Paper 2020/398

CAUDHT: Decentralized Contact Tracing Using a DHT and Blind Signatures

Samuel Brack, Leonie Reichert, and Björn Scheuermann


Contact tracing is a promising approach to combat the COVID-19 pandemic. Various systems have been proposed to automatise the process. Many 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.

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Publication info
Published elsewhere. LCN 2020
COVID-19Contact TracingPrivacy-enhancing technologiesDHTBlind Signatures
Contact author(s)
samuel brack @ informatik hu-berlin de
leonie reichert @ informatik hu-berlin de
2020-11-02: last of 3 revisions
2020-04-09: received
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      author = {Samuel Brack and Leonie Reichert and Björn Scheuermann},
      title = {CAUDHT: Decentralized Contact Tracing Using a DHT and Blind Signatures},
      howpublished = {Cryptology ePrint Archive, Paper 2020/398},
      year = {2020},
      note = {\url{}},
      url = {}
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