We study the Boolean functions f :F2n F2, n = 6r, of the form f (x) = Tr(xd) with d = 22r + 2r + 1 and F2n . Our main result is the characterization of those for which f are bent. We show also that the set of these cubic bent functions contains a subset, which with the constantly zero function forms a vector space of dimension 2r over F2. Further we determine the Walsh spectra of some related quadratic functions, the derivatives of the functions f.
Anne Canteaut, Pascale Charpin, Gohar M. M. Kyureg