Bent Functions

Then Di is a (2n, 2n−1±2(n−2)/2, 2n−2±2(n−2)/2)-difference set in (Z2)n. Conversely, suppose thatD ⊆ (Z2)n is a (2n, 2n−1±2(n−2)/2, 2n−2±2(n−2)/2)-difference set. Define f ∈ Bn by f(x) = 0 if and only if x ∈ D. Then f is a bent function.