An Extended Payment Model for M-Commerce with Fair Non-Repudiation Protocols

commerce, is still at the start. In this paper, we propose an extension of existing mobile payment models to introduce an extended mobile payment service (EMPS) model, which is based on assumptions about the cooperation between mobile network operators and financial institutions to deal with different payment amounts ranging from micro to macro payment. The novel model focuses on enhancement of non-repudiation problem. Fair non-repudiation protocols are developed for not only payment phase but also other phases in a typical m-commerce transaction, including price negotiation and content delivery. Joint signatures method is used in protocols to overcome the limitations in mobile handheld device capability and to reduce the trust dependence totally on the payment service. As with the proposed non-repudiation protocols, EMPS plays the role of a semi-trusted third party and is an indispensable factor for creating the fairness property. Non-repudiation analyses of these protocols are also conducted besides some guidelines for ensuring non-repudiation in m-commerce.