A smartphone app developed by the Singaporean digital government team will be open sourced. The app allows the tracking of citizens’ encounters with the carriers of COVID-19.
The government alongside the developers of the app, named TraceTogether, have urged citizens to use the app so that in the event of an encounter with a COVID-19 carrier, which will then allow easy tracing of other people who may have also been exposed to the virus.
Health authorities can then be better-informed as to who is in need of quarantine as well as prioritise their resources to those who require help the most.
The app does not track users via space and it is opt-in. Rather, it conducts recording of encountered individuals. To allow for this, location services and Bluetooth must be switched on when another phone with the app running enters into range. Once this happens, there are exchanges of four nuggets of information, which are (1) a temporary identifier or device nickname, (2) the phone’s model, (3) Bluetooth signal strength and (4) a timestamp. The app merely computes distances between users and does not track them. Thus, location services are needed.
The BlueTrace Manifesto was announced on Facebook by Singapore’s foreign affairs minister, Vivian Balakrishnan, in order to promote the work done to make the app.
The app and what it enables has been explained by the development team at Singapore’s Government Technology Agency.
Jason Bay, who is the Senior Director of Government Digital Services at the country’s national digital transformation agency, GovTech, explained: “While GPS works well in wide, open spaces, it fares poorly when it comes to indoor and highly urbanised settings…If you are one floor down in a building, your GPS location could look the same as someone in the floor above you because of signal reflections and multipath propagation effects.”
Given that Bluetooth was the only choice left, Mr Bay added that “because it is a low power signal that degrades very quickly over distance, we can use signal strength to figure out the distance between two phones within a reasonable margin of error.”
However, the team discovered that not all Bluetooth have been created equal: “In the course of developing this app, we found out that the Bluetooth signal strength difference between two phones can be 1,000 percent or even more—up to 10,000 percent even…To use a metaphor, some people speak with booming voices and others have very soft voices. If you are trying to estimate the distance based on volume, you will have to calibrate the microphone you use for each speaker – loud or soft. One of the hardest parts of this project was characterising and calibrating across different models of phones,” Mr Bay remarked.
Accordingly, GovTech partnered with researchers at Singapore’s Nanyang Polytechnic and the Institute for Infocomm Research, who made possible accurate signal-testing by using anechoic chambers (rooms that block out radio signals).
From this, the app was successfully built by the GovTech team with less privacy-invading Bluetooth, as opposed to the eyes-in-the-sky GPS.
With the app, viral logic is utilised to defeat the virus itself: “After all, you could argue that the virus doesn’t care where transmission happens; it’s only interested in whether there is a hospitable host in close contact,” Mr Bay noted.
Singapore is currently striving to disseminate its code to the rest of the world.
The BlueTrace Manifesto read: “We are working around the clock to finalise our protocol reference documents and reference implementation, to open source what we have built, so that others may deploy their own flavours of TraceTogether – each implementing the BlueTrace protocol…We appreciate your patience in the meantime.”
