International Association for Cryptologic Research

International Association
for Cryptologic Research


Paper: A Very Compact "Perfectly Masked" S-Box for AES (corrected)

D. Canright
Lejla Batina
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Abstract: Implementations of the Advanced Encryption Standard (AES), including hardware applications with limited resources (e.g., smart cards), may be vulnerable to "side-channel attacks" such as differential power analysis. One countermeasure against such attacks is adding a random mask to the data; this randomizes the statistics of the calculation at the cost of computing "mask corrections." The single nonlinear step in each AES round is the "S-box" (involving a Galois inversion), which incurs the majority of the cost for mask corrections. Oswald et al. showed how the "tower field" representation allows maintaining an additive mask throughout the Galois inverse calculation. This work applies a similar masking strategy to the most compact (unmasked) S-box to date. The result is the most compact masked S-box so far, with "perfect masking" (by the definition of Blomer) giving suitable implementations immunity to first-order differential side-channel attacks.
  title={A Very Compact "Perfectly Masked" S-Box for AES (corrected)},
  booktitle={IACR Eprint archive},
  keywords={implementation / AES, S-box, masking, DPA, composite Galois field},
  note={ACNS2008, LNCS 5037, pp.446-459, Springer-Verlag 14259 received 5 Jan 2009, last revised 15 Jan 2009},
  author={D. Canright and Lejla Batina},