Study Of Boolean Function Construction And Algebraic Attacks On Stream Ciphers

With the booming of personal mobile communication industry and especially with the maturity of wireless communication application in recent years, information security and secrecy gradually are given attention. Stream ciphers, which are depicted as one encryption for one bit, has the advantage over block ciphers on the security and application characteristics. The proposal of a new attack method, i.e. algebraic attack, has a great impact on the design standard of traditional stream ciphers. This paper discussed the algebraic attack in stream ciphers, LiLi-128 stream ciphers system analysis, characteristics of algebraic immune degree and the construction of asymmetric Boolean Functions with highest algebraic immunity.The main consequence obtained are:1.A close study on algebraic attack in stream cipher, especially in the solution method of over determined multi-argument equations was done. It gave the algebraic attack theory and test result of filter generator stream cipher encryption. It also researched the construction of Boolean Functions annihilator in algebraic attack and its application in stream cipher analysis.2.The LILI-128 stream cipher system was studied and meanwhile some attack arithmetic and test results were compared and analyzed systematically. A new effective attack method was proposed to reconstruct filter function of LILI-128 stream cipher by making use of complexity algorithm, image space reconstruction, clustering, nonlinear prediction and chaos synchronization.3. Analyzed the algebraic immune characteristics in algebraic attack.proposed a class of construction of asymmetric Boolean Functions with highest algebraic immunity. Meanwhile encryption characteristic including Humming weight and nonlinearity were analyzed.