关键词: 代理签名, 无证书签名, 合谋攻击, 双线性对

Abstract: This paper analyzes the security of the certificateless proxy signature scheme that Liu Xiaohong and Zhang Jianzhong proposed. The analysis shows that Liu and Zhang’s scheme cannot resist the attack of malicious KGC and the collusion attack among the original signer, the proxy signer and KGC. To get over these security problems, an improved scheme is proposed. The security analysis shows that the improved scheme can overcome the above mentioned problems.

Key words: proxy signature, certificateless signature, collusion attack, bilinear pairing