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Privacy-Preserving Contact Tracing

Across the world, governments, and health authorities are working together to find solutions to the COVID‑19 pandemic, to protect people and get society back up and running. Software developers are contributing by crafting technical tools to help combat the virus and save lives.
In recent weeks, some concerns about certain tracking technologies have been raised by those who fear the curtailment of individual freedoms and their privacy.
At CrypTool, we try to explain as well as possible what is hidden in these decentralized tracing protocols so that you can form your own opinion on the subject.

Step 1

Alice’s phone broadcasts a random message every few minutes

In order to maintain user privacy, the message is sent over Bluetooth and does not use location for proximity detection.
This message is called a Proximity Identifier or EphID. Theses identifiers are unique and change often.

Try it yourself!

We have made a small animation, so that you can visualize each step of the protocol.
Alice
Bob
Charlie
David
Contagious
true
Alerted about infectivity
false
Notified by the app
false
Secret Initial Key
11jUIL8...
Secret Day Key
Past EphIDs (of the day)
Show
EphIDs heard
Show
Show server's data
Show
June 04, 2020
23:54
Protocol used
Simulation
Persons
Settings