We present the first non-black-box simulation technique that does not rely on Barak's technique (or on nonstandard assumptions). Invoking this technique, we obtain new and improved protocols resilient to various resetting attacks. These improvements include weaker computational assumptions and better round complexity.
A prominent feature of our technique is its compatibility with rewinding techniques from classic black-box zero-knowledge protocols. The combination of rewinding with non-black-box simulation has proven instrumental in coping with challenging goals as: simultaneously-resettable zero-knowledge, proofs of knowledge, and resettable-security from one-way functions. While previous works required tailored modifications to Barak's technique, we give a general recipe for combining our technique with rewinding. This yields simplified resettable protocols in the above settings, as well as improvements in round complexity and required computational assumptions.
The main ingredient in our technique is a new impossibility result for general program obfuscation. The results extend the impossibility result of Barak et al. (CRYPTO 2001) to the case of obfuscation with approximate functionality; thus, settling a question left open by Barak et al.. In the converse direction, we show a generic transformation from any resettably-sound zero-knowledge protocol to a family of functions that cannot be obfuscated.Category / Keywords: obfuscation, zero-knowledge, resettable-security, knowledge-extraction Original Publication (in the same form): To be published in SICOMP special issue for FOCS 12' Date: received 22 Apr 2015 Contact author: nirbitan at csail mit edu Available format(s): PDF | BibTeX Citation Version: 20150423:131434 (All versions of this report) Short URL: ia.cr/2015/369 Discussion forum: Show discussion | Start new discussion