无双线性对的无证书(广义)签密方案安全性分析

Cryptanalysis of Certificateless(Generalized)Signcryption Schemes Without Bilinear Pairing

为避免双线性对运算较耗时的缺陷,提高(广义)签密方案效率,学界提出了无双线性对运算的无证书签密方案和无双线性对运算的无证书广义签密方案。在随机预言机模型下证明该方案满足机密性和不可伪造性。通过具体的攻击方法证明了前一个方案存在伪造性攻击而后一个方案存在机密性攻击,分析了原方案不安全的原因。通过将公钥进行hash运算对前一个方案进行了改进,通过把签名部分分成两部分对后一个方案也进行了改进。对改进方案效率进行分析,结果表明改进方案安全高效。

To avoid the time consuming bilinear pairing operations and improve the efficiency of(generalized)signcryption schemes, we proposed a certificateless signcryption scheme and a certificateless generalized signcryption scheme without bilinear pairing,re-spectively. The confidentiality and unforgeability of the schemes in the random oracle model were proved. By giving concrete attacks, the former scheme was proved to be vulnerable to forgery attack and the latter one to confidentiality attack. The reason why the original schemes were insecure was analyzed. An improved scheme was given to the former one by hashing the public key and an improved scheme was given to the latter one by dividing the signature part into two parts. At last,the efficiency of the improved schemes was ana-lyzed,which showed they were high efficient.