Abstract: Through the security analysis of a forward secure proxy blind signature scheme proposed by Xiao Hongguang et al., it is pointed out that the scheme doesn’t resist the original signer’s forgery attack, which means a dishonest original signer is able to forge the proxy signing key. Meanwhile, the scheme doesn’t satisfy the untraceability and forward security. To solve the above problems, an improved scheme is presented. By improving the method of the delegate authorization and the process of blind signature, the improved scheme overcomes the security problems existing in the former scheme. Then based on discrete logarithm problem and quadratic residue problem, the security properties of unforgeability, strong blindness and forward security are analyzed. The analysis results show that the improved scheme satisfies the security requirements of a forward secure proxy blind signature scheme.

Key words: unforgeability, untraceability, forward security, proxy blind signature, quadratic residue problem

摘要： 通过对肖红光等人提出的一种前向安全的代理盲签名方案进行安全性分析，指出该方案不能够抵抗原始签名人的伪造攻击，不诚实的原始签名人可以伪造代理签名密钥。同时，该方案也不具有不可追踪性和前向安全性。针对上述问题，提出一个改进的方案。通过对代理授权方式和盲签名过程的改进，使得改进后的方案克服了原方案存在的安全性问题，并基于离散对数困难问题以及二次剩余困难问题，对方案的不可伪造性、强盲性、前向安全性进行了分析。分析结果表明，改进后的方案满足前向安全代理盲签名方案的安全要求。

关键词: 不可伪造性, 不可追踪性, 前向安全, 代理盲签名, 二次剩余困难问题