Cascade Jump Controlled Sequence Generator

Introduction Linear feedback shift registers (LFSR) are known to allow fast implementation and produce sequences with large period and good statistical properties (if the feedback polynomial is chosen appropriately). But inherent linearity of these sequences results in susceptibility to algebraic attacks. That is the prime reason why LFSR's are not used directly for key-stream generation. A well-known method for increasing the linear complexity preserving at the same time a large period and good statistical properties, is to apply clock control, i.e. to irregularly step the LFSR through successive states. Key-stream generators based on regularly clocked LFSR's are susceptible to basic and fast correlation attacks. Using irregular clocking reduces the danger from correlation attacks and provides practical immunity against fast correlation attacks. Due to the multiple clocking, key stream generators that use clock-controlled LFSRs have decreased rate of sequence generation since such