Friday, November 16, 2007 



New Nonlinear Functions for SBoxes in Cryptography and their Fourier Transform 

Functions used in SBoxes in block ciphers are required to be highly
nonlinear in order to be resistant to linear cryptanalysis. This
property is related to the Fourier spectrum of the function. The
functions are also required to be resistant to differential cryptanalysis, and
functions providing optimal resistance here are called perfect nonlinear. The two
properties are different but curiously related. Few examples of these functions are
known. 