On the Security Goals of White-Box Cryptography

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Volume Title
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
Date
2020-03-02
Major/Subject
Mcode
Degree programme
Language
en
Pages
31
327-357
Series
IACR Transactions on Cryptographic Hardware and Embedded Systems, Volume 2020, issue 2
Abstract
We discuss existing and new security notions for white-box cryptography and comment on their suitability for Digital Rights Management and Mobile Payment Applications, the two prevalent use-cases of white-box cryptography. In particular, we put forward indistinguishability for white-box cryptography with hardware-binding (IND-WHW) as a new security notion that we deem central. We also discuss the security property of application-binding and explain the issues faced when defining it as a formal security notion. Based on our proposed notion for hardware-binding, we describe a possible white-box competition setup which assesses white-box implementations w.r.t. hardware-binding. Our proposed competition setup allows us to capture hardware-binding in a practically meaningful way.While some symmetric encryption schemes have been proven to admit plain white-box implementations, we show that not all secure symmetric encryption schemes are white-boxeable in the plain white-box attack scenario, i.e., without hardware-binding. Thus, even strong assumptions such as indistinguishability obfuscation cannot be used to provide secure white-box implementations for arbitrary ciphers. Perhaps surprisingly, our impossibility result does not carry over to the hardware-bound scenario. In particular, Alpirez Bock, Brzuska, Fischlin, Janson and Michiels (ePrint 2019/1014) proved a rather general feasibility result in the hardware-bound model. Equally important, the apparent theoretical distinction between the plain white-box model and the hardware-bound white-box model also translates into practically reduced attack capabilities as we explain in this paper.
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Alpirez Bock , E , Amadori , A , Brzuska , C & Michiels , W 2020 , ' On the Security Goals of White-Box Cryptography ' , IACR Transactions on Cryptographic Hardware and Embedded Systems , vol. 2020 , no. 2 , pp. 327-357 . https://doi.org/10.13154/tches.v2020.i2.327-357