Determining the linear equivalent of NLFFS by using cyclotomic cose

Abstract

Any given periodic sequence can be generated by a family of linear feedback shift registers (LFSR ) . The member of this family with least number of stages is called the linear equivalent of the given periodic sequence. Nonlinear logic (multiplication ofachosen number of bits and modulo 2 addition of the resultant), when applied to the LFSR sequences gives an output sequence called the nonlinear feedforward sequence (NLFFS) with increased complexity . The problem of finding the complexity (linear equivalent) of NLFFS has been studied by using cyclotomic costs for the case when feedback is a primitive polynomial.