Cryptology ePrint Archive: Report 2007/451

Precise Concurrent Zero Knowledge

Omkant Pandey and Rafael Pass and Amit Sahai and Wei-Lung Dustin Tseng and Muthuramakrishnan Venkitasubramaniam

Abstract: \emph{Precise zero knowledge} introduced by Micali and Pass (STOC'06) guarantees that the view of any verifier $V$ can be simulated in time closely related to the \emph{actual} (as opposed to worst-case) time spent by $V$ in the generated view. We provide the first constructions of precise concurrent zero-knowledge protocols. Our constructions have essentially optimal precision; consequently this improves also upon the previously tightest non-precise concurrent zero-knowledge protocols by Kilian and Petrank (STOC'01) and Prabhakaran, Rosen and Sahai (FOCS'02) whose simulators have a quadratic worst-case overhead. Additionally, we achieve a statistically-precise concurrent zero-knowledge property---which requires simulation of unbounded verifiers participating in an unbounded number of concurrent executions; as such we obtain the first (even non-precise) concurrent zero-knowledge protocols which handle verifiers participating in a super-polynomial number of concurrent executions.

Category / Keywords: foundations / Concurrent Zero Knowledge, Precise Simulation

Publication Info: Full version of a paper appearing at Eurocrypt 2008.

Date: received 4 Dec 2007, last revised 1 Feb 2008

Contact author: omkant at cs ucla edu

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Version: 20080201:100328 (All versions of this report)

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