An energy/security scalable encryption processor using an embedded variable voltage DC/DC converter

Security concerns for battery-operated wireless systems require the development of energy-efficient data-encryption techniques that can adapt to the time-varying data rates and quality-of-service requirements inherent in a wireless application. This work describes the design and implementation of a configurable encryption processor that allows the security provided to be traded off with respect to the energy that is dissipated to encrypt a bit. The processor features an embedded high-efficiency variable-output DC/DC converter that allows the supply voltage to be dynamically varied to match the time-varying throughput and quality requirements of the data stream being encrypted. The resulting processor consumes 134 mW at 2.5 V when encrypting data at a rate of 1 Mb/s using a maximum bit width of 512 bits. The converter efficiency is 96% at the peak load of 134 mW. A comparison of our processor to a software implementation running on a low-power programmable processor shows that our implementation is two to three orders of magnitude more energy efficient.