On the (Im)possibility of Obfuscating Programs

Webpage for a paper by Boaz Barak, Oded Goldreich, Rusell Impagliazzo, Steven Rudich, Amit Sahai, Salil Vadhan, and Ke Yang

Abstract

In this work, we initiate a theoretical investigation of obfuscation. Our main result is that, even under very weak formalizations of the above intuition, obfuscation is impossible. We prove this by constructing a family of functions F that are inherently unobfuscatable in the following sense: there is a predicate pi such that (a) given any program that computes a function f in F, the value pi(f) can be efficiently computed, yet (b) given oracle access to a (randomly selected) function f in F, no efficient algorithm can compute pi(f) much better than random guessing.

We extend our impossibility result in a number of ways, including even obfuscators that (a) are not necessarily computable in polynomial time, (b) only approximately preserve the functionality, and (c) only need to work for very restricted models of computation TC0). We also rule out several potential applications of obfuscators, by constructing ``unobfuscatable'' signature schemes, encryption schemes, and pseudorandom function families.

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