Think Before Your LFSRs Jump

摘要

This paper scrutinizes the structure of jump-controlled LFSRs for resistance against generalized correlation attack based upon Constrained Levenshtein Distance(CLD) measure. It proves that for a given number of cipher text bits, CLD computation is independent of Jump index. However, based upon the inherent relation between the jump index and deletion rate, it is argued that structures utilizing primitive polynomials with large values of jump indices are relatively safer against generalized correlation attack when compared with their counterparts. The paper also presents a novel recursive algorithm for efficient computation of CLD for jump controlled structures and another algorithm to defeat the complexity induced due to high deletion rates.