Contact tracing is a proven tool in containing outbreaks of infectious diseases. Contact tracing has been credited with helping flatten the curve in countries such as South Korea, when combined with other measures.
One study suggests that if contact tracers successfully detected 90% of symptomatic cases and reached 90% of their contacts it could reduce transmissions by more than 45%. But, over recent weeks, a split has emerged between two different types of contact tracing apps—centralised and decentralised versions.
Both types use Bluetooth signals to determine how close someone has come to a diagnosed covid-19 patient. The app then sends alerts to other users who may have been infected. So fundamentally, both apps can gather information that is then used to alert people whether they pose a risk of spreading the disease.
The main difference between centralised and decentralised contact tracing apps relates to how contact matching is done. Under a centralised model, the anonymised data is uploaded to a remote server where matches are made with other contacts.
That contrasts with the decentralised model which gives users more control over their information by keeping it on the phone. As a result, matches with people who may have contracted the virus are made on the phone.
Google, Apple, and Germany’s health ministry are just a few of the organisations that are promoting decentralised contract tracing apps. They say that this approach offers users a higher degree of privacy and security.
On the other hand, the supporters of the centralised model, which includes the UK, South Korea and Singapore, insist that their model gives authorities more insight into the spread of the contagion as well as how the app is performing.
Unsurprisingly, both apps have not been without problems. It turns out Singapore’s TraceTogether (centralised), which was widely viewed as one to emulate, was only being used by 20% of the local population. Part of the problem is that the app does not work properly when in the background on iPhone because of the way Apple restricts use of Bluetooth. Australia’s CovidSafe app (also centralised) reported similar issues.
The blockchain model
In principle, decentralised contact tracing apps work almost in a similar fashion as blockchain-based applications or decentralised apps (dapps). Similar to Facebook or Google digital identities, the app provides digital records of coronavirus exposure, which is securely maintained using blockchain technology.
The benefits of this approach are two-fold. First, the distributed nature of the technology allows for increased transparency regarding data usage. Since no central authority is controlling all the information, users can access the ledger and enhance control of their data. As a result, authorities will not be able to use personal information without user consent.
This enhanced transparency will also result in more accurate reporting and a more efficient response against the spread of the virus.
The second point relates to data security and privacy. Blockchain is incredibly secure, and many industries already trust it to handle sensitive information. The technology is tamper-resistant and also prevents fraud and forgery.
Integrating blockchain in contact tracing applications ensures the privacy and anonymity of data since it limits the ability of either authorities or a hacker to use the computer server logs to track specific individuals and identify their social interactions.
U.S based NetObjex launched its blockchain-based app last month to enable people who test positive for COVID-19 antibodies to get a clearance to return to work. The app directs users to blood test collection centres in their areas for an antibody test, and the lab results are then reported straight to the app. It will also add QR codes that users can scan in order to check the level of antibodies in their bodies.
Although built specifically for antibodies test, the app can also be used for contact-tracing purposes. However, tracking will only be effective if there are enough downloads and user engagement.
A number of countries, mainly in Europe, are deploying decentralised contact tracing apps, though a majority are flocking to the API-based system developed by Apple and Google. It would be interesting to see whether African countries are willing to jump on the bandwagon or develop their own customised blockchain-based solutions.