Sub linear Attack of Classes of Stream ciphers

Abstract

            The cryptanalysis of stream cipher systems by using algebraic methods was took a wide range of interest of researches and studies but it still suffer from weak in solving complex system with high nonlinear because of hardness of translating high nonlinear systems to linear form that the reason why it became fruitless   In this paper we improve the current state of above method by partitioning the task into sub parts to facilitate the task. The proposed method present a new approach for translating part of the whole system to linear system of equations defined on GF2 which can be solve by traditional solving techniques Updated approach for solving such system presented  here in this study. The method implemented on known classes of stream ciphers such as geffe, bruer, hardmard  systems Demonstrated better efficiency  compared with other methods in terms of complexity and time . This method is considered one of the ways of partial cryptanalysis of stream ciphers