Asymmetric Information and App-Based Contact Tracing for Controlling COVID-19

The Collaboration Between Apple and Google

On April 10th Apple and Google did something unusual: they announced plans to work together. These two firms exert varying degrees of control over almost every operational smartphone on Earth—Apple through its production of both iPhones and the software that runs them, and Google thanks to a range of programs found in nearly all of the iPhone’s Android-powered rivals. As a result, the two companies have access to a planet-spanning network of sensors and computing power some 3.5bn devices strong. Their plan is to combine their assets to assist the tracking of the covid-19 pandemic.

Normally, collaboration between two such oligopolists would raise eyebrows to the roof. But these are not normal times. Tracing who is infected is essential to controlling the transmission of sars-cov-2, the virus causing the pandemic—and the ubiquity of mobile phones makes them plausible agents for doing so. The two firms’ networks will be joined together by a unifying update to their Bluetooth short-range wireless protocols. Bluetooth lets nearby devices communicate. The unification means it will be easier for others to build contact-tracing apps that work, without modification, on either platform.

America, Britain, Germany, Ireland and many other countries were already building apps to track infection. They will now rewrite their software to take advantage of this new arrangement. These apps will work by broadcasting, from each phone they are installed on, a string of numbers and letters unique to that handset. These broadcasts will be detectable by any other phone within Bluetooth range (about nine metres) that has the same app installed. An app will also, simultaneously, listen for strings that other phones are broadcasting. Each phone carrying such an app will record all the character strings it hears, and thus all the phones it has been close to. For reasons of security (and because Apple’s and Google’s underlying cryptographic protocols demand it), the string of characters a phone broadcasts will change every 15 minutes. Also, at least to start with, the records of strings received will be stored only on the receiving phone. That makes hacking or abusing the system hard.

If, however, a phone-user develops symptoms and then tests positive for covid-19, this arrangement changes. Different strings of characters—one for each day that the person in question was potentially infectious—are now broadcast by the authorities to every other app in the network. These strings, which Apple calls diagnosis keys, command all apps so contacted to search records collected since that person’s putative time of infection for signs of proximity to the infected individual’s phone.

What happens when a match is found is up to whoever deployed the app. A good response, though, would be to notify the person of interest, and ask him or her to get in touch and arrange to be tested. This way, infections will be detected quickly, and infected individuals offered suitable advice—and possibly quarantined. [The Economist, April 16, 2020]

1. Explain what market failure is app-based contact tracing hoping to solve?

2. What are the advantages and disadvantages of this solution?