Optimistic Fair Exchange in Cloud-Assisted Cyber-Physical Systems

Recently, optimistic fair exchange in electronic commerce (e-commerce) or mobile commerce (m-commerce) has made great progress. However, new technologies create large amounts of data and it is difficult to handle them. Fortunately, with the assistance of cloud computing and big data, optimistic fair exchange of digital items in cyber-physical systems (CPSes) can be efficiently managed. Optimistic fair exchange in cloud-assisted CPSes mainly focuses on online data exchange in e-commerce or online contracts signing. However, there exist new forms of risks in the uncertain network environment. To solve the above problems, we use a new technique called verifiably encrypted identity-based signature (VEIS) to construct optimistic fair exchange in cloud-assisted CPSes. VEIS is an encrypted signature, and we can check the validity of the underlying signature without decrypting it. We introduce a robust arbitration mechanism to guarantee fairness of the exchange, and even the trusted third party (TTP) cannot get the original signatures of the exchange parties. And the TTP in our protocol is offline, which greatly improves the efficiency. Besides, we show that our protocol is secure, fair, and practical.