Fair and Secure Multi-Party Computation with Cheater Detection

Abstract

Secure multi-party computation (SMC) is a cryptographic protocol that allows participants to compute the desired output without revealing their inputs. A variety of results related to increasing the efficiency of SMC protocol have been reported, and thus, SMC can be used in various applications. With the SMC protocol in smart grids, it becomes possible to obtain information for load balancing and various statistics, without revealing sensitive user information. To prevent malicious users from tampering with input values, SMC requires cheater detection. Several studies have been conducted on SMC with cheater detection, but none of these has been able to guarantee the fairness of the protocol. In such cases, only a malicious user can obtain a correct output prior to detection. This can be a critical problem if the result of the computation is real-time information of considerable economic value. In this paper, we propose a fair and secure multi-party computation protocol, which detects malicious parties participating in the protocol before computing the final output and prevents them from obtaining it. The security of our protocol is proven in the universal composability framework. Furthermore, we develop an enhanced version of the protocol that is more efficient when computing an average after detecting cheaters. We apply the proposed protocols to a smart grid as an application and analyze their efficiency in terms of computational cost.

Efficient Fair and Robust SPDZ-Like Multi-Party Computation

“…The decryption is not necessary if all parties behave honestly for opening the shares. Our scheme provides better privacy than [17] as the secret aggregation or decryption is performed by the computing parties, not the TTP. The inability of adversaries to know the output until successful delivery enables the player-elimination technique proposed in [11] to achieve fairness and robustness.…”

“…A robust MPC with identifiable abort is proposed in [16], where robustness is obtained by t-secure secret-sharing and needs ZKP for every share opening in the online phase. A cryptographic solution, described in [17], is suggested to achieve fairness, but it incurs high complexity and relies on an external party for decryption. Although our scheme also uses a TTP to provide encryption keys, it requires the ciphertexts of multiplicative ciphers in the offline phase, such that the online phase does not need to invoke cryptographic functionalities for the computation.…”