Lightweight Block Ciphers for IoT: Energy Optimization and Survivability Techniques

With extraordinary growth in the Internet of Things (IoT), the amount of data exchanged between IoT devices is growing at an unprecedented scale. Most of the IoT devices are low-resource devices handling sensitive and confidential data. Conventional encryption methods are inappropriate for lowresource devices. Lightweight block ciphers are used to encrypt data on such devices, as it balances security requirements and energy consumption. The objective of this paper is to explore opportunities to improve performance and optimize energy consumption for cipher designs targeted for low-resource IoT devices. This paper also presents an energy management algorithm to improve IoT survivability against Denial-ofservice attacks in the form of battery exhaustion. We developed a simple and effective model for lightweight cipher performance metrics. Model results were compared and validated with published application-specific integrated circuit (ASIC) and field-programmable gate array (FPGA) designs. Using the model, we explored opportunities for performance enhancement in future cipher designs. Our analysis indicates that the optimum energy is achieved when block size is between 48-bit and 96-bit. Also, increasing size of overhead logic from one round to two rounds increases encryption energy-per-bit by 3.4%. Further, the optimum energy is attained when the number of algorithm rounds is 16 or less. Optimum throughput is achieved by implementations with large block sizes and large number of implemented rounds. Next, we present a novel algorithm to manage cipher energy consumption. The algorithm allows low-resource IoT devices to encrypt critical messages during low-energy mode while balancing throughput, energy per bit, and device activity.