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clarify transmission of TAN

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Thomas Klingbeil 2020-06-08 13:03:04 +02:00
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solution_architecture.md
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@ -70,7 +70,8 @@ The flow for using the app is as follows, referencing the steps from *Figure 2*:
- **Step 2:** The samples are transported to the lab together with a “Probenbegleitschein” which has a machine-readable QR code on it as well as other barcodes (lab ID, sample IDs).
- **Step 3:** As soon as the test result is available meaning the samples have been processed, the software running locally in the lab (lab client) transmits the test result to the Laboratory Information System together with the GUID from the QR code. The Laboratory Information System hashes the GUID and posts it together with the test result to the Test Result Server through a REST interface (*Figure 3*, step A), which in turn makes it available to the verification server.
- **Step 4a:** After signing up for notifications in step 1, the user’s mobile phone regularly checks the Verification Server for available test results (polling, figure 3, steps 5-8). This way, no external push servers need to be used. If results are available, the user is informed that information is available. The result themselves as well as recommendations for further actions are only displayed after the user has opened the app (see the scoping document for more details).
- If the test returns a positive result, users are asked to upload their keys to allow others to find out that they were exposed. If the users agree, the app retrieves a short-lived token (TAN) from the Verification Server (see also *Figure 3*, steps 9-13). As the Verification Server does not persist the test result, it is fetched from the Test Result Server once more (*Figure 3*, steps 10-11). The TAN is uploaded together with the diagnosis keys of the last 14 days to the Corona-Warn-App Server (*Figure 3*, step 14).
- If the test returns a positive result, users are asked to upload their keys to allow others to find out that they were exposed. If the users agree, the app retrieves a short-lived token (TAN) from the Verification Server (see also *Figure 3*, steps 9-13). As the Verification Server does not persist the test result, it is fetched from the Test Result Server once more (*Figure 3*, steps 10-11).
The TAN is used as authorization in the HTTP header of the POST request for upload of the diagnosis keys of the last 14 days to the Corona-Warn-App Server (*Figure 3*, step 14).
- The Corona-Warn-App Server uses the TAN to verify the authenticity (*Figure 3*, steps 15-17) of the submission with the Verification Server.
- The TAN is consumed by the Verification Server and becomes invalid (*Figure 3*, step 16).
- If the Corona-Warn-App Server receives a positive confirmation, the uploaded diagnosis keys are stored in the database (*Figure 3*, step 18).
@ -79,7 +80,7 @@ The flow for using the app is as follows, referencing the steps from *Figure 2*:
![Figure 3: Data flow for the verification process](images/solution_architecture/figure_3.svg "Figure 3: Data flow for the verification process")
Note regarding *Figure 3* and *Figure 4*: The white boxes with rounded corners represent data storage. The HTTP method POST is used instead of GET for added security, so data (e.g. the registration token or the TAN) can be transferred in the body.
Note regarding *Figure 3* and *Figure 4*: The white boxes with rounded corners represent data storage. The HTTP method POST is used instead of GET for added security, so data (e.g. the registration token) can be transferred in the body.
As mentioned before, users might have decided against retrieving test results electronically, or the lab may not support the electronic process. Step 3 of *Figure 2* shows that in these cases the health authority (“Gesundheitsamt”) reaches out to the patient directly. Also during this conversation, the teleTAN can be provided to the patient, which can be used to authorize the upload of diagnosis keys from the app to the Corona-Warn-App Server (step 4b of *Figure 2*). This process is also visualized in *Figure 4*. Whenever patients are contacted regarding a positive test result, they can choose to receive a teleTAN. The teleTan is retrieved from the web interface (*Figure 4*, step 1) of the portal service by a public health officer. This service in turn is requesting it from the Verification Server (2-3). The teleTAN is then issued to the officer (4-5) who transfers it to the patient (6). Once the patient has entered the teleTAN into the app (7), it uses the teleTAN to retrieve a registration token from the Verification Server (8-10). Once the user has confirmed the upload of the Diagnosis Keys, the application requests a TAN from the server, using the registration token (11-13). This TAN is needed by the server to ensure that the device is allowed to do the upload. These TANs are not visible to the user. After uploading the TAN and the diagnosis keys to the Corona-Warn-App Server (14), the Corona-Warn-App Server can verify the authenticity of the TAN with the Verification Server (15-16) and upon receiving a confirmation, store the diagnosis keys in the database (17).