Avoiding loss of fairness owing to failures in fair data exchange systems

Fair exchange between mutually distrusted parties has been recognized as an important issue in electronic commerce. However, the correctness (fairness ) of the existing fair exchange protocols that use a Trusted Third Party (T TP) is based on the assumption that during an exchange there are no failure s at any of the local systems involved in the exchange, which is too strong in many situations. This paper points out that (1) system failures may cau se loss of fairness, and (2) most of the existing fair exchange protocols t hat use a TTP cannot ensure fairness in presence of system failures. This p aper presents two categories of techniques, transaction-based approaches an d message-logging-based approaches. to help develop data exchange systems t hat can recover from system failures without losing fairness. (C) 2001 Else vier Science B.V. All rights reserved.