group signatures的用法和樣例：
例句
- Group signature schemes are extended from ordinary digital signatures motivated by a variety of applications.
摘要群簽名是對一般數字簽名的一種擴展，有很多重要應用。 - The cost of revoking a member and updating witness is smaller than the previous accumulators.The security of the new group signature scheme is proved.
撤銷一個成員和更新證據所花費的代價比以前的累加器更小，而且證明了新的群簽名的安全性。
