Centralized or Decentralized? The Contact Tracing Dilemma

The COVID-19 pandemic created a noticeable challenge to the cryptographic community with the development of contact tracing applications. The media reported a dispute between designers proposing a centralized or a decentralized solution (namely, the PEPP-PT and the DP3T projects). Perhaps, the time constraints to develop and deploy efficient solutions led to non-optimal (in terms of privacy) solutions. Moreover, arguments have been severely biased and the scientific debate did not really happen until recently. In this paper, we show the vulnerabilities and the advantages of both solutions systematically. We believe that none offers any sufficient level of privacy protection and the decision to use one or another is as hard as using automated contact tracing at the first place. A third way could be explored. We list here a few possible directions.