Efficient and Generalized Group Signatures

The concept of group signatures was introduced by Chaum et al. at Eurocrypt ’91. It allows a member of a group to sign messages anonymously on behalf of the group. In case of a later dispute a designated group manager can revoke the anonymity and identify the originator of a signature. In this paper we propose a new efficient group signature scheme. Furthermore we present a model and the first realization of generalized group signatures. Such a scheme allows to define coalitions of group members that are able to sign on the group’s behalf.