TraceBand: Privacy-Preserving Contact Tracing on Low-Power Wristbands

TraceBand is a low-power and versatile wristband for contact tracing during pandemic outbreaks. Running on a 64 MHz Cortex-M4 microprocessor with 256 KB of memory, TraceBand targets a low-cost design. Still, it seamlessly integrates into the smartphone-based tracing, extending the reach and, therefore, the effectiveness of the Exposure Notification protocol by Google and Apple. As the wristband is restricted to Bluetooth Low Energy for tracing and communication, companion devices and gateways serve as synchronization points and allow the device to offload the recorded contacts for an off-device risk analysis or download the information of infected contacts to perform the risk analysis on the device itself. The presented design ensures compatibility from the ground up and tackles occurring challenges due to resource reduction. Evaluations cover the applicability and energy consumption of the Exposure Notification protocol on resource-constrained devices and the on-device identification of risk contacts. The results show that the contact exchange suits battery-driven, resource-constrained devices, as TraceBand requires 2 mAh per day. At the expanse of battery life, up to 5,000,000 risk keys can be checked on the device daily, increasing consumption to roughly 80 mAh for a single day.