  Businesses planning for the post-pandemic world are looking for innovative
ways to protect the health and welfare of their employees and customers.
Wireless technologies can play a key role in assisting contact tracing to
quickly halt a local infection outbreak and prevent further spread. In this
work, we present a wearable proximity and exposure notification solution based
on a smartwatch that also promotes safe physical distancing in business,
hospitality, or recreational facilities. Our proximity-based privacy-preserving
contact tracing (P$^3$CT) leverages the Bluetooth Low Energy (BLE) technology
for reliable proximity sensing, and an ambient signature protocol for
preserving identity. Proximity sensing exploits the received signal strength
(RSS) to detect the user's interaction and thus classifying them into low- or
high-risk with respect to a patient diagnosed with an infectious disease. More
precisely, a user is notified of their exposure based on their interactions, in
terms of distance and time, with a patient. Our privacy-preserving protocol
uses the ambient signatures to ensure that users' identities be anonymized. We
demonstrate the feasibility of our proposed solution through extensive
experimentation.
