In 1999, Bao et al. proposed [6] a multi-party fair exchange protocol of electronic items with an offline trusted third party. In this protocol, a coalition including the initiator of the exchange can succeed in excluding a group of parties without the consent of the remaining entities. We show that every participant must trust the initiator of the protocol for not becoming a passive conspirator. We propose a new protocol in which the participants only need to trust the trusted third party. Moreover, under certain circumstances, if there are participants excluded from the exchange, they can prove that a problem occurred to an external adjudicator.
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