Progressive Two-bits Tweak for Linear Redundancy reduction from Finite Field S-Boxes
Athmane Seghier · 2018
The Substitution Box (S-Box) is the most sensitive parameter of the modern block ciphers using only this technique to provide the necessary confusion effect against the linear and differential cryptanalysis. Among these block ciphers; several use the finite field inversion to construct their S-Box(s). However, it was previously demonstrated that any finite field based s-box will possess a complete linear redundancy. This property leads to suspect a certain non-randomness of such S-Boxes. In this paper, a new method based on progressive 2-bits-tweaking is proposed as a solution to reduce or even remove the property of linear redundancy from the coordinates Boolean functions of the tweaked S-Box, with a low impact on the nonlinearity and the differential uniformity.