Cryptology ePrint Archive: Report 1999/009

On the Existence of 3-Round Zero-Knowledge Protocols

Satoshi Hada and Toshiaki Tanaka

Abstract: In this paper, we construct a 3-round zero-knowledge protocol for any NP language. Our protocol achieves weaker notions of zero-knowledge than black-box simulation zero-knowledge. Therefore, our result does not contradict the triviality result of Goldreich and Krawczyk which shows that 3-round black-box simulation zero-knowledge exist only for BPP languages. Our main contribution is to provide a non-black-box simulation technique. Whether there exists such a simulation technique was a major open problem in the theory of zero-knowledge. Our simulation technique is based on a non-standard computational assumption related to the Diffie-Hellman problem, which was originally proposed by Damgard.

Category / Keywords: Zero-knowledge, interactive proofs, interactive arguments, Diffie-Hellman problem, NP.

Publication Info: Appeared in the THEORY OF CRYPTOGRAPHY LIBRARY and has been included in the ePrint Archive.

Date: received March 31, 1999. An earlier version has appeared in CRYPTO'98.

Contact author: hada at lab kdd co jp

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