Abstract: This paper points out that Li et al.’s two verifiable ring signature schemes do not satisfy the security property of unforgeability, i.e., any member in the ring can impersonate other members to generate the valid signature, and the real identity verification algorithm shows that the real identity of the signature is the latter. In order to remedy the aforementioned security defects of the two verifiable ring signatures chemes, this paper puts forward two improved schemes. The improved schemes combine the real identity verification algorithm with the signer’s private key, public key and the signature such that the attacker cannot forge valid signature of other signer without knowing the private key of the signer, and enhancing the security property of the original schemes.

Key words: verifiable ring signature, verifiable proxy ring signature, unforgeability, bilinear pairings

摘要： 指出李晓琳等人的两个可验证环签名方案提出分析都不满足不可伪造性，即环中成员可以冒充其他成员生成有效的环签名，而真实签名者身份验证算法却将签名者的身份指向后者。针对上述两方案存在的安全缺陷，分别提出了改进方案，通过将真实签名者身份验证算法与签名者的私钥、公钥及消息的签名有机地结合起来使得攻击者在不知道签名者私钥的情况下无法伪造其他签名者的有效签名，从而提高了原方案的安全性。

关键词: 可验证环签名, 可验证代理环签名, 不可伪造性, 双线性对