In this paper, we present three results on bent functions: a construct
ion, a restriction and a characterization. Starting with a single bent
function, in a simple but very effective way, the construction produc
es a large number of new bent functions in the same number of variable
s. The restriction imposes new conditions on tile directional derivati
ves of bent functions. Certain non-existence results that were previou
sly obtained through computer starch follow easily from these conditio
ns. The characterization describes bent functions as certain solutions
of a system of quadratic equations. Interesting new properties of ben
t functions are obtained using the characterization. (C) 1997 Academic
Press.