Efficient Fair Conditional Payments for Outsourcing Computations

Xiaofeng Chen, Jin Li, Willy Susilo

Abstract: 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 <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$T$</tex></formula> to achieve the fairness and efficiency. However, <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$T$</tex> </formula> 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.