Non Abelian Bent Functions

Laurent Poinsot (1)

1 LIPN - Laboratoire d'Informatique de Paris-Nord

Perfect nonlinear functions from a finite group $G$ to another one $H$ are those functions $f: G \rightarrow H$ such that for all nonzero $\alpha \in G$, the derivative $d_{\alpha}f: x \mapsto f(\alpha x) f(x)^{-1}$ is balanced. In the case where both $G$ and $H$ are Abelian groups, $f: G \rightarrow H$ is perfect nonlinear if and only if $f$ is bent {\it i.e.} for all nonprincipal character $\chi$ of $H$, the (discrete) Fourier transform of $\chi \circ f$ has a constant magnitude equals to $|G|$. In this paper, using the theory of linear representations, we exhibit similar bentness-like characterizations in the cases where $G$ and/or $H$ are (finite) non Abelian groups. Thus we extend the concept of bent functions to the framework of non Abelian groups.

Mots clés: Bent functions; perfect nonlinearity; finite non Abelian groups; Fourier transform

Domaines: Cryptographie et sécurité [cs.CR]; Théorie des représentations [math.RT]

Laurent Poinsot. Non Abelian Bent Functions. Cryptography and Communications - Discrete Structures, Boolean Functions and Sequences , 2012, 4 (1), pp.1-23. ⟨10.1007/s12095-011-0058-y⟩. ⟨hal-00548008⟩