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The optimistic approach of involving a third party only in the case of exceptions is a useful technique to build secure, yet practical fair exchange protocols. Previous solutions using this approach implicitly assumed that players had reliable communication channels to the third party. We present a set of optimistic fair exchange protocols which tolerate temporary failures in the communication channels to the third party. A central feature of the protocols is that either player can asynchronously and unilaterally bring a protocol run to completion.
Asokan et al. (Wed,) studied this question.