International Association for Cryptologic Research (IACR)
Abstract
A group signature scheme allows a
group member of a given group to sign messages on behalf of
the group in an anonymous and unlinkable fashion. In case of
a dispute, however, a designated group manager can reveal
the signer of a valid group signature. Many applications of
group signatures require that the group manager can be split
into a membership manager and a revocation manager. Such a
group signature scheme with strong separability was proposed
in paper [1]. Unfortunately, the scheme is insecure which has been shown in [2][3][4]. In this paper
we show that the scheme is untraceable by a simple and direct attack. Besides, we show its universal forgeability by a
general attack which only needs to choose five random numbers.
We minutely explain the technique to shun the challenge in
the scheme
