Anonymous Fair Exchange Protocol with a Semitrusted Third Party

Anonymity attracts wide attention in the electronic transaction, but participants usually do not trust each other. The problem inspires researchers to provide fair exchange protocol based on the third party. However, the third party is fully trusted and vulnerable to attack. This paper proposes an asynchronous optimistic fair exchange protocol. One of the important contributions is to preserve the anonymity even against a semitrusted third party. More importantly, the proposed protocol has minimal dependencies on the semitrusted third party as participants are forced to be honest. Meanwhile, the monopoly information owner can exchange the authentication information with different participants. Security analysis and performance comparison show that our constructions not only ensure transaction privacy and fairness, but also enjoy high efficiency.