Proposed Hybrid Technique in Cryptanalysis of Cryptosystem Based on PSO and SA

Abstract

Modern ciphers are one of the more difficult to break cipher systems becausethese ciphers high security, high speed, non - propagation error and difficulty inbreaking it. One of the most important weaknesses of stream cipher is a matching orcorrelation between the output key-stream and the output of shift registers.This work considers new investigation methods for cryptanalysis stream cipherusing ciphertext only attack depending on Particle Swarm Optimization (PSO) forthe automatic extraction for the key. It also introduces a cryptanalysis system basedon PSO with suggestion for enhancement of the performance of PSO, by usingSimulated Annealing (SA). Additionally, it presents a comparison for thecryptanalysis system results that were obtained by the proposed technique, which iscalled Modified PSO (MPSO) with classical PSO and GA. These algorithms can beused for reducing the number of attempts or trials of key space, which are needed toreach to the optimal solution (the exact initial setting of Linear Feedback ShiftRegister (LFSR)),and increase the speed of the search process to find the bestsolution. Based on the obtained results, these algorithms were shown to be effectiveat finding the optimal solution and the MPSO method operates better compared withPSO in the term of time and accuracy. Well known stream cipher systems wereattacked by the two soft computing methods as the cases of study, which are Geffe ,Brȕer and Shrinking stream cipher systems.