Abstract: This paper analyzes the security of a new certificateless proxy signature proposed by Fan Rui recently.The security of Fan Rui’s scheme relies on the CDH problem.It shows that Fan’s proxy signature reveals the private key of original signer and is insecure against a key replacement attack and malicious-but-passive KGC attack.It also gives a modified scheme.The improvement is secure against the key replacement attack and the malicious-but-passive KGC attack.This paper elaborately eliminates the defect of the original scheme and improves the efficiency of the protocol.

摘要： 樊睿等人提出了一种新的无证书代理签名方案，该方案的安全性是基于CDH困难性假设。对该代理签名方案进行了安全性分析，指出该方案不仅泄露了原始签名者的私钥，而且不能抵抗替换公钥攻击和恶意但被动的KGC攻击，从而不满足代理签名的安全性要求。同时提出了一个改进方案，改进方案不仅弥补了原方案的安全缺陷，而且改善了协议的性能。