Abstract: Applying blockchain technology to various application scenarios has become a hot research topic nowadays. The combination of blockchain technology and electronic voting systems can ensure the anonymity of voters and prevent tampering with voting data, making the voting results more fair and trustworthy. On the one hand, it can solve the problem of the central server potentially losing voting data in traditional voting methods. On the other hand, it can protect the privacy of voters’ data and improve the fairness and security of voting. However, there are still issues such as the low efficiency of verifying votes when the number of users increases, and the malicious users casting multiple votes to influence the final voting results. To address these issues, a conditional privacy preservation ring signcryption scheme based on certificateless cryptography is proposed, which can provide secure electronic voting communication while reducing computational costs. By adding tracking tags to signcryption messages, a tracking algorithm is designed to identify malicious voting users from the member list of the ring, enabling the trusted parties to detect and reject malicious votes. Furthermore, batch verification algorithms are adopted to improve the verification efficiency, and smart contracts for vote counting are used to reduce the reliance on third-party institutions. Security analysis shows that the proposed scheme is secure under the random oracle model based on the elliptic curve discrete logarithm and elliptic curve computational Diffie-Hellman hardness assumptions. Finally, performance evaluation is conducted from aspects such as computational costs, batch verification efficiency, tracking malicious users efficiency, and smart contract gas consumption. The results show that the proposed scheme can provide an efficient and reliable communication protocol for secure electronic voting systems.

Key words: conditional privacy preservation, certificateless ring signcryption, batch verification, smart contract

摘要： 将区块链技术应用在各种应用场景下已成为研究热点，区块链技术与电子投票系统的结合在保证投票人匿名性的同时还可以保障投票数据不被篡改，使投票结果更加公正可信。一方面可以解决传统投票方式带来的中心服务器可能丢失选票数据的问题。另一方面还可以保护投票者的数据隐私，提高投票的公平性与安全性。然而也存在着用户数量增多时验证选票效率较低的问题，以及存在恶意用户进行多次投票影响最终投票结果的问题。针对上述问题，提出了一种基于无证书密码体制的条件隐私保护环签密方案。该方案能够在保证降低计算开销的情况下提供安全的电子投票通信。通过将跟踪标记添加到签密消息中，设计了一种针对恶意用户的跟踪算法，使受信任方能够从环成员列表中识别出恶意投票用户。采用批量验证算法提高了验证效率，利用智能合约计票减少了对第三方机构的依赖。通过安全性分析，证明了该方案在椭圆曲线离散对数和椭圆曲线计算Diffie-Hellman困难性假设下基于随机谕言机模型是安全的。最后从计算开销、批量验证效率、追踪恶意用户效率和智能合约gas消耗等方面进行了性能评估，分析结果表明该方案可以为电子投票系统的安全相关应用提供高效、高可靠的通信协议。

关键词: 条件隐私保护, 无证书环签密, 批量验证, 智能合约