Robust multiparty computation with faster verification time

Abstract

In Eurocrypt 2016, Kiayias, Zhou and Zikas (KZZ) have designed a multiparty protocol for computing an arbitrary function, which they prove to be secure in the malicious model with identifiable abort supporting robustness property. In their algorithm, the total transaction verification time has turned out to be O(n6), where n is the number of parties participating in the protocol. The main contribution of this paper is the improvement of their verification time to O(n3 log n). We achieve this by observing that a deposit transaction created by a party in KZZ can be generated simply from the information contained in a different deposit transaction. This observation coupled with a host of novel techniques for addition and elimination of elements on a set relevant for our protocol is primarily the reason we were able to improve the verification time complexity of the KZZ protocol. Our trick can potentially be applied to speed up many other similar protocols (as much as it is prohibitive in some other specific scenarios). We compare our protocol with the others, based on various performance and security parameters, and, finally discuss the feasibility of implementing this in the Ethereum platform.