Bent partitions and Maiorana-McFarland association schemes

Official URL: https://dx.doi.org/10.1007/s12095-025-00801-x

The recently introduced generalized semifield spreads are partitions of Fpm×Fpm, which are constructed from presemifields with a certain property, called right Fpk-linearity. These partitions have similar properties as spreads. In particular, they are bent partitions, hence they yield a large number of bent functions, vectorial bent functions and amorphic association schemes. We show that with a slight change of parameters, we obtain inequivalent bent partitions, non-isomorphic divisible designs, and bent functions with various algebraic degrees. This is in contrast to classical spreads of Fpm×Fpm, which yield bent functions all of which have algebraic degree (p-1)m. We show that with right Fpk-linear presemifields we can obtain a large variety of vectorial dual-bent functions, which yield, not necessarily amorphic, association schemes. We investigate fusions of these association schemes, which reveal information on their inner structure, and may provide a tool to distinguish non-isomorphic association schemes.