An Alternative Approach to Non-black-box Simulation in Fully Concurrent Setting, by Susumu Kiyoshima

We give a new proof of the existence of public-coin concurrent zero-knowledge arguments for NP in the plain model under the existence of collision-resistant hash function families, which was originally proven by Goyal (STOC'13). 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.