摘要:信息通过公共链路进行传输时极易遭受窃听、篡改等形式的网络攻击，因此有必要保障信息在传输过程中的机密性和完整性，而签密技术能够有效地实现上述目的.基于椭圆曲线，提出一种多接收者多消息签密方案，能够有效地适配到广播系统中.采用多密钥分发中心管理系统主密钥信息，且能够周期地更新各自的秘密信息，以抵抗对应的APT攻击.不同更新周期注册的用户相互之间能够通信，不会影响系统的可用性.提出了一种基于区块链的周期更新策略，根据公有链中区块高度和时间戳触发密钥更新动作，基于区块链不可篡改特性确保方案的安全性，且该过程不需要执行交易动作，因此是免费的.基于Computational Diffie-Hellman问题和离散对数问题，在随机预言机模型下证明了签密方案的机密性和不可伪造性，该方案同时具有密钥托管安全性、前后向兼容性、不可否认性.性能分析表明，该签密方案具有较短的密文长度和较高的执行效率.在实验仿真部分，首先分析了密钥分发中心数量和门限值对签密算法性能的影响，在排除网络延迟等因素干扰下，引入多密钥分发中心后，性能损耗在5%以内；其次，基于区块链实现周期更新时的时间误差百分比会随周期的增加而下降，当周期大于550s时，其值控制在1%以内.这种误差使得攻击者很难预测更新的准确时间，增大了攻击的难度.



Abstract:When data is transmitted through the network, it is vulnerable to network attacks such as eavesdropping and tampering. Therefore, data confidentiality and data integrity should be guaranteed which can be achieved with the signcryption schemes. Based on the elliptic curve, a multi-receiver multi-message signcryption scheme is proposed, which can be effectively adapted to many scenarios such as broadcast systems. Multiple key distribution centers are used to manage the system master key, and the secrets of each center can be updated periodically to resist the APT attacks. In addition, users registered in different periods can communicate with each other to improve the availability. A secret update strategy based on the public blockchain is proposed, and the update operation is triggered based on the block height and the block timestamp. Blockchain, with its non-tampering feature, can guarantee security of the proposed scheme. In addition, the new scheme does not need to send transactions and is therefore free. Based on the computational Diffie-Hellman problem and the discrete logarithm problem, confidentiality and unforgeability of the proposed scheme are analyzed on the random oracle model. The proposed scheme also has the following security attributes:key escrow security, forward and backward compatibility, and non-repudiation. Performance analysis shows that the proposed scheme has a shorter ciphertext length and higher efficiency. In the simulation part, influence of the number of key distribution centers and the threshold on the system performance is analyzed. Without considering the network delay and other disturbing factors, the performance loss is less than 5% for the proposed scheme compared with those with a single key distribution center. The time errors incurred by the update strategy based on blockchain decrease with the increasing periods. When the period is set more than 550s, the time error percentage is less than 1%. The time errors make it more difficult for the attackers to predict the update time and launch the attacks.



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