New family of Stream Ciphers and their applications for Physical Security
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In this paper, we propose a new family of stream ciphers based on combining selected sets of Nonlinear Feedback Shift Registers (NLFSRs) with maximum periods. All stream ciphers from this family share the same security level and have a linear complexity exceeding 2^81. The design strategy is based on defining NLFSRs feedback functions from sets of selected boolean functions that ensure the same maximum period. We propose to deploy this family of stream ciphers for creating Secret Unknown Ciphers (SUCs). SUC is a random unpredictable and unknown cipher that is self-generated internally in a SoC FPGA to ensure unique and consistent digital identity for each unit. SUC was presented recently to overcome the drawbacks of the traditional analog Physically Unclonable Functions (PUFs). This work presents a lightweight identification protocol for physically identifying units incorporating such SUCs as clone-resistant System-on-Chip (SoC) entities in open networks. The proposed new family of stream ciphers is a lightweight realization of SUC optimized for modern SoC FPGAs. Security analysis and hardware complexity of the resulting SUC structures are evaluated.
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