Some Spectral Invariant Operations for Functions with Disjoint Products in the Polynomial Form

Abstract

It has long been known that some transformations of a binary function produce a permutation of some coefficients in the Walsh-Hadamard spectrum or just change the sign of some coefficients. Those operations are known as spectral invariant operations. In this paper some new spectral invariant operations are defined for the functions representable by disjoint quadratic polynomial forms. It is shown that these new invariant operations are useful for characterization of the bent functions.