A New Construction of Concurrent Non-malleable Zero-Knowledge

Abstract

This paper focuses on the robustness of concurrent non-malleable zero-knowledge.Existing concurrent non-malleable zero-knowledge protocols either apply non-black-box simulation techniques,or employ black-box simulation but incorporate a zero-knowledge sub-protocol.Hence when concurrently composed with other protocols,security of these protocols is not preserved or hard to argue.Following the well-known Feige-Shamir style,this paper presents a new construction for concurrent non-malleable zero-knowledge argument system,which is easily composed.This protocol takes the robust non-malleable commitment scheme introduced by Lin and Pass in STOC 2009 and specially designed witness indistinguishable proofs as basic components to achieve non-malleability and robustness.Moreover,this paper applies the "oblivious simulation" strategy to simulate the view of the adversary,and the proof technique introduced by Lin et al.in Crypto 2010 to analyze the indistinguishability of simulation.Since witness indistinguishability is closed under concurrent composition,the commitment sub-protocol is robust and the simulation is oblivious,when concurrently composed with other protocols,this protocol is easier to work with and analyze.Based on the one-way function assumption,the round complexity of this protocol is super-logarithmic.