摘要：Mediated Signature Scheme provides an efficient method for fast revocation of a user’s identity in identity (ID)-based cryptosystems. The only ID-based mediated signature scheme was proposed by Cheng et al. from bilinear pairing in [8]. Unfortunately, their scheme has an inherent flaw that the PKG is fully capable to generate a valid mediated signature of some message on behalf of its signers by only utilizing the public information of the system. In this paper, an efficient ID-based mediated signature scheme without trusted PKG is proposed. Compared with the scheme [8], the proposed scheme has other property besides achieving immediate revocation of a signer’s ID. That is, proposed scheme is ID-based, but without any assumption of pre-fixed trusted relationship between users and PKG, which effectively solves the problem that exists in some existing ID-based public key cryptosystems in which a trusted PKG and key escrow are needed.
关键词：ID-based signature; ID-based mediated signature; without trusted PKG; immediate revocation; GDH group
