Modified Group Signature in Online Auction System

Group signature scheme allows members of a group to sign messages on behalf of the group, such that the resulting signature does not reveal the identity of the signer. Signatures can be verified with respect to a single group public key. In case of dispute, only a designated group manager, because of their special property, is able to open signatures, and thus reveal the signer's identity. Its applications are widespread used, especially in e-commerce such as e-cash, e-voting and e-auction. On the other hand, internet is an open environment, and the unsecured environment can obstruct the development of e-commerce.