## Cryptology ePrint Archive: Report 2007/456

Precise Zero-Knowledge in Concurrent Setting

Ning Ding and Dawu Gu

Abstract: We present a stronger notion of zero-knowledge: precise concurrent zero-knowledge. Our notion captures the idea that the view of any verifier in concurrent interaction can be reconstructed in the almost same time (within a constant/polynomial factor). Precise zero-knowledge in stand-alone setting was introduced by Micali and Pass in STOC'06 (The original work used the term "local zero-knowledge".). Their notion shows that the view of any verifier can be reconstructed in the almost same time in stand-alone setting. Hence our notion is the generalization of their notion in concurrent setting.

Furthermore, we propose a $\omega (\log ^2 n)$-round concurrent zero-knowledge argument for ${\rm{NP}}$ with linear precision, which shows that the view of any verifier in concurrent interaction can be reconstructed by the simulator with linear-time overhead. Our argument is Feige-Lapidot-Shamir type which consists of a proof-preamble and a proof-body for a modified NP statement. Our result assumes the restriction of adversarial scheduling the communication that the concurrent interaction of preambles of all sessions will be scheduled before any proof-body by the adversarial verifier.

Category / Keywords: foundations /

Date: received 7 Dec 2007, withdrawn 16 Mar 2008

Contact author: dingning at sjtu edu cn

Available format(s): (-- withdrawn --)

Short URL: ia.cr/2007/456

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