Efficient Fair Conditional Payments for Outsourcing Computations

The outsourcing computations in distributed environments suffer from the trust problems between the outsourcer and the workers. All existing solutions only assume the rational lazy-but-honest workers. In this paper, we first introduce the rational lazy-and-partially-dishonest workers in the outsourcing computation model. In addition, we propose a new fair conditional payment scheme for outsourcing computation that is only based on traditional electronic cash systems. The proposed construction uses a semitrusted third party T to achieve the fairness and efficiency. However, T is only involved in the protocol in the exceptional case, namely in the case of disputes. Moreover, since neither the secret sharing/splitting scheme nor the cut-and-choose protocol is used for the generation or verification of the payment token, our solution clearly outperforms the existing schemes in terms of efficiency.