A Fair-Exchange Protocol Based on Off-line Semi-Trusted Third Party

The fairness of data exchange becomes a key factor for the transaction over the Internet. To ensure the fairness of data exchange, the protocol needs a trusted third party be a judge when the dispute occurs, and has to give a guarantee to main parties during the data exchange. To eliminate the third party's connectional time and enhance its security, a fair-exchange protocol based on off-line semi-trusted third party has presented in this paper. The protocol employs an off-line semi-trusted third party, where a flexible method for selecting a semi-trusted third party is proposed. Also, the proposed protocol is extended to Web services so that it can be used for main parties in different platforms.