Abstract: The existed forward secure proxy signature schemes have some security faults more or less. This paper analyzes the security of a forward secure proxy signature scheme proposed by Chen Ningyu et al. The analysis result shows that the scheme cannot satisfy the forward security, cannot resist the collusion attack of PKG and the proxy signer, the attack of public key substituted and the forgery attack of the distrusted PKG. To get over the faults of Chen Ningyu’s scheme, an improved forward secure proxy signature scheme is proposed in this paper. The improved scheme satisfies all the security requirements of forward secure proxy signature scheme, moreover, it can resist the collusion attack, the distrusted PKG’s forgery attack and the public key substituted attack.

Key words: proxy signature, forward secure, certificateless signature, collusion attack, public key substituted

摘要： 已有的前向安全代理签名方案或多或少存在一些安全缺陷。针对陈宁宇等人的前向安全的代理签名方案进行安全性分析，发现该方案不满足前向安全性，无法抵抗PKG和代理签名人的合谋攻击，公钥替换攻击以及不诚实的PKG的伪造攻击。提出一个改进的前向安全代理签名方案，改进的方案满足前向安全的代理签名的所有安全性要求，同时能很好地抵抗合谋攻击、不诚实的PKG的伪造攻击和公钥替换攻击。

关键词: 代理签名, 前向安全, 无证书签名, 合谋攻击, 公钥替换