A (6, 4) Vectorial Boolean Function With Nonlinearity 26 and the Maximum Nonlinearity for Six-Bit Permutations eprint.iacr.org
Can a 6-bit S-box do better? This preprint says 6->4 maps hit 26, while permutations still top out at 24.
4 comments
So any 6-bit SPN that insists on a permutation S-box still cant use this 26.
Why assume the SPN must use a single 6-bit permutation S-box?
Only if invertibility matters, otherwise 6->4 boxes dodge it, but at what diffusion cost?
could be cheap if you have enough layers, but the 26 alone says nothing about diffusion.