An E-Cash Payment Protocol Realizing Accountability and Fairness

The paper proposes an improvement of e-cash payment protocol. One improvement is to divide the "agreement" and "use" of the session key into two stages, which ensures its key confidentiality. The second improvement is that the identities of the merchants are proved by their electronic certificates, which realizes its non-repudiation. The third improvement is that the payment receipts are transmitted by the trusted party, which avoids unfairness arisen by the dishonest entities. In addition, the protocol uses FTP to transmit e-cashes and payment receipts, which can ensure achievement of accountability and fairness, and enhance the robustness. The proposed protocol is verified to satisfy accountability and fairness by utilizing the improved Kailar logic.