Deciding Irreducibility/Indecomposability of Feedback Shift Registers Is NP-Hard

Feedback shift registers (FSRs) are used as a fundamental component in electronics and confidential communication. A FSR f is said to be reducible if all the output sequences of another FSR g can also be generated by f and the FSR g costs less memory than f. A FSR is said to be decomposable if it ha...

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Main Author: Lin Wang
Format: Article
Language:English
Published: Hindawi-IET 2024-01-01
Series:IET Information Security
Online Access:http://dx.doi.org/10.1049/2024/3219604
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author Lin Wang
author_facet Lin Wang
author_sort Lin Wang
collection DOAJ
description Feedback shift registers (FSRs) are used as a fundamental component in electronics and confidential communication. A FSR f is said to be reducible if all the output sequences of another FSR g can also be generated by f and the FSR g costs less memory than f. A FSR is said to be decomposable if it has the same set of output sequences as a cascade connection of two FSRs. Two polynomial-time computable transformations from Boolean circuits to FSRs are proposed such that the output FSR of the first (resp. second) transformation is irreducible (resp. indecomposable) if and only if the input Boolean circuit is satisfiable. Through the two transformations, it is proved that deciding irreducibility (indecomposability) of FSRs is NP-hard. Additionally, FSRs are constructed to show that there exist infinitely many irreducible (resp. indecomposable) FSRs which are decomposable (resp. reducible).
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spelling doaj.art-cc15cb6aa13145c68f11dd9f4a3e4bdd2024-03-15T00:00:03ZengHindawi-IETIET Information Security1751-87172024-01-01202410.1049/2024/3219604Deciding Irreducibility/Indecomposability of Feedback Shift Registers Is NP-HardLin Wang0Science and Technology on Communication Security LaboratoryFeedback shift registers (FSRs) are used as a fundamental component in electronics and confidential communication. A FSR f is said to be reducible if all the output sequences of another FSR g can also be generated by f and the FSR g costs less memory than f. A FSR is said to be decomposable if it has the same set of output sequences as a cascade connection of two FSRs. Two polynomial-time computable transformations from Boolean circuits to FSRs are proposed such that the output FSR of the first (resp. second) transformation is irreducible (resp. indecomposable) if and only if the input Boolean circuit is satisfiable. Through the two transformations, it is proved that deciding irreducibility (indecomposability) of FSRs is NP-hard. Additionally, FSRs are constructed to show that there exist infinitely many irreducible (resp. indecomposable) FSRs which are decomposable (resp. reducible).http://dx.doi.org/10.1049/2024/3219604
spellingShingle Lin Wang
Deciding Irreducibility/Indecomposability of Feedback Shift Registers Is NP-Hard
IET Information Security
title Deciding Irreducibility/Indecomposability of Feedback Shift Registers Is NP-Hard
title_full Deciding Irreducibility/Indecomposability of Feedback Shift Registers Is NP-Hard
title_fullStr Deciding Irreducibility/Indecomposability of Feedback Shift Registers Is NP-Hard
title_full_unstemmed Deciding Irreducibility/Indecomposability of Feedback Shift Registers Is NP-Hard
title_short Deciding Irreducibility/Indecomposability of Feedback Shift Registers Is NP-Hard
title_sort deciding irreducibility indecomposability of feedback shift registers is np hard
url http://dx.doi.org/10.1049/2024/3219604
work_keys_str_mv AT linwang decidingirreducibilityindecomposabilityoffeedbackshiftregistersisnphard