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A Compact, Lightweight and Low-Cost 8-Bit Datapath AES Circuit for IoT Applications in 28nm CMOS

Lightweight AES encryption circuits are significant to IoT applications to protect data, where very strict area and power constraints are required. In this paper, we propose a novel 8-bit datapath AES architecture aiming for a small area and a high energy efficiency. Firstly, our proposed design reduces the number of temporary data storage (IntermediateReg) to 40-bit from the originally 128-bit, which saves 68.75% intermediate registers. Secondly, only one S-Box is implemented in the design that is reused throughout the whole AES operations to achieve a low area. Thirdly, the architecture is further optimized to reduce the number of clock cycles by reusing S-Box in the key expansion and the data encryption module, leading to only 213 total cycles of latency in a complete encryption process. Simulation results under TSMC 28nm technology show that our proposed AES circuit consumes an area of 0.0028mm2, with an energy efficiency of 667Gbps/W (equivalent to 1.50 pJ/bit) and throughput rate of 30.05Mbps at 0.5V. This design achieves a high energy efficiency per unit area of 0.278 Gbps/(W•um2). This small area, high energy efficiency and relatively high throughput AES circuit is suitable for IoT applications.