Fig 1.
COVID-19 new cases (3. August. 2020).
The number of COVID-19 new cases over countries (the early detected countries: China, South Korea, Sweden, and Italy; the most highly infected countries: Iran, Spain, France, United States, United Kingdom, and Brazil).
Fig 2.
Quarantine workflow of South Korea.
Table 1.
Description of Gowalla dataset.
Table 2.
Encryption and decryption time of IPE.
Fig 3.
Privacy-preserving contact tracing workflow.
Fig 4.
Example of contact tracing with functional encryption techniques.
The location IDs are decomposed into digits and separately encrypted. The time values are transformed into ordinal numbers and then encrypted. When a set of confirmed IDs is given, the algorithm finds possible contacts by checking the location match and time overlap (within the given threshold 60 min) compared with those of the confirmed cases.
Fig 5.
(A) Infection graph; Infected patients and their contacts are depicted as a graph. (B) PPCT executor; The progress of privacy-preserving contact tracing is displayed where a bar represents a piece of CPU core. The progress bars of each core are on the right side. (C) Tracing result table; The infection probability of a person is represented as a wave in a circle.
Fig 6.
Query processing time varying the number of infected people and time threshold.
Fig 7.
Query processing time varying the number of multi-cores.