[Resource Topic] 2015/1023: Indistinguishability Obfuscation for Turing Machines: Constant Overhead and Amortization

Welcome to the resource topic for 2015/1023

Title:
Indistinguishability Obfuscation for Turing Machines: Constant Overhead and Amortization

Authors: Prabhanjan Ananth, Abhishek Jain, Amit Sahai

Abstract:

We study the asymptotic efficiency of indistinguishability obfuscation (iO) on two fronts: - Obfuscation size: Present constructions of indistinguishability obfuscation (iO) create obfuscated programs where the size of the obfuscated program is at least a multiplicative factor of security parameter larger than the size of the original program. In this work, we construct the first iO scheme for (bounded-input) Turing machines that achieves only a constant multiplicative overhead in size. The constant in our scheme is, in fact, 2. - Amortization: Suppose we want to obfuscate an arbitrary polynomial number of (bounded-input) Turing machines M_1,…,M_n. We ask whether it is possible to obfuscate M_1,…,M_n using a single application of an iO scheme for a circuit family where the size of any circuit is independent of n as well the size of any Turing machine M_i. In this work, we resolve this question in the affirmative, obtaining a new bootstrapping theorem for obfuscating arbitrarily many Turing machines. Our results rely on the existence of sub-exponentially secure iO for circuits and re-randomizable encryption schemes. In order to obtain these results, we develop a new template for obfuscating Turing machines that is of independent interest and has recently found application in subsequent work on patchable obfuscation [Ananth et al, EUROCRYPT’17].

ePrint: https://eprint.iacr.org/2015/1023

Talk: https://www.youtube.com/watch?v=B20V45eeAFU

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