Around two million people here have downloaded the national contact tracing app TraceTogether, after rules were introduced for foreign workers to do so as part of heightened measures to combat the spread of Covid-19 in dormitories and work sites.
The foreign workers have to meet tomorrow's app download deadline, as the country enters phase two of the reopening of the economy.
Latest figures show Singapore residents have also been downloading and updating their personal details in the app.
The number of users who have entered their identification numbers - a new requirement introduced earlier this month - has gone up to 790,000, the Smart Nation and Digital Government Group told The Straits Times.
Privacy advocates have argued against the collection of identity numbers such as NRIC or foreign identification numbers (FINs), saying that a centralised database provides an attractive target for hackers.
A Ministry of Health (MOH) spokesman said the capturing of identity numbers in the updated TraceTogether app allows for a higher degree of identity assurance, which is necessary for the issuing of official quarantine orders, for instance.
Although TraceTogether users would have provided their mobile-phone numbers, people could change their phone numbers or switch off their phones, making it harder for contact tracers to get in touch with the close contacts of Covid-19 patients.
With NRIC data, contact tracers can cross-check NRIC or FIN data against the Government's central administrative database to locate individuals.
"Being able to contact them in a timely manner is critical, to ensure they take precautions to isolate themselves if necessary, to keep their families and friends safe," the MOH spokesman added.
Identity numbers are also needed for TraceTogether and digital check-in system SafeEntry - installed at over 110,000 locations including malls, supermarkets and workplaces - to work jointly to manage the spread of Covid-19.
For instance, not all visitors to a place where a Covid-19 patient had been during the infectious period - from data provided by SafeEntry - are subject to the same risk of infection.
Another layer of checks is required: examining these visitors' exposure duration to and how far they were physically from the Covid-19 patient.
TraceTogether can estimate the approximate distance between users and the duration of their encounters based on the Bluetooth signal strength between devices.
Only someone who has been within 2m of a Covid-19 patient for 30 minutes is required to be put under quarantine.
Other forms of contact with confirmed Covid-19 cases in the same place for very short periods of time - for example, if they were just passing by each other - are likely to be "transient in nature", said the MOH spokesman.
These transient contacts will then be asked to monitor their own health for 14 days from the date of their visits to the places where Covid-19 patients had been.
The Straits Times understands that digital tools such as TraceTogether and SafeEntry are effective in tracking foreign workers only in specific scenarios - such as when they travel across their work sites and dormitories. These tools are not as effective when they mingle with the larger population in Singapore, the majority of whom have not downloaded TraceTogether.
For contact tracing apps like TraceTogether to be effective, at least three-quarters of the population here, or 4.2 million people, need to be users.
This is why the Government is rolling out a wearable token that works in similar ways to the app, to increase the adoption rate.
The first batch of 300,000 TraceTogether Tokens is being produced and will be issued later this month.