We present two applications of resettably-sound zero-knowledge arguments. First, we construct resettable zero-knowledge arguments of knowledge for NP, using a natural relaxation of the definition of arguments (and proofs) of knowledge. We note that, under the standard definition of proofs of knowledge, it is impossible to obtain resettable zero-knowledge arguments of knowledge for languages outside BPP. Second, we construct a constant-round resettable zero-knowledge argument for NP in the public-key model, under the assumption that collision-resistant hash functions exist. This improves upon the sub-exponential hardness assumption required by previous constructions.
We emphasize that our results use non-black-box zero-knowledge simulations. Indeed, we show that some of the results are {\em impossible} to achieve using black-box simulations. In particular, only languages in BPP have resettably-sound arguments that are zero-knowledge with respect to black-box simulation.
Category / Keywords: foundations / zero-knowledge, resettable zero-knowledge, resettable soundness, proofs of knowledge, public-key model Publication Info: To appear in 42nd FOCS, 2001. Date: received 7 Aug 2001, last revised 30 Mar 2006 Contact author: lindell at cs biu ac il Available format(s): Postscript (PS) | Compressed Postscript (PS.GZ) | PDF | BibTeX Citation Version: 20060330:110555 (All versions of this report) Short URL: ia.cr/2001/063 Discussion forum: Show discussion | Start new discussion