Difference Methods and Ferrero Pairs

We present a construction method of BIB-designs from a finite group G and a group of automorphisms \Phi on G such that |\Phi(x)| = |\Phi| for all x in G, x <> 0. By using a generalization of the concept of a difference family we can so unify several previous constructions of BIB-designs from planar near-rings.