Contrac: Did someone ever yield a match?

Hi have installed contrac on my X10ii from, has suggested in the comments in storeman. There is also a version available in chum, but installing this fails due to missing libprotobuf (as someone pointed out in the comments as well).
I know well about the drawbacks, especially the time needed for syncing contacts.
I’m still using the app and I’m trying to keep it in sync almost daily, though.
However, I’ve never yield any matches even though I have some 100k contacts and I was using the app quite from the start, first on my Gemini/XA2, now on the X10ii. My friends using the official corona-warn-app on iphone or android score matches almost daily currently.
Is contrac really working?


It’s excellent that you’re continuing to use the app, and it’s a really good question; I’d be interested to know too. The nature of the protocol is that the only the person who receives the alert knows that it happened.

The app has unit tests which check the alert status is working. I tested it against the test server back-end provided by SAP, as well as testing the Bluetooth advertisements against Android devices. So it’s had some pretty thorough testing. But ultimately the privacy-preserving nature of the protocol makes it hard to know for sure.


Thanks @Inte for rising this issue, I was wondering about that for quite some time.

I’ve been using Contrac for several month and haven’t got a matched key yet.
Last week I’ve attended an outdoor event after which plenty of other participants reported ‘red warnings’ on their German CoronaWarnApp. Contrac still shows no matched keys, though I have plenty of sent and received keys shown in Contrac.

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I used it during the second half of last year, but stopped to do so because there never was a match

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So we can assume it’s broken?

There are many factors involved. For example, following the specification, it will take more than one packet exchanged with someone who later registers positive, in order to trigger an alert. The level of sensitivity is controlled by configuration values downloaded from the server.

So I wouldn’t jump to the conclusion that it’s broken based just on this.

Have you got reports from users that they got alerts?

It makes me wonder, that plenty people around get warned with the ‘official’ abb but we don’t see any.

Any alerts in between, anyone?