Cryptology ePrint Archive: Report 2018/397

Cryptanalysis on the HHSS Obfuscation Arising from Absence of Safeguards

Jung Hee Cheon and Minki Hhan and Jiseung Kim and Changmin Lee

Abstract: Indistinguishability Obfuscation (iO) is a hopeful tool which obfuscates a program with the least-possible leakage, and produces various applications including functional encryption and deniable encryption. Recently, Halevi et. al. proposed a state-of-the-art obfuscator implementation, called HHSS obfuscation, in ACM-CCS'17.

In this work, we describe a polynomial time distinguishing attack on HHSS obfuscation. In other words, we show that there exist two functionally equivalent branching programs but obfuscated programs are actually distinguishable. This attack implies that HHSS obfuscation fails to achieve a general purpose of iO security. The idea of the attack is quite simple; we multiply a left kernel vector of the branching program P to an evaluation of obfuscated matrix, which yields a small value when the program P is obfuscated. Our attack algorithm is also applicable even if evasive functions are obfuscated.

Category / Keywords: graded encoding scheme, indistinguishability obfuscation

Date: received 18 Apr 2018, last revised 13 May 2018

Contact author: tory154 at snu ac kr

Available format(s): PDF | BibTeX Citation

Note: Revise several parts

Version: 20180514:013702 (All versions of this report)

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