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Mike McCready 2022-02-07 09:17:57 +01:00
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solution_architecture.md
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@ -38,7 +38,7 @@ To reduce the spread of [COVID-19](https://www.ecdc.europa.eu/en/covid-19-pandem
|:--:|
| **Figure 1: High-level architecture overview**|
The Corona-Warn-App (see [scoping document](scoping_document.md )), shown centrally in *Figure 1*, enables individuals to trace their personal exposure risk via their mobile phones. The Corona-Warn-App uses a new framework provided by Apple and Google called [Exposure Notification Framework](https://www.apple.com/covid19/contacttracing). The framework employs [Bluetooth Low Energy (BLE)](https://en.wikipedia.org/wiki/Bluetooth_Low_Energy) mechanics. BLE lets the individual mobile phones act as beacons meaning that they constantly broadcast a temporary identifier called Rolling Proximity Identifier (RPI) that is remembered and, at the same time, lets the mobile phone scan for identifiers of other mobile phones. This is shown on the right side of *Figure 1*.
The Corona-Warn-App (see [scoping document](scoping_document.md)), shown centrally in *Figure 1*, enables individuals to trace their personal exposure risk via their mobile phones. The Corona-Warn-App uses a new framework provided by Apple and Google called [Exposure Notification Framework](https://www.apple.com/covid19/contacttracing). The framework employs [Bluetooth Low Energy (BLE)](https://en.wikipedia.org/wiki/Bluetooth_Low_Energy) mechanics. BLE lets the individual mobile phones act as beacons meaning that they constantly broadcast a temporary identifier called Rolling Proximity Identifier (RPI) that is remembered and, at the same time, lets the mobile phone scan for identifiers of other mobile phones. This is shown on the right side of *Figure 1*.
Identifiers are ID numbers sent out by the mobile phones. To ensure privacy and to prevent the tracking of movement patterns of the app user, those broadcasted identifiers are only temporary and change constantly. New identifiers are derived from a Temporary Exposure Key (TEK) that is substituted at midnight (UTC) every day through means of cryptography. For a more detailed explanation, see *Figure 10*. Once a TEK is linked to a positive test result, it remains technically the same, but is then called a Diagnosis Key.
The collected identifiers from other users as well as the device's own keys, which can later be used to derive the identifiers, are stored locally on the phone in the secure storage of the framework provided by Apple and Google. The application cannot access this secure storage directly, but only through the interfaces the Exposure Notification Framework provides. To prevent misuse, some of these interfaces are subjected to [rate limiting](https://developer.apple.com/documentation/exposurenotification/enmanager/3586331-detectexposures). If app users are tested positive for SARS-CoV-2, they can update their status in the app by providing a verification of their test and select an option to send their recent keys from up to 14 days back. On the Corona-Warn-App back-end server, all keys of individuals that have tested positive are aggregated and are then made available to all mobile phones that have the app installed. Additionally, the configuration parameters for the framework are available for download, so that adjustments to the risk score calculation can be made, see the *Risk Scores* section.
@ -145,7 +145,7 @@ The Corona-Warn-App Server needs to fulfill the following tasks:
- Accept upload requests from clients
- Verify association with a positive test through the Verification Server and the associated workflow as explained in the “Retrieval of Lab Results and Verification Process” section and shown in the center of the left side of *Figure 7*.
- Accept uploaded diagnosis keys and store them (optional) together with the corresponding information (days since onset of symptoms/transmission risk level ) into the database. Note that the transport of connection metadata (e.g. IP) of the incoming connections for the upload of diagnosis keys is removed in a dedicated actor, labeled “Transport Metadata Removal” in *Figure 7*.
- Accept uploaded diagnosis keys and store them (optional) together with the corresponding information (days since onset of symptoms/transmission risk level) into the database. Note that the transport of connection metadata (e.g. IP) of the incoming connections for the upload of diagnosis keys is removed in a dedicated actor, labeled “Transport Metadata Removal” in *Figure 7*.
- Provide [configuration parameters](#data-format) to the mobile applications
- Threshold values for [attenuation buckets](#attenuation-buckets)
- Encoding and mapping of the Transmission Risk Level