International Association for Cryptologic Research

International Association
for Cryptologic Research


ConTra Corona: Contact Tracing against the Coronavirus by Bridging the Centralized–Decentralized Divide for Stronger Privacy

Wasilij Beskorovajnov , FZI Research Center for Information Technology
Felix Dörre , Karlsruhe Institute of Technology (KIT)
Gunnar Hartung , Karlsruhe Institute of Technology (KIT)
Alexander Koch , Karlsruhe Institute of Technology (KIT)
Jörn Müller-Quade , Karlsruhe Institute of Technology (KIT)
Thorsten Strufe , Karlsruhe Institute of Technology (KIT)
DOI: 10.1007/978-3-030-92075-3_23
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Presentation: Slides
Conference: ASIACRYPT 2021
Abstract: Contact tracing is among the most important interventions to mitigate the spread of any pandemic usually in the form of manual contact tracing. Smartphone-facilitated digital contact tracing may help to increase tracing capabilities and extend the coverage to those contacts one does not know in person. Most implemented protocols use local Bluetooth Low Energy (BLE) communication to detect contagion-relevant proximity, together with cryptographic protections, as necessary to improve the privacy of the users of such a system. However, current decentralized protocols, including DP3T, do not sufficiently protect infected users from having their status revealed to their contacts, which raises fear of stigmatization. We alleviate this by proposing a new and practical solution with stronger privacy guarantees against active adversaries. It is based on the upload-what-you-observed paradigm, includes a separation of duties on the server side, and a mechanism to ensure that users cannot deduce which encounter caused a warning with high time resolution. Finally, we present a simulation-based security notion of digital contact tracing in the real–ideal setting, and prove the security of our protocol in this framework.
Video from ASIACRYPT 2021
  title={ConTra Corona: Contact Tracing against the Coronavirus by Bridging the Centralized–Decentralized Divide for Stronger Privacy},
  author={Wasilij Beskorovajnov and Felix Dörre and Gunnar Hartung and Alexander Koch and Jörn Müller-Quade and Thorsten Strufe},