Peer-to-peer COVID-19 contact tracing without the surveillance

Maciej Ceglowski asks for a massive surveillance program to defeat COVID-19.

However, as I mentioned on twitter — there IS an alternative, privacy-preserving approach, which is what is being done in Singapore with their TraceTogether app.

In summary, everyone carries a phone running an app which has an anonymized a random ID, scans local Bluetooth periodically for other people’s apps with their random IDs, and records them locally (not uploading to a server). If you find out you have COVID-19 you then trigger an upload of your contact history to a central server. That server then broadcasts out the list of IDs, and everyone you’ve been in contact with will then get a ping on their app to get tested, self-isolate, etc.

No central surveillance, no creepy big brother watching your location.

My pinboard has a few more write-ups on basically the same idea from various other places, including MIT. This is similar to what China’s app does, but (as far as I can tell) with more privacy.

It looks like the Singaporean government digital services team behind TraceTogether is putting together an open source version, at

IMO we have to do this or we will never get out of COVID-19 lockdown before 2021. I am massively in favour of adopting this approach in Ireland and across the world.

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  1. Posted March 26, 2020 at 11:27 | Permalink

    Hey Justin. We’ve been approached by a number of people in recent days about using tech to manage contact tracing. My initial question was one of privacy, and I’m impressed with how this was taken into account by the Singapore solution (which has yet to be open sourced, but will probably come in days). I think there’s other issues and am interested in your thoughts: The first one is really about effectiveness. In much the same way was herd immunity, this solution only works if everyone buys into it. Essentially, I’ve framed this as “how can we make an app that is as popular as WhatsApp, in a matter of days?”. The only apps that are ubiquitous are either shipped with a device, or have billion dollar companies behind them. I think it will be difficult to persuade everyone to download and use the app. Although, to be fair I think the government has done a marvellous job of getting the message out about Covid-19, so maybe they can help here. Usually, apps are popular because the provide instant gratification. “Insurance” apps never fall into this category, and I would expect that lots of people simply won’t bother downloading or running the app for this reason. Next there’s a question of battery life – Bluetooth scanning tends to be quite draining, so you’ve the added complication of running the app is bad for battery, which forms another disincentive to run it. Maybe, the Singapore solution has tried to minimise this, but there’s a trade off between accuracy (i.e.. always scanning versus sometimes scanning) and battery life. While iBeacons are quite efficient, this is the case on iOS only – On android, it means scanning like any other. (and vice versa if the answer was Eddystone). The thing I wonder about is the need for contact tracing after a time. If we follow the trajectory of Italy for example, it come to a stage where the hospitals are overrun, and contact tracing no longer matters.

  2. Emmett
    Posted March 27, 2020 at 12:04 | Permalink

    I found some info on the security of the technology found here :

    Worth a read maybe.

    Also , the idea that it may not help after a certain stage of the outbreak certainly applies in the case of Italy but for us in Ireland , with all the backlog of tests , if a number of these are positive and then we can trace their movements much more efficiently that our current procedures.

    The issue of “more people the better” using the app also applies but you would like to think the population would at the very least be able to download an app and keep their bluetooth on in the aid to help the health of the country.

    I personally think something like this needs to be implemented to assist sooner rather than later. Is there any way to check with Government is this something they are working on?