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Side Channel Analysis for Reverse Engineering (SCARE) - An Improved Attack Against a Secret A3/A8 GSM Algorithm
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Abstract: | Side-channel analysis has been recognized for several years as a practical and powerful means to reveal secret keys of [publicly known] cryptographic algorithms. Only very recently this kind of cryptanalysis has been applied to reverse engineer a non-trivial part of the specification of a proprietary (i.e., secret) algorithm. The target here is no longer the value of secret key but the secret specifications of the cryptographic algorithm itself. In a recent paper, Roman Novak (2003) describes how to recover the value of one (out of two) substitution table of a secret instance of the A3/A8 algorithm, the GSM authentication and session-key generation algorithm. His attack presents however two drawbacks from a practical viewpoint. First, in order to retrieve one substitution table ($T_2$), the attacker must know the value of the other substitution table ($T_1$). Second, the attacker must also know the value of secret key $K$. In this paper, we improve Novak's attack and show how to retrieve \emph{both} substitution tables ($T_1$ and $T_2$) \emph{without any prior knowledge about the secret key}. Furthermore, as a side-effect, we also recover the value of the secret key. With this contribution, we intend to present a practical SCARE (Side Channel Analysis for Reverse Engineering) attack, anticipate a growing interest for this new area of side-channel signal exploitation, and remind, if needed, that security cannot be achieved through obscurity alone. |
BibTeX
@misc{eprint-2004-12025, title={Side Channel Analysis for Reverse Engineering (SCARE) - An Improved Attack Against a Secret A3/A8 GSM Algorithm}, booktitle={IACR Eprint archive}, keywords={secret-key cryptography / GSM Authentication, A3/A8, Reverse Engineering, Substitution Table, Side Channel Analysis}, url={http://eprint.iacr.org/2004/049}, note={ christophe.clavier@gemplus.com 12467 received 19 Feb 2004}, author={Christophe Clavier}, year=2004 }