Paper 2020/1473 Original: eprint.iacr.org/2020/1473 ↗

Lighthouses: A Warning System for Super-Spreader Events

Abstract

Super-spreader events where one person infects many others have been a driving force of the Covid-19 pandemic. Such events often happen indoors, such as in restaurants, at choir practice or in gyms. Many systems for automated contact tracing (ACT) have been proposed, which will warn a user when they have been in proximity to an infected person. These generally fail to detect potential super-spreader events as only users who have come in close contact with the infected person, but not others who also visited the same location, are warned. Other approaches allow users to check into locations or venues, but these require user interaction. We propose two designs how broadcast-based ACT systems can be enhanced to utilize location-specific information without the need for GPS traces or scanning of QR codes. This makes it possible to alert attendees of a potential super-spreader event while still remaining private. Our first design relies on cooperating lighthouses which cover a large area and send out pseudonyms. These are recorded by visitors and published by the health authority (HA) in case of an infection. The second design has lighthouses actively communicating with HAs after retrospectively detecting an infected visitor to warn everyone whose stay overlapped.