On the universal hash functions in Luby-Rackoff Cipher

Abstract

It is known that a super-pseudorandom permutation on 2n bits can be obtained from a random function f on n bits and two bisymmetric and AXU hash functions h1 and h2 on n bits. It has a Feistel type structure which is usually denoted by φ(h1,f,f,h2). Bi-symmetric and AXU hash functions h1,h2 are much weaker primitives than a random function f and they can be computed much faster than random functions. This paper shows that we can further weaken the condition on h1. © Springer-Verlag Berlin Heidelberg 2003.