  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.
