Contact tracing & privacyThe Challenge of Proximity Apps For COVID-19 Contact Tracing

By Andrew Crocker, Kurt Opsahl, and Bennett Cyphers

Published 15 April 2020

Around the world, a diverse and growing chorus is calling for the use of smartphone proximity technology to fight COVID-19. In particular, public health experts and others argue that smartphones could provide a solution to an urgent need for rapid, widespread contact tracing—that is, tracking who infected people come in contact with as they move through the world. Proponents of this approach point out that many people already own smartphones, which are frequently used to track users’ movements and interactions in the physical world. But it is not a given that smartphone tracking will solve this problem, and the risks it poses to individual privacy and civil liberties are considerable.

Around the world, a diverse and growing chorus is calling for the use of smartphone proximity technology to fight COVID-19. In particular, public health experts and others argue that smartphones could provide a solution to an urgent need for rapid, widespread contact tracing—that is, tracking who infected people come in contact with as they move through the world. Proponents of this approach point out that many people already own smartphones, which are frequently used to track users’ movements and interactions in the physical world.
But it is not a given that smartphone tracking will solve this problem, and the risks it poses to individual privacy and civil liberties are considerableLocation tracking—using GPS and cell site information, for example—is not suited to contact tracing because it will not reliably reveal the close physical interactions that experts say are likely to spread the disease. Instead, developers are rapidly coalescing around applications for proximity tracing, which measures Bluetooth signal strength to determine whether two smartphones were close enough together for their users to transmit the virus. In this approach, if one of the users becomes infected, others whose proximity has been logged by the app could find out, self-quarantine, and seek testing. Just today, Apple and Google announced joint application programming interfaces (APIs) using these principles that will be rolled out in iOS and Android in May. A number of similarly designed applications are now available or will launch soon.

As part of the nearly unprecedented societal response to COVID-19, such apps raise difficult questions about privacy, efficacy, and responsible engineering of technology to advance public health. Above all, we should not trust any application—no matter how well-designed—to solve this crisis or answer all of these questions. Contact tracing applications cannot make up for shortages of effective treatment, personal protective equipment, and rapid testing, among other challenges.