Sender Fairness definition
Sender Fairness. If honest S does not obtain any information about i𝒳 other than desc𝒳, then R cannot obtain any information about iS other than descS . A relaxed notion of fairness is defined as probabilistic fairness where the chance of violating fairness is restricted with an arbitrarily low probability [21], [22], [23]. It has been shown that fairness cannot be achieved without a trusted third party [1]. In a minimal setting of using TTP, named as optimistic fair exchange [24], a TTP needs to be involved to solve the disputes between parties. Here, parties prove their claims to TTP by comparing the obtained output and the initially agreed description. Recent proposals use a blockchain as a TTP since it is practical and cost friendly. Now, we first present the exchange protocols assuming the description is known in advance. Later, we explain the protocols where the description is not available, which is also the scenario assumed in this work.