An Efficient Fair Payment System by Electronic Wallet

Electronic payment systems are well-understood to be an essential step on the road to electronic commerce, and are thus in high demand. There has been a strong effort in developing secure untraceable off-line electronic cash protocols since Chaum proposed the first e-cash system in 1991 and some systems are now in use. However, there are still many open problems in the field of e-payment system research. The basic problems with all electronic payment systems for issuers of e-cash are to prevent double spending and to prevent kidnap and laundering. For the using of credit card in transaction is very popular, it is proper to design e-payment system based on smart card. There are many researchers making great efforts to do this work and gain some useful results. In this paper, an efficient fair payment system by electronic wallet is presented. Users in the system have only one personal account in the bank. In the withdrawal protocol, the user gives a correctly constructed message for possibly coin tracing to the bank and gets a blind signature on his identity from the bank. In the payment protocol, with the help of tamper-resistance card, the user proves to the shop that he spends a valid e-cash and sends a correctly constructed message for possibly owner tracing to the shop. A valid e-cash can be deposited to the bank by the shop. If a user spends an e-cash more than one times, with the help of the Trustee, the bank can find the user easily. Unlike other systems, the Trustee in this system is off-line entirely, it does not need to be involved in any protocols except the owner-tracing and coin-tracing protocols. The security of the system is based on the discrete logarithm problem. Upon the analyses, it indicates that the system is secure and efficient.