In fair exchange protocols, a protocol without trusted third party (TTP) cannot support fairness fully, and an off-line TTP protocol also needs TTP and suffers low efficiency when the agents of the protocol are malicious. Moreover, most of the current fair exchange protocols aim at exchanging specific items and thus lose their universality. With the method of lowload on-line TTP to tackle the above deficiency, a generic fair exchange protocol based on malicious agents was proposed, and properties affecting the fairness were analyzed. The analysis result shows that the protocol requires less on environments, provides universality on fair exchange, avoids most fairness problems in the current protocols, and keeps high efficiency.
