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Freshfields TQ

Technology quotient - the ability of an individual, team or organization to harness the power of technology

| 5 minutes read

Contact tracing apps in China, Hong Kong, Singapore, Japan, and South Korea

This post is part of a series on contact tracing apps. You can read our introduction to the series and get links to the other entries here.


China has seen the largest-scale adoption of COVID-19 tracking apps in the world. A QR code system designed to show the user’s health status was first adopted in Hangzhou in February 2020 hosted on the Alipay app. This system was developed at the request of the State Council. Local governments across China have since developed their own versions of the app though each may have different criteria and algorithms depending on the local situation. Each local app may be hosted on different platforms. By mid-April, Alibaba was hosting apps for more than 200 cities and Tencent had over 300, with still more hosted on Baidu.

The apps generally work by assigning a colour code (green, yellow or red) using an algorithmic assessment of the user’s travel history and health status. Green codes grant unrestricted movement, while yellow and red codes require the user to be quarantined for seven (yellow) or 14 days (red). Police and security guards at checkpoints throughout Chinese cities have been checking users’ QR codes for several months now. Some cities are only granting access to metro stations to persons with a green code, with the same restrictions on buying train tickets or using a taxi, for example.

It has been noted that the apps for different cities and provinces are not mutually compatible. For example, a user from Hubei with a green code from the Hubei app may be rejected to from public transportation in Shanghai if they do not have a green code from the local app. There is now a push from the central government to adopt a unified system.

The technology companies hosting the apps have claimed that the software for the apps were developed by local governments and that they have no knowledge of the algorithms that generate the health codes. The government has declined to explain how it works, but has acknowledged that law enforcement authorities were involved in the development.

Hong Kong

Since 19 March 2020, all arrivals to Hong Kong from overseas have been required to undergo a mandatory 14-day quarantine at home or at a designated hotels. The Hong Kong government operates a mobile app that uses geofencing technology to ensure that the person subject to quarantine has not left the designated quarantine location.

Upon arrival, each person is given a wristband with a unique QR code and is required to download the tracking app and pair with the wristband with the app by scanning the QR code. Once the user arrives at the quarantine location, they calibrate the app by walking the perimeter of quarantine location. The app may at any time request the user to re-scan the QR code on the wristband to confirm that the user is at the same location as their mobile device.

According to the Hong Kong government, the tracking app was designed in consultation with the Hong Kong Privacy Commissioner for Personal Data to ensure compliance with data protection regulation. The app does not use GPS location tracking and does not track or record the user’s exact geographic location. Instead, using geofencing technology, which detects surrounding communication signals such as Wifi, Bluetooth and GPS, it tracks the user’s location relative only to the calibrated perimeter.


On 20 March 2020, the Singaporean government launched a contact tracing app, TraceTogether, which claims to be the first national Bluetooth contact tracing solution. The app’s protocol, BlueTrace has been made publicly available. The app works by logging Bluetooth encounters between users who have the app activated – the devices exchange non-personally identifiable messages that are stored locally on each device. If a user is infected or is the subject of contact tracing, they will be asked to share their encounter history with the health authority. Only the health authority is able to decrypt the encounter history.

For a solution such as TraceTogether to be effective will requires a high adoption rate. To date, the app has been downloaded by around a fifth of Singapore’s population. Additionally a Bluetooth the signal can be detected at distances of up to two metres or through walls and requires careful calibration to be used as an accurate proxy for contact. iOS devices moreover cannot scan or be scanned by non-iOS devices while the app is in the background (i.e. not actively open), and will only work effectively if the user has the app open constantly.

Although BlueTrace was designed with privacy considerations in mind (PDF), Singapore’s Prime Minister Lee Hsien-loong acknowledged in a national address that “there will be some privacy concerns” with using the contact tracing app that need to be weighed against the benefits of being able to end Singapore’s current quarantine arrangements.


On 14 March 2020, the Japanese government announced that it has developed a contact tracing app which will be launched and become available on app stores at the end of April. The app works by using Bluetooth. If users who agree to download and activate the apps encounters each other, their devices will exchange and record encrypted information. If a user is infected, the app will alert other users who have encountered that user within the past two weeks that they have encountered an infected user.

For privacy reasons, whether to download or activate the app is completely voluntary, and the alert sent to users will not contain the name of the infected user, the location, date or time of contact with the infected user. The alert message will be something like: “there is a possibility that you have come into close contact with an infected person within the last week.”. The aim of the app is to suggest that users to check their health condition by themselves first and, if they have any concerns, suggest reaching out to a public health centre.

South Korea

The Ministry of the Interior and Safety has developed an app in March 2020 for quarantined individuals to contact case workers and to keep track of their location using GPS. The app is not mandatory for individuals subject to a quarantine order, as the current system of monitoring through telephone calls is to continue, meaning that individuals who are unable to use the app or have privacy concerns can opt-out of using it.

Using government data, a number of third-party apps and websites provide users with near real-time updates. Corona 100m (Co100), launched in February 2020, is Korea’s most popular mobile app related to COVID-19. It alerts users when they come within 100 metres of a location that has been visited by an infected person.

South Korea also plans to build out a “smart city” database operated by the Korea Center for Disease Control and Prevention (KCDC) that will give real-time data feeds on patients, including their location, time spent at specific locations, CCTV footage and credit card transactions. The aim is to cut the time needed to trace a patient’s movements from around one day to 10 minutes. The system will compile data uploaded by the KCDC along with data from the National Police Agency, the Credit Finance Association of Korea, three telecommunications companies and 22 credit card companies. The government has stated that investigators will need to obtain police approval to access the database and it will be restricted to a small number of authorised users.

With many thanks to Sunghee Chae of Lee & Ko for the analysis regarding South Korea.

Other posts in this series:


asia, covid-19, intellectual property, data, data protection