Cryptology ePrint Archive: Report 2015/383

Impossibility of VBB Obfuscation with Ideal Constant-Degree Graded Encodings

Rafael Pass and abhi shelat

Abstract: A celebrated result by Barak et al (JACM’12) shows the impossibility of general-purpose virtual black-box (VBB) obfuscation in the plain model. A recent work by Canetti, Kalai, and Paneth (TCC’15) extends this result also to the random oracle model (assuming trapdoor per- mutations).

In contrast, Brakerski-Rothblum (TCC’15) and Barak et al (EuroCrypt’14) show that in idealized graded encoding models, general-purpose VBB obfuscation indeed is possible; these construction require graded encoding schemes that enable evaluating high-degree (polynomial in the size of the circuit to be obfuscated) polynomials on encodings. We show a complementary impossibility of general-purpose VBB obfuscation in idealized graded encoding models that enable only evaluation of constant-degree polynomials (assuming trapdoor permutations).

Category / Keywords: foundations / VBB obfuscation, graded encodings

Date: received 24 Apr 2015

Contact author: rafael at cs cornell edu

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Version: 20150428:235619 (All versions of this report)

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