Algebraic attack was applied to attack Filter-Combintr model keystreamgenerators. We proposed the technique of function composition to improve the model, and the improvedmodel can resist the algebraic attack. A new cr...Algebraic attack was applied to attack Filter-Combintr model keystreamgenerators. We proposed the technique of function composition to improve the model, and the improvedmodel can resist the algebraic attack. A new criterion for designing Filter-Combiner model was alsoproposed: the total length I. of Linear Finite State Machines used in the model should be largeenough and the degree d of Filter-Combiner function should be approximate [L/2].展开更多
This letter proposes algebraic attacks on two kinds of nonlinear filter generators with symmetric Boolean functions as the filter fimctions. Different fxom the classical algebraic attacks, the proposed attacks take th...This letter proposes algebraic attacks on two kinds of nonlinear filter generators with symmetric Boolean functions as the filter fimctions. Different fxom the classical algebraic attacks, the proposed attacks take the advantage of the combinational property of a linear feedback shift register （LFSR） and the symmetric Boolean function to obtain a tow-degree algebraic relation, and hence the complexities of the proposed attacks are independent of the algebraic immunity （AI） of the filter functions. It is shown that improper combining of the LFSR with the filter function can make the filter generator suffer from algebraic attacks. As a result, the bits of the LFSR must be selected properly to input the filter function with large AI in order to withstand the proposed algebraic attacks.展开更多
This paper presents a new method for resynchronization attack, which is the combination of the differential cryptanalysis and algebraic attack. By using the new method one gets a system of linear equations or low-degr...This paper presents a new method for resynchronization attack, which is the combination of the differential cryptanalysis and algebraic attack. By using the new method one gets a system of linear equations or low-degree equations about initial keys, and the solution of the system of equations results in the recovery of the initial keys. This method has a lower computational complexity and better performance of attack in contrast to the known methods. Accordingly, the design of the resynchronization stream generators should be reconsidered to make them strong enough to avoid our attacks. When implemented to the Toyocrypt, our method gains the computational complexity of O（2^17）, and that of 0（2^67） for LILI-128.展开更多
文摘Algebraic attack was applied to attack Filter-Combintr model keystreamgenerators. We proposed the technique of function composition to improve the model, and the improvedmodel can resist the algebraic attack. A new criterion for designing Filter-Combiner model was alsoproposed: the total length I. of Linear Finite State Machines used in the model should be largeenough and the degree d of Filter-Combiner function should be approximate [L/2].
基金Supported by the National Basic Research Program of China （No. 2007CB311201）, the National Natural Science Foundation of China （No.60833008 No.60803149）, and the Foundation of Guangxi Key Laboratory of Information and Communication （No.20902）.
文摘This letter proposes algebraic attacks on two kinds of nonlinear filter generators with symmetric Boolean functions as the filter fimctions. Different fxom the classical algebraic attacks, the proposed attacks take the advantage of the combinational property of a linear feedback shift register （LFSR） and the symmetric Boolean function to obtain a tow-degree algebraic relation, and hence the complexities of the proposed attacks are independent of the algebraic immunity （AI） of the filter functions. It is shown that improper combining of the LFSR with the filter function can make the filter generator suffer from algebraic attacks. As a result, the bits of the LFSR must be selected properly to input the filter function with large AI in order to withstand the proposed algebraic attacks.
基金Supported in part by the National Natural Science Foundation of China (No.60273084)the National Laboratory for Modern Communications Foundation of China (No.51436030105DZ0105).
文摘This paper presents a new method for resynchronization attack, which is the combination of the differential cryptanalysis and algebraic attack. By using the new method one gets a system of linear equations or low-degree equations about initial keys, and the solution of the system of equations results in the recovery of the initial keys. This method has a lower computational complexity and better performance of attack in contrast to the known methods. Accordingly, the design of the resynchronization stream generators should be reconsidered to make them strong enough to avoid our attacks. When implemented to the Toyocrypt, our method gains the computational complexity of O（2^17）, and that of 0（2^67） for LILI-128.
