Cryptology ePrint Archive: Report 2001/051

Black-Box Concurrent Zero-Knowledge Requires $\tilde\Omega(\log n)$ Rounds

Ran Canetti, Joe Kilian, Erez Petrank, Alon Rosen

Abstract: We show that any concurrent zero-knowledge protocol for a non-trivial language (i.e., for a language outside $\BPP$), whose security is proven via black-box simulation, must use at least $\tilde\Omega(\log n)$ rounds of interaction. This result achieves a substantial improvement over previous lower bounds, and is the first bound to rule out the possibility of constant-round concurrent zero-knowledge when proven via black-box simulation. Furthermore, the bound is polynomially related to the number of rounds in the best known concurrent zero-knowledge protocol for languages in $\NP$.

Category / Keywords: cryptographic protocols / zero-knowledge

Publication Info: An extended abstract to appear in STOC01

Date: received 24 Jun 2001

Contact author: alon at wisdom weizmann ac il

Available format(s): Postscript (PS) | Compressed Postscript (PS.GZ) | BibTeX Citation

Version: 20010624:193949 (All versions of this report)

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