International Association for Cryptologic Research

International Association
for Cryptologic Research

CryptoDB

Paper: Side Channel Analysis for Reverse Engineering (SCARE) - An Improved Attack Against a Secret A3/A8 GSM Algorithm

Authors:
Christophe Clavier
Download:
URL: http://eprint.iacr.org/2004/049
Search ePrint
Search Google
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
}