Lightweight Cryptographic Symmetric Block Ciphers for Smart Internetof Things – Design Considerations and Experimental Insights

The Internet of Things, a rapidly growing revolutionary technology with the potential to transform human lives, promises a future of interconnected smart devices. Smart IoT applications have influenced almost all aspects of life, ranging from trivial to essential and potentially lifesaving. However, security challenges have limited its widespread adoption. Conventional cryptography, though highly secure, is unsuitable for constrained devices due to complex algorithms and high resource requirements. In contrast, lightweight cryptography can unlock the potential of smart IoT by providing an optimal level of security. This paper presents a detailed design rationale for the most popular and widely used lightweight symmetric block ciphers suitable for smart IoT applications. It provides a comprehensive overview of block cipher design principles, including core construction schemes, diffusion and confusion techniques, key scheduling strategies, hardware- and software-specific design approaches, and trade-offs among design and security metrics. Furthermore, it highlights the key aspects of lightweight block cipher design to assist designers and researchers in selecting the most appropriate cipher for specific smart IoT applications. Considering the constraints and varying requirements associated with IoT, nine lightweight block ciphers— Ascon, AES, LBLOCK, Midori, PRESENT, SIMON, SPECK, SIMECK, and SPARX—were implemented on the ARM Cortex-M3-based LPC1768 IoT hardware development platform. These lightweight primitives were evaluated and compared for various design metrics, including memory (RAM/ROM) utilization, execution time, energy, and power consumption, using ULINKpro and ULINKplus debug adapters. The results indicate that the higher evaluation metric values of the AES block cipher underscore the need for lightweight cryptographic primitives that provide optimal security for resource-limited IoT devices. Moreover, the experimental findings guide the selection of lightweight block ciphers tailored to specific IoT applications: SIMECK, SPECK, SIMON, SPARX, Ascon, Midori, and PRESENT for health systems with limited area and high-speed requirements; SIMECK, SPECK, SIMON, SPARX, and Ascon for energy-efficient transportation systems; and SIMECK, SIMON, SPECK, SPARX, and Midori for memory- and processing-constrained smart home devices.