Due to the growing interest in electronic commerce, more and more transactions now happen online. Thus, fair transactions between customers and merchants are getting important. To gain the fairness of the exchange of digital items, fair exchange protocols have been proposed and well studied. Most of the traditional fair exchange protocols are concerned about the exchange of digital items, such as digital signatures, contracts, and documents. Recently, researchers pay attention to the exchange of digital goods along with electronic cash, and have proposed some fair transaction protocols based on electronic cash. To buy digital contents via electronic cash through network, the anonymity property as traditional cash possesses must be guaranteed. It means that the payment information of the customer cannot be revealed to anyone else including the trusted third party (TTP) who helps the customer and the merchant with resolving possible disputes in the protocol. Since the customer and the merchant may not trust each other in an electronic transaction. In a fair exchange protocol, a TTP is employed to achieve true fairness. An on-line TTP has to take part in all transactions while they are proceeding. Despite it can gain true fairness, it is inefficient due to on-line interaction with the TTP. On the other hand, an off-line TTP does not need to join in the transaction protocol in normal cases. Instead, it participates in the protocol only when disputes happen. It is efficient and fair, and more feasible in practical situations. In this thesis, we propose a fair transaction protocol based on electronic cash. With the extended research on electronic cash, we have designed a fair transaction protocol that is suitable for any electronic cash system. By using an off-line TTP, the protocol is more efficient and practical. Furthermore, payment information of the customer cannot be known to anyone else including the TTP, and thus, the anonymity of the customer is protected completely in our protocol.