Efficient and secure protocol in fair document exchange

This paper presents a new fair document exchange protocol based on bilinear pairing with off-line trusted third party (TTP). In such a fair exchange scenario, each party owns a valuable message. The protocol is executed with the help of verifiable encrypted message, which could be verified and decrypted by different parties, respectively. Once a party verifies that the exchangeable message could be decrypted by TTP, he firstly sends his own message in that TTP has already provided fairness. Furthermore, to pass verification, each message should be wrapped into a commit message and be certified by an authority. We give an efficient and secure construction by using bilinear pairing. Eventually, we analyze the secure issues and compare our protocol's efficiency with others.