  The control of the COVID-19 pandemic requires a considerable reduction of
contacts mostly achieved by imposing movement control up to the level of
enforced quarantine. This has lead to a collapse of substantial parts of the
economy. Carriers of the disease are infectious roughly 3 days after exposure
to the virus. First symptoms occur later or not at all. As a consequence
tracing the contacts of people identified as carriers is essential for
controlling the pandemic. This tracing must work everywhere, in particular
indoors, where people are closest to each other. Furthermore, it should respect
people's privacy. The present paper presents a method to enable a thorough
traceability with very little risk on privacy. In our opinion, the latter
capabilities are necessary to control the pandemic during a future relaunch of
our economy.
