Group signatures: Better efficiency and new theoretical aspects

A group signature scheme allows members of a group to sign messages anonymously. To counter misuse, the so-called group manager can revoke the anonymity. This paper contributes two results to the area of group signatures. First, we improve the state-of-theart 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.