Comparison of hardware and software implementations of selected lightweight block ciphers

Abstract

Lightweight block ciphers are an important topic of research in the context of the Internet of Things (IoT). Current cryptographic contests and standardization efforts seek to benchmark lightweight ciphers in both hardware and software. Although there have been several benchmarking studies of both hardware and software implementations of lightweight ciphers, direct comparison of hardware and software implementations is difficult due to differences in metrics, measures of effectiveness, and implementation platforms. In this research, we facilitate this comparison by use of a custom lightweight reconfigurable processor. We implement six ciphers, AES, SIMON, SPECK, PRESENT, LED and TWINE, in hardware using register transfer level (RTL) design, and in software using the custom reconfigurable processor. Both hardware and software implementations are instantiated in identical Xilinx Kintex-7 FPGAs, which enables direct comparison of throughput, area, throughput-to-area (TP/A) ratio, power, and energy. Results show that TWINE and AES have the highest TP/A ratios for hardware and software implementations, respectively, assuming an area target of 300–450 LUTs. In terms of direct comparison, software implementations on tailored reconfigurable processers generally use less power — especially where reconfigurable instruction set extensions are permitted. However, custom hardware implementations have higher throughput and energy-efficiency than software implementations on the same platform.