Paper 2015/067

Non-black-box Simulation in the Fully Concurrent Setting, Revisited

Susumu Kiyoshima

Abstract

We give a new proof of the existence of $O(n^{ϵ})$-round public-coin concurrent zero-knowledge arguments for NP, where $ϵ>0$ is an arbitrary constant. The security is proven in the plain model under the assumption that collision-resistant hash functions exist. (The existence of such concurrent zero-knowledge arguments was previously proven by Goyal (STOC'13) in the plain model under the same assumption.) In the proof, we use a new variant of the non-black-box simulation technique of Barak (FOCS'01). An important property of our simulation technique is that the simulator runs in a "straight-line" manner in the fully concurrent setting. Compared with the simulation technique of Goyal, which also has such a property, the analysis of our simulation technique is (arguably) simpler.

Note: This article is based on an earlier article: An Alternative Approach to Non-black-box Simulation in Fully Concurrent Setting, in Proceedings of TCC 2015, DOI: 10.1007/978-3-662-46494-6_13. The main result remains the same as before.