weighted sum, without any additional information. The PSWS protocol has two novel characteristics. Firstly, the voting terminal or polling station provides encryption services for ballots immediately after each ballot is cast. All voting information is expressed in ciphertext throughout the weighting and counting processes, until the final result of the weighted vote is passed to the decryption server in ciphertext. This design avoids the disclosure of voter privacy and ballot information, and the ciphertext format also prevents malicious users from cheating or tampering with voter or ballot information during the counting process. Security analysis is conducted to validate security properties. Secondly, our protocol not only achieves the function of privacy-preserving support-weighted voting but also is relatively lightweight and efficient. Finally, the efficiency analysis results of the experiments in terms of calculation show that the protocol meets the requirements applicable to real-world applications. In summary, PSWS can be harmoniously applied to candidate election in blockchain systems.