一个无证书强指定验证者签名方案的安全性分析与改进

Security Analysis and Improvement of Certificateless Strong Designated Verifier Signature Scheme

Hafizul Islam SK和G.P.Biswas最近基于椭圆曲线双线性对提出一个无证书强指定验证者签名方案,并声称该方案在三类敌手攻击模型下是可证明安全的,即第一类只得到系统公开参数和公钥的敌手,第二类可替换签名和验证者公钥的敌手,第三类可得到系统主密钥的敌手。分析该强指定验证者签名方案不能抵抗第三类敌手的攻击,亦即第三类敌手可以伪造有效的签名。针对此缺陷,对该无证书强指定验证者签名方案做了改进,在改进方案中,验证者的秘密私钥(由参与者独立产生的私钥)参与签名的验证计算,因此有效避免了原有方案的安全缺陷。最后对改进方案作了安全性分析,说明改进方案确实能抵抗三类敌手的攻击。

Hafizul Islam SK and G. P. Biswas recently proposed a certificateless strong designated verifier signature scheme based on elliptic curve bilinear pairing, and claimed their scheme satisfies provable security against three types of adversaries, including the type 1 adversary who only learns the system public parameters, the type 2 adversary who can＇t obtain the private key of the user and the system master key, but can replace the user＇s public key, and the type 3 ad- versary who has obtained the system master key. However, this paper pointed out their signature scheme is actually not secure as claimed by presenting an attack launched by an adversary who has learned the system master key. Further- more, to make up this flaw, we also provided an revised certificateless strong designated verifier signature scheme in which the verifier＇ s partial private key generated by himsdf is included in the computation of the verification procedure, thus above attack can be efficiently resisted.