Differential Spectrum of Kasami Power Permutations Over Odd Characteristic Finite Fields

Functions with low differential uniformity have important applications in cryptography, coding theory, and sequence design. The differential spectrum of a cryptographic function is of great interest for estimating its resistance to some variants of differential cryptanalysis. Finding power permutations (i.e., monomial bijective mappings) over finite fields with low differential uniformity and determining their differential spectra have received a lot of attention over the past two decades. The objective of this paper is to study the differential properties of the well-known Kasami power permutations (x)p(2k-)p(k+ \1) over GF(p(n)), where p is an odd prime and k is an integer with gcd(n, k) = 1. It turns out that this family of monomials is differentially (p + 1)-uniform. Our result in the case of p = 3 gives an affirmative solution to a recent conjecture by Xu, Cao, and Xu. Most notably, the differential spectrum of this family of power permutations is completely determined.