International Association for Cryptologic Research

International Association
for Cryptologic Research

IACR News item: 28 April 2015

Rafael Pass, abhi shelat
ePrint Report ePrint Report
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).

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