Paper 2017/632

Generalized Polynomial Decomposition for S-boxes with Application to Side-Channel Countermeasures

Dahmun Goudarzi, Matthieu Rivain, Damien Vergnaud, and Srinivas Vivek

Abstract

Masking is a widespread countermeasure to protect implementations of block-ciphers against side-channel attacks. Several masking schemes have been proposed in the literature that rely on the efficient decomposition of the underlying s-box(es). We propose a generalized decomposition method for s-boxes that encompasses several previously proposed methods while providing new trade-offs. It allows to evaluate $n\lambda$-bit to $m\lambda$-bit s-boxes for any integers $n,m,\lambda \geq 1$ by seeing it a sequence of $m$ $n$-variate polynomials over $\mathbb{F_{2^\lambda}}$ and by trying to minimize the number of multiplications over $\mathbb{F_{2^\lambda}}$.