Abstract Fairness is a security notion of secure computation and cannot always be achieved if an adversary corrupts a majority of parties in standard settings. Lindell (CT-RSA 2008) showed that imposing a monetary penalty on an adversary can circumvent the impossibility. He formalized such a security notion as “legally enforceable fairness" for the two-party setting based on the ideal trusted bank functionality and showed a protocol achieving the requirements. Based on the same framework, we introduce secure multi-party computation with legally enforceable fairness that is applicable for an arbitrary number of parties. Further, we propose two protocols that realize our introduced functionality. The first one achieves O(n) rounds and $O(n \alpha )$ O ( n α ) fees, where n is the number of parties, and $\alpha$ α is a parameter for the penalty amount. The fee refers to the balance amount in the bank required at the beginning of the protocol, which evaluates the difficulty of participating in the protocol in a financial sense. The second one achieves O(1) rounds and $O(n^2 \alpha )$ O ( n 2 α ) fees.Abstract Fairness is a security notion of secure computation and cannot always be achieved if an adversary corrupts a majority of parties in standard settings. Lindell (CT-RSA 2008) showed that imposing a monetary penalty on an adversary can circumvent the impossibility. He formalized such a security notion as “legally enforceable fairness" for the two-party setting based on the ideal trusted bank functionality and showed a protocol achieving the requirements. Based on the same framework, we introduce secure multi-party computation with legally enforceable fairness that is applicable for an arbitrary number of parties. Further, we propose two protocols that realize our introduced functionality. The first one achieves O(n) rounds and $$O(n \alpha )$$ O ( n α ) fees, where n is the number of parties, and $$\alpha $$ α is a parameter for the penalty amount. The fee refers to the balance amount in the bank required at the beginning of the protocol, which evaluates the difficulty of participating in the protocol in a financial sense. The second one achieves O(1) rounds and $$O(n^2 \alpha )$$ O ( n 2 α ) fees.

International Journal of Information SecurityAug 29, 20244 citations

Legally Enforceable Fairness in Secure Two-Party Communication.

Yehuda Lindell

In the setting of secure multiparty computation, a set of mutually distrustful parties wish to securely compute some joint function of their private inputs. The computation should be carried out in a secure way, meaning that the properties privacy, correctness, independence of inputs, fairness and guaranteed output delivery should all be preserved. Unfortunately, in the case of no honest majority – and specifically in the important two-party case – it is impossible to achieve fairness and guaranteed output delivery. In this paper, we show how a legal infrastructure that respects digital signatures can be used to enforce fairness in two-party computation. Our protocol has the property that if one party obtains output while the other does not (meaning that fairness is breached), then the party not obtaining output has a digitally signed cheque from the other party. Thus, fairness can be “enforced ” in the sense that any breach results in a loss of money by the adversarial party. 1In the setting of secure multiparty computation, a set of mutually distrustful parties wish to securely compute some joint function of their private inputs. The computation should be carried out in a secure way, meaning that the properties privacy, correctness, independence of inputs, fairness and guaranteed output delivery should all be preserved. Unfortunately, in the case of no honest majority – and specifically in the important two-party case – it is impossible to achieve fairness and guaranteed output delivery. In this paper, we show how a legal infrastructure that respects digital signatures can be used to enforce fairness in two-party computation. Our protocol has the property that if one party obtains output while the other does not (meaning that fairness is breached), then the party not obtaining output has a digitally signed cheque from the other party. Thus, fairness can be “enforced ” in the sense that any breach results in a loss of money by the adversarial party. 1

Chicago Journal of Theoretical Computer ScienceJan 1, 20092 citations

Secure Multi-Party Computation without Agreement

Shafi Goldwasser, Yehuda Lindell

Journal of CryptologyMay 20, 2005112 citations

Secure multi-party computation

Yan Huang

Elsevier eBooksJan 1, 202036 citations

O(n \alpha )

O ( n α ) fees, where n is the number of parties, and

\alpha

α is a parameter for the penalty amount. The fee refers to the balance amount in the bank required at the beginning of the protocol, which evaluates the difficulty of participating in the protocol in a financial sense. The second one achieves O(1) rounds and

O(n^2 \alpha )

O ( n 2 α ) fees.