Abstract: Two properties of electronic contract protocol are pointed out, which are the both sides' equal position and the freedom of valid electronic contract evidence. Based on the two properties, a new practical electronic contract protocol is proposed, which fairness is systematically analyzed. Thenew protocol needs the trusted third party only if the communication channel isdamaged or someone is not honest. When both sides play honestly, one side onlyneeds to unload two messages to successfully finish the protocol.

Key words: electronic contract, fair exchange, digital signature