Abstract:
In cryptographic systems, usually linear feedback shift register based keystream generators are used because of the fact that they can produce sequences with large period, good statistical properties. They are suitable for hardware implementation. Their structure can be analyzed by using algebraic techniques. But a linear feedback shift register by itself can not satisfy high linear complexity property that is required for a keystream generator. One of the methodologies used for destroying the linearity of linear feedback shift registers is to use a nonlinear combining function on the outputs of several linear feedback shift registers. This type of keystream generators is called nonlinear combination generators. In this thesis, a new nonlinear combination generator design named MyBoun is proposed. The main property of MyBoun is resistance against algebraic attacks which is provided by Alternative Bit Search Generator (ABSG) component. It is investigated that MyBoun has all properties of a required keystream generator. It has large period, high linear complexity, good statistical results, high throughput rate, and the characteristic of randomness. MyBoun is designed as a simple hardware oriented, modular keystream generator. Security of MyBoun is analyzed with respect to some known attacks and it is shown that MyBoun has resistance against all those attacks. MyBoun is designed for all applications which need a keystream generator that is secure against attacks, that is easy for hardware implementations, that has characteristic of randomness, good statistical properties, high throughput rate, high period and high linear complexity.
