The editing generator and its cryptanalysis

In this paper, we present a new pseudo-random sequence generator, constructed by using two ternary linear feedback shift registers (LFSR). This new generator is called an editing generator which is a combined model of the clock-control generator (viewed as insertion) and the shrinking generator (viewed as deletion). It is shown that the editing generator has good properties of randomness, such as large periods, high linear spans, large ratio of linear span per symbol and small bias of occurrences of symbols. It is known that clock-control generators and shrinking generators are both insecure. These attacks work only for a single model based stream cipher. Thus, our combined model is secure against these attacks. We devise two different attacks for recovering the initial states of the two LFSRs, i.e., the parity-check attack and the unconstraint embedding attack (analogous to the binary case). Both of these two attacks have exponential running time. It follows that the security is not affected.