computer science

TraceTogether

TraceTogether is a computer science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand TraceTogether rather than just read about it. In short: TraceTogether was a digital system implemented by the Government of Singapore to facilitate contact tracing efforts in response to the COVID-19 pandemic in Singapore. The main goal was a quick identification of persons who may have come into close contact with anyone who has tested positive for COVID-19.

Key takeaways

TraceTogether belongs to computer science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect TraceTogether to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of TraceTogether from memory before moving on to harder problems.

Reference excerpt

TraceTogether was a digital system implemented by the Government of Singapore to facilitate contact tracing efforts in response to the COVID-19 pandemic in Singapore. The main goal was a quick identification of persons who may have come into close contact with anyone who has tested positive for COVID-19. The system helps in identifying contacts such as strangers encountered in public one would not otherwise be able to identify or remember. Together with SafeEntry, it allows the identification of specific locations where a spread between close contacts may occur. Released on 20 March 2020, the system initially consisted only of an app by the same name. However, this was later supplemented by a physical token mainly intended for elderly and children who may not own a smartphone, or those who prefer not to use the app. The app was the first main COVID-19 tracking app released in the world and its development encouraged the development of similar apps in other countries. The app has raised significant concerns about the privacy of those who use the app, especially due to a lack of decentralised report processing and access to the data by police. However, the app states it has several features to ensure users' privacy, such as regularly rotating users' IDs and storing limited data. Despite the concerns over privacy, the app was slowly adopted by the population of the Singapore, eventually reaching a 92% adoption rate in May 2021. The app was now mandated for specific groups of people and those attempting to enter certain venues and events. On 9 February 2023, the system was deactivated after the authorities determined that the system was no longer required and closed down on 10 January 2024.

TraceTogether app

Technology

The app utilises a custom protocol, BlueTrace, which allows for a distributed approach whereby participating devices exchange proximity information whenever an app detects another device with the TraceTogether app installed. The protocol, and reference app implementations of it, were also open sourced as BlueTrace and OpenTrace respectively. Initial versions of the app required users to register using only their mobile number, since 7 April 2020, it requires users' NRIC or passport numbers, and added support for SafeEntry. The website states that the NRIC number was required in order to allow MOH to reach the right person when they need to give important health advice on COVID-19, and was stored in a secure server, never accessed unless needed for contact tracing, and never shared with other app users. The main goal of SafeEntry helps COVID-19 cases remember the places that they've visited. This helps MOH to identify potential infection clusters and perform cluster COVID-19 testing. Following installation, the user is requested to grant relevant permissions such as Bluetooth. Android users are additionally required to grant Location permission as Bluetooth can be used to derive location information when combined with beacons in fixed locations. To trace users the Ministry of Health (MOH) issues time sensitive anonymous temporary IDs that are used to identify the patient to all third parties. When two users of the app pass by, it uses the Bluetooth Relative Signal Strength Indicator (RSSI) readings between devices across time to approximate the proximity and duration of an encounter between two users. This proximity and duration information is stored on one's phone for 25 days on a rolling basis. Once a user tests positive for infection, the MOH works with them to map out their activity for past 14 days and requests the contact log. To facilitate the conduct of contact tracing measure to prevent further outbreak of any infectious disease, the user cannot withhold their contact information log under the Infectious Diseases Act (Chapter 137). The usage of the app had been limited by the technical limitations of needing to have the application to run in the foreground on iOS devices, and battery drain, but these problems had been reportedly addressed in the 2.1 version of the app released on 3 July 2020, and version 2.1.3 of 5 Aug added informational, work pass and SafeEntry QR features.

Release timeline The app was released on 20 March 2020, following 8 weeks of development by Singapore's Government Technology Agency in collaboration with Ministry of Health (MOH).

On 10 April 2020, following the lifting of the embargo on the Google-Apple Exposure Notification (GAEN) system, the developers announced that they had been working with Apple and Google on specifications which would allow for cross-border inter-operability, and had begun to incorporate these new APIs into TraceTogether. The developers envisaged this as a way to overcome the app's inability to access full background Bluetooth scanning functionality on iOS devices (which led to the app being active only when it ran in the foreground), and increase the pool of interoperable devices, both of which could have increased the contact tracing utility. On 5 June 2020, the Minister-in-charge of the Smart Nation Initiative Vivian Balakrishnan acknowledged in Parliament the inability of the TraceTogether app to work well particularly on iOS or Apple devices, and that these had not been overcome despite discussions at the technical and policy level with Apple. He subsequently explained that the Government had decided against using the Google-Apple Exposure Notification (GAEN) system, citing its inability to "identify how, when and whom the person was infected by or passed the infection to" and "the 'graph' not being available to the contact tracers". Instead, a new portable, wearable device, called the TraceTogether Token would be issued to all 5.7 million residents in order to increase the pool of participants. On 7 December 2020, market research firm Gartner crowned TraceTogether as the Asia-Pacific winner for its 2020 Government Eye on Innovation award, after the firm had conducted a poll among various government organisations around the world. With the discontinuation of the system, the app has been removed from all official mobile app stores.

… excerpt ends here. Continue reading the full article.

Illustrations

Worked examples

Example 1 — a first encounter with TraceTogether

Start with the simplest possible case. Write down what TraceTogether claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In computer science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to TraceTogether before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about TraceTogether ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of TraceTogether

In research: TraceTogether appears in computer science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses TraceTogether in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: TraceTogether is common in secondary-school and first-year university syllabi. It links to neighbouring topics 2020 establishments in Singapore, 2020 software, COVID-19 contact tracing apps, so understanding it makes those chapters shorter.
In everyday life: Look for TraceTogether outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study TraceTogether in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what TraceTogether means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain TraceTogether out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is TraceTogether in simple terms?

Why does TraceTogether matter?

Because it connects several computer science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study TraceTogether?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on TraceTogether.