Paper 2020/398

Decentralized Contact Tracing Using a DHT and Blind Signatures

Samuel Brack and Leonie Reichert and Björn Scheuermann

Abstract

Contact tracing is a promising approach to combat the COVID -19 pandemic. Various systems have been proposed to automatise the process. However, user privacy was not a major design goal in most of these systems. Other designs rely heavily on a centralised server or reveal significant amounts of private data to health authorities. We propose CAUDHT, a decentralized peer-to-peer system for contact tracing. The central health authority can focus on providing and operating tests for the disease while contact tracing is done by the system’s users themselves. We use a distributed hash table to build a decentral messaging system for infected patients and their contacts. With blind signatures, we ensure that messages about infections are authentic and unchanged. A strong privacy focus enables data integrity, confidentiality, and privacy.

Note: In an earlier version we described Pepp-Pt as a decentralized system. This is no longer the case since researchers and organizations associated with DP-3T left the initiative.