About cookies on this site Our websites require some cookies to function properly (required). In addition, other cookies may be used with your consent to analyze site usage, improve the user experience and for advertising. For more information, please review your options. By visiting our website, you agree to our processing of information as described in IBM’sprivacy statement. To provide a smooth navigation, your cookie preferences will be shared across the IBM web domains listed here.
Publication
SIAM Journal on Computing
Paper
Black-box concurrent zero-knowledge requires (almost) logarithmically many rounds
Abstract
We show that any concurrent zero-knowledge protocol for a nontrivial language (i.e., for a language outside BPP), whose security is proven via black-box simulation, must use at least Ω̃(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 (which is established via black-box simulation).