ID-Based Threshold Signature and Mediated Signature Schemes

One inherent drawback of current Identity based (ID- based) cryptosystems is that they cannot provide an efficient solution to immediately revoke a user´s identity. In this paper, we firstly propose an ID-based threshold signature scheme and show that it has the properties of unforge-ability and robustness. Then, inspired by Boneh et al.´s idea of mediated RSA, based on the proposed threshold signature scheme, we construct an ID-based mediated signature scheme, where an immediate revocation of a user´s identity in ID-based cryptosystems can be obtained.