An Abuse-Free Optimistic Fair Exchange Protocol Based on BLS Signature

The fair exchange protocol is one of the most fundamental cryptographic tool in many security applications such as contract signing protocols, certified e-mail systems, and e-payment schemes. BLS short signature (due to Boneh, Lynn, and Shacham) is among the most popular cryptographic primitives in pairing-based cryptography. We propose a new fair exchange protocol which can be used to exchange BLS signatures. To the best of our knowledge, it is the first abuse-free optimistic fair exchange protocol based on the BLS signature. And we show that it is both secure and efficient.