Feistel type authentication codes

Abstract

In this paper we generalise Luby-ttackoff construction of pseudorandom permutation generators to generalised invertible function generators and prove that if there exits a generalised pseudorandom function generator then there exist a generalised pseudorandom invertible generator. This construction is then used for a pseudorandom authentication code which offers provable security against T-fold chosen plaintext/ ciphertext attack and provable perfect protection against strong spoofing of order T. The performance of the code is compared with that of a code obtained from a Feistel type permutation generator. The code, called Feistel type A-code, provides a new approach to the design of practically good A-codes and hence is of high practical significance.