Introduction

Cryptology is a very active and expanding field tha t brings forward new developments in cryptography and crypt analysis every year. A comprehensive survey and up-to-date report (as of 1988) on the advances in designing ciphers and cryptographic schemes and on recent successes in breaking cryptosystems has been published in [18] as a collection of important papers on cryptology. This special section of the Proceedings of the IEEE, from May 1988, may serve th e interested reader as a first introduction to a variety of topics in contemporary cryptology, ranging from conventional cyptosystems and the Dat a Encryption Standard, over public-key cryptography and recent advances in crypt analysis, to a survey of information authentification. Brassard [1] gives a brief survey of cryptography, which is kept at the nontechnical level. Mathematical concepts in cryptography are emphasised in the books by van Tilborg [19], Patterson [13] and Lidl and Niederreiter [6]. For those interested in details of the design and analysis of ciphers, we refer to the proceedings volumes of the annual meetings EUROCRYPT and CRYPTO, see for example [3] and [14].