International Association for Cryptologic Research

International Association
for Cryptologic Research


Paper: Concurrent Zero-Knowledge in Poly-logarithmic Rounds

Joe Kilian
Erez Petrank
Search ePrint
Search Google
Abstract: A proof is concurrent zero-knowledge if it remains zero-knowledge when run in an asynchronous environment, such as the Internet. It is known that zero-knowledge is not necessarily preserved in such an environment; Kilian, Petrank and Rackoff have shown that any {\bf 4} rounds zero-knowledge interactive proof (for a non-trivial language) is not concurrent zero-knowledge. On the other hand, Richardson and Kilian have shown that there exists a concurrent zero-knowledge argument for all languages in NP, but it requires a {\bf polynomial} number of rounds. In this paper, we present a concurrent zero-knowledge proof for all languages in NP with a drastically improved complexity: our proof requires only a poly-logarithmic, specifically, $\omega(\log^2 k)$ number of rounds. Thus, we narrow the huge gap between the known upper and lower bounds on the number of rounds required for a zero-knowledge proof that is robust for asynchronous composition.
  title={Concurrent Zero-Knowledge in Poly-logarithmic Rounds},
  booktitle={IACR Eprint archive},
  keywords={foundations / zero-knowledge},
  note={ 11105 received 24 Apr 2000, revised 28 May 2000},
  author={Joe Kilian and Erez Petrank},