Cryptology ePrint Archive: Report 2016/163

ZKBoo: Faster Zero-Knowledge for Boolean Circuits

Irene Giacomelli and Jesper Madsen and Claudio Orlandi

Abstract: In this paper we describe ZKBoo, a proposal for practically efficient zero-knowledge arguments especially tailored for Boolean circuits and report on a proof-of-concept implementation. As an highlight, we can generate (resp. verify) a non-interactive proof for the SHA-1 circuit in approximately 13ms (resp. 5ms), with a proof size of 444KB. Our techniques are based on the “MPC-in-the-head” approach to zero-knowledge of Ishai et al. (IKOS), which has been successfully used to achieve significant asymptotic improvements. Our contributions include: 1) A thorough analysis of the different variants of IKOS, which highlights their pro and cons for practically relevant soundness parameters; 2) A generalization and simplification of their approach, which leads to faster Sigma-protocols (that can be made non-interactive using the Fiat-Shamir heuristic) for statements of the form “I know x such that y = f(x)” (where f is a circuit and y a public value); 3) A case study, where we provide explicit protocols, implementations and benchmarking of zero-knowledge protocols for the SHA-1 and SHA-256 circuits;

Category / Keywords: implementation / zero knowledge

Original Publication (with minor differences): USENIX Security Symposium

Date: received 18 Feb 2016, last revised 12 Aug 2016

Contact author: giacomelli at cs au dk

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Version: 20160812:174525 (All versions of this report)

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