Research And Analysis Of Group Signature

As a group-oriented special digital signature, group signature allows group members to sign a document on behalf of the group and provides signer's anonymity. In case of dispute, the group manager can reveal the ture identity of the signer. Owning to the main characters of group signature, it can be widely applied in the fields of electronic commerce and electronic government, such as electronic cash and electronic voting etc.To begin with, we analyze the security of Si Guangdong et al's group signature scheme and point that it is not satisfied with traceability and unforgeability. In fact, its open algorithm can not reveal the identity of signer. A method to forge is given. Secondly, we also point that the group signature scheme with low efficiency on dynamic update proposed by He Yefeng et al is not coalition-resistant through security analysis. The most fatal point is that the group member can sign even if he has been deleted before. Thirdly, we propose a new ID-based dynamic group signature scheme after analyzing amount of ID-based group signature schemes, which has an efficient dynamic update algorithm, with only once multiply operation. Thus, the sizes of signature and key are independent on the quantity of the group members. At the same time, the scheme can trace the group member who do the coalition attack according to the open algorithm. Finally, we try to apply the group signature above to the electronic cash system and propose a new off-line electronic cash scheme. Through making the best of the characteristics of ID-based group signature and bilinear map, a new format of electronic cash and a new method of verifying electronic cash's legitimacy are given too.