## Cryptology ePrint Archive: Report 2016/213

3-Message Zero Knowledge Against Human Ignorance

Nir Bitansky and Zvika Brakerski and Yael Kalai and Omer Paneth and Vinod Vaikuntanathan

Abstract: The notion of Zero Knowledge has driven the field of cryptography since its conception over thirty years ago. It is well established that two-message zero-knowledge protocols for NP do not exist, and that four-message zero-knowledge arguments exist under the minimal assumption of one-way functions. Resolving the precise round complexity of zero-knowledge has been an outstanding open problem for far too long.

In this work, we present a three-message zero-knowledge argument system with soundness against uniform polynomial-time cheating provers. The main component in our construction is the recent delegation protocol for RAM computations (Kalai and Paneth, TCC 2016B and Brakerski, Holmgren and Kalai, ePrint 2016). Concretely, we rely on a three-message variant of their protocol based on a {\em key-less} collision-resistant hash functions secure against uniform adversaries as well as other standard primitives.

More generally, beyond uniform provers, our protocol provides a natural and meaningful security guarantee against real-world adversaries, which we formalize following Rogaway's human-ignorance" approach (VIETCRYPT 2006): in a nutshell, we give an explicit uniform reduction from any adversary breaking the soundness of our protocol to finding collisions in the underlying hash function.

Category / Keywords: foundations /

Date: received 26 Feb 2016, last revised 18 Sep 2016

Contact author: omerpa at gmail com

Available format(s): PDF | BibTeX Citation

Short URL: ia.cr/2016/213

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