A ring-like cascade connection and a class of NFSRs with the same cycle structures
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Nonlinear feedback shift registers (NFSRs) are widely used in stream cipher designs. In this paper, we propose a variant of cascade connections of NFSRs, called ring-like cascade connections. It is shown that given an initial state of a ring-like cascade connection, each register outputs the sequence of the same period. Based on this configuration, a class of NFSRs with the same cycle structure can be derived. Moreover, inspired by this result, two more general types of NFSRs with the same cycle structures are also studied.
KeywordsStream ciphers Nonlinear feedback shift registers Cycle structure Cascade connection
Mathematics Subject Classification11B50 94A55 94A60
This work was supported by the National Natural Science Foundation of China (Grant Nos. 61672533, 61521003) and the National Cryptography Development Fund of China (Grant No. MMJJ20170103).
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