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An equivalence preserving transformation from the Fibonacci to the Galois NLFSRs (0801.4079v2)
Published 28 Jan 2008 in cs.CR
Abstract: Conventional Non-Linear Feedback Shift Registers (NLFSRs) use the Fibonacci configuration in which the value of the first bit is updated according to some non-linear feedback function of previous values of other bits, and each remaining bit repeats the value of its previous bit. We show how to transform the feedback function of a Fibonacci NLFSR into several smaller feedback functions of individual bits. Such a transformation reduces the propagation time, thus increasing the speed of pseudo-random sequence generation. The practical significance of the presented technique is that is makes possible increasing the keystream generation speed of any Fibonacci NLFSR-based stream cipher with no penalty in area.