On Almost Perfect Nonlinear Permutations

In this paper basic properties of APN permutations, which can be used in an iterated secret-key block cipher as a round function to protect it from a differential cryptanalysis, are investigated. Several classes of almost perfect nonlinear permutations and other permutations in GF(2)n with good nonlinearity and high nonlinear order are presented. Included here are also three methods for constructing permutations with good nonlinearity.