Computational Intelligence in Cryptology

Abstract

Computational intelligence (CI) has attracted the attention of many researchers for its effectiveness in solving different kinds of problems. It has been applied to solve problems in a wide area of applications. The aim of this chapter is to present an overview of existing literature about the applications of CI in cryptology. It demonstrates and studies the applicability of CI in cryptology. The problems examined in this chapter are the automated design of cipher systems, and the automated cryptanalysis of cipher systems. It has been shown that CI methods, such as genetic algorithms, genetic programming, Tabu search, and memetic computing are effective tools to solve most of cryptology problems.

An Improved Genetic Algorithm and A New Discrete Cuckoo Algorithm for Solving the Classical Substitution Cipher

“…Fordeterminingsecretkey,theautomatedattackstrategymayusejusttheknownciphertexts (i.e.,encryptedplaintexts),someplaintexts,andintelligentalgorithms.Iftheattacker(orcryptanalyst) recoverthesecretkeybyusingthe"knownciphertexts"only,thenthiskindofattackisreferredas aciphertext-onlyattack (Menezesetal.,1996;Stinson,2005;Holden,2017).Thistypeofattack is most demanding and challenging, therefore, in this work, we demonstrate such attacks using metaheuristic techniques. For a systematic demonstration of automated attacks, the well-known classicalsubstitutioncipherisconsidered.Onecanaskwhymodernciphersarenotconsideredto demonstratemetaheuristicattacks.Thefactisthatmetaheuristicscannotbeappliedtoattackmodern ciphers such as DES (data encryption standard), AES (advanced encryption standard), and RSA (Rivest-Shamir-Adleman),becauseunsuitabilityindesigningthefitnessfunctionformodernciphers (Castro and Viñuela, 2005;Danziger and Henriques, 2012;Awad and El-Alfy, 2015). However, cryptanalysisofclassicalciphers(anNP-completeproblem)canbecarriedoutusingmetaheuristics becausethefitnessfunctioncanbewell-designedbyusingexpectedandobservedn-gramstatistics ofthelanguage (CastroandViñuela,2005;DanzigerandHenriques,2012;AwadandEl-Alfy,2015).…”