Anonymous fair transaction protocols based on electronic cash

It is important for electronic transactions to be fair because customers and merchants cannot interact face-to-face. Several proposed fair transaction protocols deal adequately with the fairness issue but not with the equally critical matters of customer anonymity and privacy. This paper proposes a novel fair transaction protocol based on electronic cash that achieves both anonymity and fairness. Utilizing an off-line trusted third party (TTP), the protocol is efficient and practical. The customer's anonymity and privacy are protected because payment information is not revealed to anyone, including the TTP. The proposed method is independent of the underlying electronic cash scheme and thus can be realized with any e-cash system based on blind signatures. It also offers anonymity revocation to prevent crime and solves the unlimited-growth problem of the bank's e-cash database.