Hardware footprints of S-box in lightweight symmetric block ciphers for IoT and CPS information security systems

The hardware footprint for S-box specification in lightweight block cipher as appropriate to loT and CPS information security systems is presented in this paper. The S-box Boolean function in the lightweight block cipher is defined using the Reed-Muller structure. A Rule Based Common Sub-structure Sharing Optimization (RB-CSSO) algorithm has been proposed towards improving the performance efficiency of Reed-Muller structure. This novel hybrid RB-CSSO optimization mechanism first transforms the direct Positive Polarity Reed Muller (PPRM) S-box representation into Mixed Polarity Reed-Muller (MPRM) S-box architecture using local rule based transformation. Secondly, the Common Sub Term (CST) and Common Sub-expression (CSE) merging/elimination are employed over the resulting MPRM structure. The combined rule-based transformation and the common sub-function sharing demonstrate an overall reduction in area, delay and power of the Reed-Muller S-box structure. Both the theoretical analysis and the experimental verification demonstrate reduction in area and delay of S-box. Post synthesis results based on ASIC standard cell based implementations have been used to analyze area, delay and power values across Process, Voltage and Temperature (PVT) corners for a wide range of operating conditions. Extensive comparisons between direct PPRM and optimized MPRM implementations have been carried out. The post layout simulations of S-box structures realized show the advantages of lower area-delay product, power-area product and power-delay product. This work thus authenticates the application of proposed structure for lightweight, resource constrained security systems. Industry standard full suite of Cadence tools have been employed in the simulations using 65 nm TCBN65GPLUS standard cells of TSMC technology