[Resource Topic] 2020/649: NIZK from SNARG

Welcome to the resource topic for 2020/649

Title:
NIZK from SNARG

Authors: Fuyuki Kitagawa, Takahiro Matsuda, Takashi Yamakawa

Abstract:

We give a construction of a non-interactive zero-knowledge (NIZK) argument for all NP languages based on a succinct non-interactive argument (SNARG) for all NP languages and a one-way function. The succinctness requirement for the SNARG is rather mild: We only require that the proof size be |\pi|=\mathsf{poly}(\lambda)(|x|+|w|)^\delta for some constant \delta<1, where |x| is the statement length, |w| is the witness length, and \lambda is the security parameter. Especially, we do not require anything about the efficiency of the verification. Based on this result, we also give a generic conversion from a SNARK to a zero-knowledge SNARG assuming the existence of one-way functions where SNARK is a SNARG with the knowledge-extractability. For this conversion, we require the SNARK to be fully succinct, i.e., the proof size is \mathsf{poly}(\lambda)(|x|+|w|)^{o(1)}. Before this work, such a conversion was only known if we additionally assume the existence of a NIZK. Along the way of obtaining our result, we give a generic compiler to upgrade a NIZK for all NP languages with non-adaptive zero-knowledge to one with adaptive zero-knowledge. Though this can be shown by carefully combining known results, to the best of our knowledge, no explicit proof of this generic conversion has been presented.

ePrint: https://eprint.iacr.org/2020/649

Talk: https://www.youtube.com/watch?v=dv8LcMGFu7g

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