Study And Design On Fair Electronic Payment Schemes

This thesis mainly discusses the fairness of E-cash and of E-payment protocols.Due to the inborn nature of easy duplication and reuse of E-cash, it is a requisite that the anonymity of E-cash be removed on certain occasions when necessary. To prevent the reuse of E-cash, we propose a new secure off-line E-cash scheme in this thesis. The symmetric cryptosystem is introduced to embed the identity information of the customer into E-cash, which guarantees the anonymity of a legal user. On the other hand, the identity of the user, be it the customer or merchant, who reuses the same piece of E-cash can be detected with efficiency at a considerable probability.In the second half of this thesis, we first introduce several categories of E-business protocols including secure electronic transaction protocols, electronic check protocols and fair electronic transaction protocols, all of which employ a trusted third party(TTP). The potential problems of their application in a no-trust environment are also presented. Then, a concurrent signature protocol, which realizes the fair exchange of signatures and which requires no TTP, is expounded. Finally, two fair E-Commerce protocols based on concurrent signatures are presented. One protocol aims at the transactions of electronic goods and the other is designed for the delivery of substantial goods. Neither of them needs any TTP. Finally, security analyses are given on both protocols respectively, showing that both the protocols satisfy fairness and security.