[Resource Topic] 2017/925: Resettably-Sound Resettable Zero Knowledge in Constant Rounds

Welcome to the resource topic for 2017/925

Title:
Resettably-Sound Resettable Zero Knowledge in Constant Rounds

Authors: Wutichai Chongchitmate, Rafail Ostrovsky, Ivan Visconti

Abstract:

In FOCS 2001 Barak et al. conjectured the existence of zero-knowledge arguments that remain secure against resetting provers and resetting verifiers. The conjecture was proven true by Deng et al. in FOCS 2009 under various complexity assumptions and requiring a polynomial number of rounds. Later on in FOCS 2013 Chung et al. improved the assumptions requiring one-way functions only but still with a polynomial number of rounds. In this work we show a constant-round resettably-sound resettable zero-knowledge argument system, therefore improving the round complexity from polynomial to constant. We obtain this result through the following steps. 1. We show an explicit transform from any \ell-round concurrent zero-knowledge argument system into an O(\ell)-round resettable zero-knowledge argument system. The transform is based on techniques proposed by Barak et al. in FOCS 2001 and by Deng et al. in FOCS 2009. Then, we make use of a recent breakthrough presented by Chung et al. in CRYPTO 2015 that solved the longstanding open question of constructing a constant-round concurrent zero-knowledge argument system from plausible polynomial-time hardness assumptions. Starting with their construction \Gamma we obtain a constant-round resettable zero-knowledge argument system \Lambda. 2. We then show that by carefully embedding \Lambda inside \Gamma (i.e., essentially by playing a modification of the construction of Chung et al. against the construction of Chung et al.) we obtain the first constant-round resettably-sound concurrent zero-knowledge argument system \Delta. 3. Finally, we apply a transformation due to Deng et al. to \Delta obtaining a resettably-sound resettable zero-knowledge argument system \Pi, the main result of this work. While our round-preserving transform for resettable zero knowledge requires one-way functions only, both \Lambda, \Delta and \Pi extend the work of Chung et al. and as such they rely on the same assumptions (i.e., families of collision-resistant hash functions, one-way permutations and indistinguishability obfuscation for P/poly, with slightly super-polynomial security).

ePrint: https://eprint.iacr.org/2017/925

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