The Impossibility of Obfuscation with Auxiliary Input or a Universal Simulator.

In this paper we show that indistinguishability obfuscation for general circuits implies, somewhat counterintuitively, strong impossibility results for virtual black box obfuscation. In particular, it implies: The impossibility of average-case virtual black box obfuscation with auxiliary input for any circuit family with super-polynomial pseudo-entropy (for example, many cryptographic primitives). Impossibility holds even when the auxiliary input depends only on the public circuit family, and not which circuit in the family is being obfuscated. The impossibility of average-case virtual black box obfuscation with a universal simulator (with or without any auxiliary input) for any circuit family with super-polynomial pseudo-entropy. These bounds significantly strengthen the impossibility results of Gold-wasser and Kalai (FOCS 2005).