Cryptology ePrint Archive: Report 2018/167

On the Existence of Three Round Zero-Knowledge Proofs

Nils Fleischhacker and Vipul Goyal and Abhishek Jain

Abstract: We study the round complexity of zero-knowledge (ZK) proof systems. While five round ZK proofs for NP are known from standard assumptions [Goldreich-Kahan, J. Cryptology'96], Katz [TCC'08] proved that four rounds are insufficient for this task w.r.t. black-box simulation.

In this work, we study the feasibility of ZK proofs using non-black-box simulation. Our main result is that three round private-coin ZK proofs for NP do not exist (even w.r.t. non-black-box simulation), under certain assumptions on program obfuscation. Our approach builds upon the recent work of Kalai et al. [Crypto'17] who ruled out constant round public-coin ZK proofs under the same assumptions as ours.

Category / Keywords: zero-knowledge, round complexity, lower bound

Original Publication (in the same form): IACR-EUROCRYPT-2018

Date: received 8 Feb 2018

Contact author: mail at nilsfleischhacker de, abhishek@cs jhu edu, goyal@cs cmu edu

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Version: 20180211:144457 (All versions of this report)

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