Limits on the Power of Indistinguishability Obfuscation and Functional

Research output: Contribution to journalArticlepeer-review


Recent breakthroughs in cryptography have positioned indistinguishability obfuscation as a ``central hub'' for almost all known cryptographic tasks, and as an extremely powerful building block for new cryptographic tasks resolving long-standing and foundational open problems. However, constructions based on indistinguishability obfuscation almost always rely on non-black-box techniques, and thus the extent to which it can be used as a building block has been completely unexplored so far.

We present a framework for proving meaningful negative results on the power of indistinguishability obfuscation. By considering indistinguishability obfuscation for oracle-aided circuits, we capture the common techniques that have been used so far in constructions based on indistinguishability obfuscation. These include, in particular, non-black-box techniques such as the punctured programming approach of Sahai and Waters (STOC '14) and its variants, as well as sub-exponential security assumptions.

Within our framework we prove the first negative results on the power of indistinguishability obfuscation and of the tightly related notion of functional encryption. Our results are as follows:

-- There is no fully black-box construction of a collision-resistant function family from an indistinguishability obfuscator for oracle-aided circuits.

-- There is no fully black-box construction of a key-agreement protocol with perfect completeness from a private-key functional encryption scheme for oracle-aided circuits.

Specifically, we prove that any such potential constructions must suffer from an exponential security loss, and thus our results cannot be circumvented using sub-exponential security assumptions. Our framework captures constructions that may rely on a wide variety of primitives in a non-black-box manner (e.g., obfuscating or generating a functional key for a function that uses the evaluation circuit of a puncturable pseudorandom function), and we only assume that the underlying indistinguishability obfuscator or functional encryption scheme themselves are used in a black-box manner.
Original languageEnglish
Article number2015/341
Number of pages63
JournalIACR Cryptology ePrint Archive,
StatePublished - 2015


Dive into the research topics of 'Limits on the Power of Indistinguishability Obfuscation and Functional'. Together they form a unique fingerprint.

Cite this