Demystifying COVID-19 Digital Contact Tracing: A Survey on Frameworks and Mobile Apps

Table 2

Main characteristics of contact tracing frameworks.

Framework	Approach	Source code	Health authority	Location data collected	Self-reporting
DP-3T	Decentralised	Open [7]	Yes	No	No
Google/Apple	Decentralised	Proprietary^1	Yes	No	No
PEPP-PT NTK	Centralised	Open^2	Yes	No	No
ROBERT	Centralised	Open [80]	Yes	No	No
BlueTrace	Centralised	Open [123]	Yes	No	No
TraceSecure	Centralised^3	Not available	Yes	No	No
DESIRE	Hybrid^4	Not available	Yes	No	No
PACT (UW)	Decentralised	Open [124]	Yes	No	No
PACT (MIT)	Decentralised	Not available	Yes	Optional	No
TCN	Decentralised	Open [125]	Optional	No	Yes
OpenCovidTrace	Decentralised	Open [126]	Yes	Yes^5	No
Whisper Tracing	Decentralised	Not available	No	Optional	Yes

¹Proprietary API; open source reference implementations are provided for a server [127] and an Android app [128]. ²The goal of the consortium is to open source the code, but the repositories are not available yet [129]; open-source reference implementation is provided for an Android app [130, 131]. ³While the approach is based on TraceTogether, it adds additional mechanisms (e.g., homomorphic encryption) to improve privacy aspects. ⁴It integrates some of the advantages of centralised and decentralised approaches. While users do not need to register as in the case of BlueTrace, the backend server still is able to match infected and requesting users based on PET and the risk score computation. ⁵When the Google/Apple protocol is used.