Dynamic Fair Electronic Cash System without Trustees

A new fair electronic cash system is proposed based on group blind signature and secret sharing scheme. The proposed system is dynamic: we give the blind Bresson´s membership revocation method and apply it to deleting the dishonest banks that maybe attack the system. The proposed scheme does not need a trusted third party to trace users: a shop owning suspicious e- coin and the bank having issued the coin can collaborate to find the user using secret sharing scheme. A novel e-coin tracing method is used to prevent criminal activities and our scheme is constructed for multiple banks as in the real life, thus it is more practical.