Cryptology ePrint Archive: Report 2009/011

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

D. Canright and Lejla Batina

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.

Category / Keywords: implementation / AES, S-box, masking, DPA, composite Galois field

Publication Info: ACNS2008, LNCS 5037, pp.446-459, Springer-Verlag

Date: received 5 Jan 2009, last revised 15 Jan 2009

Contact author: dcanright at nps edu

Available format(s): PDF | BibTeX Citation

Note: This is a CORRECTED version of previously published work. The correction fixes a serious security flaw in the original.

Version: 20090115:201855 (All versions of this report)

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