Medical staff walk to the National Centre for Infectious Diseases building at Tan Tock Seng Hospital in Singapore on January 31, 2020. Roslan Rahman | APF | Getty Images

Less than a week after launching an app to track potential exposure to the coronavirus, Singapore is making the technology freely available to developers worldwide. The city-state rolled out an app called TraceTogether on March 20 and described it as a supplementary tool for its contact tracing efforts that relied on the recall and memory of infected individuals. Contact tracing is the process of identifying those with close contact with infected patients.

How the app works

Phones that have the app installed exchange short-distance Bluetooth signals when their users are near one another. Records of those encounters, including the duration, are stored in their respective phones for 21 days, according to the app's frequently asked questions section. It added that location data is not collected. If a user is diagnosed with COVID-19, the respiratory illness caused by the coronavirus, they could allow Singapore's health ministry to access their app data to identify people who had close contact with the infected individual. To be clear, Singapore says that when a person is contacted, they are required by law to assist the health ministry in accurately mapping out their movements and interactions to minimize the risk of widespread infection. That includes providing location timelines and physical or digital logs that may be collected by apps.

Privacy concerns

To allay privacy concerns around what is essentially an instance of high-tech surveillance by the state, Singapore's health ministry said personal details such as a user's name is not collected by the TraceTogether app. It does not record location data or access the user's phone contact list. Data logs are stored on phones in encrypted form; information on potential close contacts is stored not by their phone numbers but by using "cryptographically generated temporary IDs," the health ministry said. Still, the logs can be decrypted and analyzed by Singapore's health ministry when it is deemed necessary and the users can be easily identified from that information. More broadly, privacy concerns are growing as governments around the world rely on technology to track people in their efforts to combat the coronavirus pandemic. South Korea is publishing the movements of people before they were diagnosed with the virus by retracing their steps using GPS phone tracking, credit card records, surveillance video and personal interviews with patients, the Washington Post reported earlier this month. Israel has an app that can warn users if they've crossed paths with someone infected by the coronavirus.

Response to Singapore's app had been "largely positive," according to a representative of the Smart Nation and Digital Government Office at the Prime Minister's Office of Singapore. "More than 500,000 users with a Singapore-registered mobile number downloaded the TraceTogether app within the first 24 hours of its launch," the spokesperson told CNBC. On Monday, Singapore foreign minister Vivian Balakrishnan, who is also the minister-in-charge of the country's smart nation initiative, said in a Facebook post that the app had been installed by more than 620,000 people so far. The health ministry did not immediately respond to CNBC's request for comment on how many close contacts have been identified so far using the app.

Open-source

The Smart Nation and Digital Government Office spokesperson said other countries have expressed interest in adopting the technology behind the app. "Our engineering team is working around the clock to prepare the codebase for open source adoption," the spokesperson said. The app is built on a combination of centralized and decentralized models of contact tracing; the developers call the technology the BlueTrace protocol. TraceTogether was created by a team of 40 engineers over a period of eight weeks. Responding to a query from CNBC about other potential uses of the technology, the spokesperson said: "At present, BlueTrace, the technology underlying TraceTogether, is used to complement existing contact tracing methods and support nationwide efforts to combat COVID-19. There are no plans to extend the use of TraceTogether for non-contact tracing purposes." The coronavirus, which was first reported in China's Hubei province last December, has spread rapidly worldwide. It has infected at least 416,600 people and killed more than 18,500, according to the latest numbers from the World Health Organization. Cases and fatalities in Europe and the United States have spiked in recent weeks. Singapore reported 631 cases as of March 25 noon local time, including two deaths and 160 patients discharged. The city-state had been praised globally for its approach in managing the outbreak through stringent contact tracing and quarantine efforts, but cases in the country have also surged in recent days.

Watch: Economic impact of coronavirus outbreak will last 'at least a year'