Journal of Theoretical and Applied Information Technology © 2005 - 2009 JATIT. All rights reserved. www.jatit.org 387 GENETIC ALGORITHMS, TABU SEARCH AND SIMULATED ANNEALING: A COMPARISON BETWEEN THREE APPROACHES FOR THE CRYPTANALYSIS OF TRANSPOSITION CIPHER POONAM GARG Institute of Management Technology, INDIA E-mail: pgarg@imt.edu ABSTRACT: Due to increasing incidents of cyber attacks, the demand for effective internet security is increasing. Cryptology is the science and study of systems for secret communication. It consists of two complementary fields of study: cryptography and cryptanalysis. In this paper, we propose a cryptanalysis method based on genetic algorithm, tabu search & simulated annealing to break a transposition cipher. We will also compare and analyze the performance of these algorithms in automated attacks on a transposition cipher. A generalized version of these algorithms can be used for attacking other cipher as well. Keywords: Transposition Cipher, Genetic Algorithm, Tabu Search, Simulated Annealing, Key search. 1. INTRODUCTION The demand for effective internet security is increasing exponentially day by day. Businesses have an obligation to protect sensitive data from loss or theft. Such sensitive data can be potentially damaging if it is altered, destroyed, or if it falls into the wrong hands. So they need to develop a scheme that guarantees to protect the information from the attacker. Cryptology is at the heart of providing such guarantee. Cryptology is the science of building and analyzing different encryption and decryption methods. Cryptology consists of two subfields; Cryptography & Cryptanalysis. Cryptography is the science of building new powerful and efficient encryption and decryption methods. It deals with the techniques for conveying information securely. The basic aim of cryptography is to allow the intended recipients of a message to receive the message properly while preventing eavesdroppers from understanding the message. Cryptanalysis is the science and study of method of breaking cryptographic techniques i.e. ciphers. In other words it can be described as the process of searching for flaws or oversights in the design of ciphers. Classical ciphers fall into one of the two broad categories: substitution cipher & transposition cipher. Modern crypto-systems have now supplanted the classical ciphers but cryptanalysis of classical ciphers is most popular crypto logical application for meta-heuristic search research. The basic concepts of substitution and transposition are still widely used today in the Advanced Encryption Standard(AES). Advanced Encryption Standards(AES) & International Data Encryption Algorithm (IDEA) are widely used encryption algorithm which use only three very simple operators, namely substitution, permutation(transposition) and bit-wise exclusive- OR operator. Since the operations of the classical cipher are the building blocks of modern ciphers, so the classical ciphers are usually the first ones considered when researching new attacks. Transposition cipher simply performs some permutation over the plain text alphabet. Transposition cipher works by breaking a message into fixed size blocks, and then permuting the characters within each block according to a fixed permutation; say ∏ the key to the transposition cipher is simply the permutation ∏ . The transposition cipher has the property that the encrypted message (i.e., the ciphertext) contains all the characters that were in the plaintext message, albeit in a different (and hopefully meaningless) order. Example of the transposition cipher is presented in Table 1.