两种门限签名方案的密码学分析及其改进

Jan等和Gan分别提出了抗合谋攻击的门限签名方案。给出了一种合谋攻击方案表明他们的方案是不安全的,任何一组成员可以合谋假冒另一组成员对任何消息生成有效的门限签名而不需负任何责任。一旦事后发生纠纷,指定的秘书可以打开签名,而被假冒的成员无法否认签名。为克服他们的方案的安全性缺陷,给出了一个改进方案。并且,基于改进的方案,提出了一个可以追查签名者身份的、抗合谋攻击的门限签名方案。

Cryptanalysis and improvement of two threshold signature schemes

New threshold signature schemes withstanding the conspiracy attack were proposed by Jan and Gan, respectively. However, it would show that their schemes are insecure by presenting a conspiracy attack. Any set of the group could impersonate another set of members to sign any message without holding the responsibility. In case of disputes later, the designated clerk could open the forgery threshold signature, and all the members who were impersonated have no way to deny the signature. To overcome the weakness, a modification to the proposed schemes could satisfy the security requirement. Further, a variant with traceable signers based on the modified scheme is proposed.