International Association for Cryptologic Research

International Association
for Cryptologic Research


Paper: Impossibility of Quantum Virtual Black-Box Obfuscation of Classical Circuits

Gorjan Alagic , QuICS, University of Maryland & National Institute of Standards and Technology
Zvika Brakerski , Weizmann Institute of Science
Yfke Dulek , QuSoft & Centrum Wiskunde en Informatica
Christian Schaffner , QuSoft & University of Amsterdam
DOI: 10.1007/978-3-030-84242-0_18 (login may be required)
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Conference: CRYPTO 2021
Abstract: Virtual black-box obfuscation is a strong cryptographic primitive: it encrypts a circuit while maintaining its full input/output functionality. A remarkable result by Barak et al. (Crypto 2001) shows that a general obfuscator that obfuscates classical circuits into classical circuits cannot exist. A promising direction that circumvents this impossibility result is to obfuscate classical circuits into quantum states, which would potentially be better capable of hiding information about the obfuscated circuit. We show that, under the assumption that Learning With Errors (LWE) is hard for quantum computers, this quantum variant of virtual black-box obfuscation of classical circuits is generally impossible. On the way, we show that under the presence of dependent classical auxiliary input, even the small class of classical point functions cannot be quantum virtual black-box obfuscated.
Video from CRYPTO 2021
  title={Impossibility of Quantum Virtual Black-Box Obfuscation of Classical Circuits},
  author={Gorjan Alagic and Zvika Brakerski and Yfke Dulek and Christian Schaffner},