Review Article
Demystifying COVID-19 Digital Contact Tracing: A Survey on Frameworks and Mobile Apps
Table 1
Data storage in PEPP-PT subsystems.
| Subsystem | Data |
| Smartphone | Set of current and future ephemeral BLE IDs (EBIDs) to broadcast | Proximity history of the last 21 days (containing the observed EBIDs and timestamps) | OAuth2 [122] client secret for access to backend services (long term) | OAuth2 access token for access to backend services (short lived) |
| Backend | Persistent user ID (PUID) | OAuth2 client credentials of an app | OAuth2 temporary client access token (short term, 1 h) | Medium term (days to weeks): backend keys (), EBIDs, observed EBID lists | Push notification service ID (PID) |
| Not stored | Transaction Authentication Number (TAN): one-time password for uploading the observed EBID list to the backend |
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