A generalized description of DES–based and benes–based permutationgenerators

Abstract

The construction of pseudorandom permutation generators has been of major interest since Luby and Rackoffs first description. Numerous papers have been dedicated to their simplification. Beside the original DES–based further constructions of pseudorandom permutation generators have been introduced. One of these is based on Benes-networks which are well known tools in the field of parallel processing. Up to now both constructions had apparently nothing much in common but their pseudorandomness. In this paper a new type of construction, the Clos–based permutation generator, is introduced. The DES–based and the Benes-based generators are shown to be special cases of this new type. Viewing both as Cles–based generators gives new insights into known results: the original construction of the Benes–based generators can be improved; some of the already known impossibility–results concerning the DES–based generators are now better understandable; finally it is possible, to formulate new necessary conditions for the pseudorandomness of generated permutations.