Concurrent Non-malleable Zero-knowledge Research Articles

Statistical Concurrent Non-Malleable Zero-Knowledge from One-Way Functions

Concurrent non-malleable zero-knowledge ($$\mathrm {CNMZK}$$) protocols are zero-knowledge protocols that provides security even when adversaries interact with multiple provers and verifiers simultaneously. It is known that $$\mathrm {CNMZK}$$ arguments for $$\mathcal {NP}$$ can be constructed in the plain model. Furthermore, it was recently shown that statistical$$\mathrm {CNMZK}$$ arguments for $$\mathcal {NP}$$ can also be constructed in the plain model. However, although the former requires only the existence of one-way functions, the latter requires the DDH assumption. In this paper, we construct a statistical $$\mathrm {CNMZK}$$ argument for $$\mathcal {NP}$$ assuming only the existence of one-way functions. The security is proven via black-box simulation, and the round complexity is $$\mathsf {poly}(n)$$. Under the existence of collision-resistant hash functions, the round complexity is reduced to $$\omega (\log n)$$, which is essentially optimal for black-box concurrent zero-knowledge protocols.

Concurrent non-malleable zero-knowledge and simultaneous resettable non-malleable zero-knowledge in constant rounds

Concurrent non-malleable zero-knowledge (CNMZK) considers the concurrent execution of zero-knowledge protocols in a setting even when adversaries can simultaneously corrupt multiple provers and verifiers. As far as we know, the round complexity of all the constructions of CNMZK arguments for NP is at least ω(logn). In this paper, we provide the first construction of a constant-round concurrent non-malleable zero-knowledge argument for every language in NP. Our protocol relies on the existence of families of collision-resistant hash functions, one-way permutations and indistinguishability obfuscators. As an additional contribution, we study the composition of two central notions in zero knowledge, the simultaneously resettable zero-knowledge and non-malleable zero-knowledge, which seemingly have stronger proved security guarantees. We give the first construction of a constant-round simultaneously-resettable non-malleable zero-knowledge. To the best of our knowledge, this is the first study to combine the two security concepts described above together in the zero-knowledge protocols.

A New Construction of Concurrent Non-malleable Zero-Knowledge

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.

Concurrent non-malleable statistically hiding commitment

We present a modular construction of non-malleable statistically hiding commitment schemes that retains its properties when concurrently executed a polynomial number of times. Our protocol is based on a statistically hiding commitment scheme and a concurrent non-malleable zero-knowledge protocol for all of NP. Our result is achieved in the plain model without relying on any set-up assumptions. The proof of security only uses black-box techniques.