一种强不可伪造无证书签名方案的密码学分析与改进

无证书密码体制是无线网络中一种非常有效安全保护工具.2016年，Hung等人提出了标准模型下一种强不可伪造性的无证书签名方案，该方案声称在抗哈希碰撞问题和计算Diffle-Hellman困难问题假设下是安全不可伪造的.事实上，该方案对类型II敌手是不安全的.本文给出对Hung等的方案的安全性分析，并证明对于类型II敌手可以伪造出合法签名，针对存在问题提出一种改进的无证书签名方案.

Cryptanalysis and Improvement of a Certificateless Signature Scheme with Strong Unforgeability

Certificateless cryptographic schemes are very useful secure protection tools in wireless network.Quite recently,a certificateless signature with strong unforgeability in the standard model was presented by Hung et al.in 2016.Although they demonstrated that their scheme was secure and unforgeable under the collision resistant hash and computational Diffie Hellman assumptions,but we find that it is not secure against type II adversary.In this paper,we give security analysis to their scheme,and show that by giving concrete attack,a type II adversary could forge a legal signature of any message.We also put forward a possible fix of certificateless scheme which can solve secure problem.