Group signatures: Better efficiency and new theoretical aspects

A group signature scheme allows members of a group to anonymously sign messages. To counter misuse, the anonymity can be revoked by the so-called group manager. This paper contributes two results to the area of group signatures. First, we improve the state-of-the-art scheme by Ateniese et al. by an order of magnitude. Our new scheme satisfies the recent security definition by Bellare et al. Second, and of a more theoretical nature, we study the Bellare et al. definitions and show that their notion of full-anonymity may require stronger assumptions than what is needed to achieve a relaxed but reasonable notion of anonymity. © Springer-Verlag Berlin Heidelberg 2005.