Camenisch群签名方案的改进和成员废除

如何缩短群签名的长度以及如何安全有效废除群成员是阻碍群签名走向实用的两个主要问题．该文对Camenisch群签名方案进行改进，通过缩短其所用知识签名的长度，达到缩短签名长度的目的，所提出的改进方案使签名由原来的2n 4元组缩短为n 5元组，长度缩短了近一半．同时利用公钥状态列表和可信时戳提出一个前向安全的高效群成员废除方案，这个方案的提出纠正了不能用证书撤销列表废除群成员的观点．该文还考虑了后加入成员的超前签名问题，所提出的成员废除方案能防止超前签名．

Improvement and Member Deletion of Camenisch's Group Signature Scheme

How to shorten the length of group signature and how to delete group members are two most important issues that stand in the way of real-world applications of group signatures.In this paper, an improvement of Camenisch's group signature scheme is made by improving the 1-out-of-n signature of knowledge used in the group signature.The improvement shortens the length of signature of knowledge to shorten the length of group signature.As a result, the signatures in the improved scheme is an (n+5)-tuple, contrasted against a (2n+4)-tuple of the original, and accordingly the lengths of the signatures of the improvement is about a half that of the original.Furthermore, a forward-secure member deletion scheme, using the Public-Key State List and the Trusted Timestamp, is proposed, thus the improper view that Certificate Revocation List (CRL) approach is unsuitable for group signatures is corrected.The proposed member deletion scheme is efficient, since it increases neither the computational complexity nor the length of the signatures of the original scheme.