不含双线性对的无证书签密方案安全性分析与改进

Security Analysis and Improvement of Strongly Secure Certificateless Key Agreement Protocol

无证书密码体制能同时解决传统公钥密码体制证书管理问题和基于身份密码体制中密钥分发的问题,而受到学者们的关注。基于双线性对的无证书签密,因需要大量开销用于双线性对运算而性能不佳。研究不基于双线性对的无证书签密方案,发现Selvi等人的不基于双线性对的无证书签密方案不是标准的无证书签密方案,因为用户在使用时必须先验证对方的公钥,这不仅与无证书公钥体制相背,而且增加了用户的开销。分析了其他3个不基于双线性对的无证书签密方案,发现这3个方案都不满足不可伪造性和机密性。为解决这些安全性问题,提出一个新的不基于双线性对的无证书签密方案,并在随机预言机模型下证明了其安全性。

The certificateless public key cryptography （CLPKC） has attracted wide attention since it could solve the certificate management problem in the traditional public cryptography and the key escrow problem in the ID-based cryptography. Many certificateless signcryption （CLSC） schemes using pairing have been proposed. The pairing operation is a very complicated operation. So the performance of these schemes is not very good. In this paper, we study the CLSC schemes without pairing , and find that Selvi et al. Is scheme is not a standard CLSC scheme since the user must verify the public key before using it. This not only inverses the thought of the CLPKS but also increases the user＇s computational cost. To solve the problem, three new CLSC schemes without pairing have been proposed. In this paper, we will show the three CLSC schemes provide neither unforgeability property nor confidentiality property. To improve security, we also propose a new CLSC scheme without pairing and demonstrate it is provably secure in the random oracle model.