Abstract: This paper analyzes the security of a certificateless proxy signature scheme and shows that it is insecure against the public key replacement attack in certificateless cryptosystems. The attack method is presented, in which adversary can forge a signature of any message by substituting the public keys of the original signer and the proxy signer. An improved scheme is presented to defense against this public key replacement attack.

Key words: certificateless signature, proxy signature, public key replacement attack, hash function, bilinear pairings

摘要： 对无证书代理签名方案进行安全性分析，指出该方案对于公钥替换攻击是不安全的，并给出具体的攻击方法。在这种攻击下，对任意指定的原始签名者和代理签名者，敌手总可以通过替换原始签名者和代理签名者的公钥伪造任意消息的代理签名。为防御该种公钥替换攻击，提出利用单向性的散列函数将公钥与其他信息进行绑定的改进措施。

关键词: 无证书签名, 代理签名, 公钥替换攻击, 散列函数, 双线性对

CLC Number: 

• TP309