When a patient is tested positive for Covid-19 authorities need to track recent contact the patient made to warn or quarantine those contacts. CoFight-19 is a volunteering effort to create a complete (basic) stack for setting up a system for tracing contacts.
Each user registers the device phone number and gets back a unique user ID.
Using only Bluetooth, CoFight identifies nearby phones that have the app installed. It records the IDs that come in close proximity and a timestamp.
When there's a confirmed case, the patient can upload all the data to a central server. Authorities then can then notify the known contacts, thus stopping the spread of the virus.
Each device registers a BLE server and client. We define a Service UUID and a Characteristic UUID. We advertise the Service UUID and devices are scanning for that UUID. When a device is found, they connect and read the characteristic that contains the user ID.
On iOS there is a limitation from Apple: iOS devices can't advertise their Service UUID when in the background so it's recommended to keep the app in the foreground (eg. when the user is expected to be in a crowded space) and enable the in-app battery save mode.
Everything is stored on device's keychain for security reasons. Data older than 21 days are removed on app initialization.
The app is avaible in English and Greek. If you need to support another language, just add the localisation, copy the English localisation and then translate it.
- BLE can record up to 10 meters. But closed contact for the virus spread is considered up to 4 meters.
