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We study the problem of existence of APN functions of algebraic degree n over {\mathbb F}_{2^{n}} . We characterize such functions by means of derivatives and power moments of the Walsh transform. We deduce several non-existence results which imply, in particular, that for most of the known APN functions F over \mathbb F2^{n} the function x^{2^{n}-1}+F(x) is not APN, and changing a value of $F$ in a single point then results in non-APN functions. This leads us to conjectures that an APN function modified in one point cannot remain APN and that there exists no APN function of algebraic degree $n$ . [ABSTRACT FROM AUTHOR]

This paper introduces the first found infinite classes of almost perfect nonlinear (APN) polynomials which are not Carlet—Charpin—Zinoviev (CCZ)-equivalent to power functions (at least for some values of the number of variables). These are two classes of APN binomials from F2n to F2n (for n divisible by 3, resp., 4). We prove that these functions are extended affine (EA)-inequivalent to any power function and that they are CCZ-inequivalent to the Gold, Kasami, inverse, and Dobbertin functions when n ≥ 12. This means that for n even they are CCZ-inequivalent to any known APN function. In particular, for n = 12, 20, 24, they are therefore CCZ-inequivalent to any power function. [ABSTRACT FROM AUTHOR]

A method for constructing differentially 4-uniform quadratic hexanomials has been recently introduced by J. Dillon. We give various generalizations of this method and we deduce the constructions of new infinite classes of almost perfect nonlinear quadratic trinomials and hexanomials from F22m to F22m. We check for m = 3 that some of these functions are CCZ-inequivalent to power functions. [ABSTRACT FROM AUTHOR]

New infinite classes of almost bent and almost perfect nonlinear polynomials are constructed. It is shown that they are affine inequivalent to any sum of a power function and an affine function. [ABSTRACT FROM AUTHOR]