基于身份部分盲签名方案的分析与改进

部分盲签名致力于解决匿名性和可控性之间的矛盾，在保护用户隐私的同时又能在必要时追溯用户身份。目前基于身份的部分盲签名方案中普遍存在公共信息被篡改的问题。通过对刘二根的方案的安全性分析，指出其方案中用户可以非法修改公共信息。在此基础上，提出一个改进的基于身份的部分盲签名方案。在随机预言模型下，基于离散对数困难问题，证明了方案在满足部分盲性的同时，能有效抵抗适应性选择消息下的存在性伪造攻击。新方案没有使用计算开销较大的双线性对运算，且克服了公共信息被篡改的缺陷，与现有方案相比，在安全和效率方面都有显著提高。

Analysis and improvement of an ID-based partially blind signature scheme

Partially blind signature is designed to adress the contradiction between anonymity and controllability, and it can protect the privacy of users and trace user identity when it is necessary. The problem is that the public information can be tampered by malicious parties, which exists in partially blind signature schemes based on identity. Security analysis of the Liu scheme shows that the user can modify public information illegally. On this basis, we propose an improved ID based partially blind signature. Based on the discrete logarithm problem, this scheme can satisfy the requirement of partial blindness while being capable of resisting against existential unforgeability attack of the adaptive chosen message under the random oracle model. The new scheme does not use the bilinear pairing operation with higher computational cost, and avoids public information tampering. Compared with existing schemes, it improves security and efficiency significantly.