Covid Watch

Last updated
Covid Watch [1]
Covid Watch Logo Brandmark Blue.png
FormationFebruary 19, 2020 (2020-02-19) [2]
FounderTina White [3]
Founded atStanford, CA
HeadquartersTucson, AZ
Products COVID-19 app solution using GAEN or TCN Protocols
Services Exposure Alerts
Executive Director
Tina White
James Petrie
Rhys Fenwick
Zsombor Szabo
200+ active

Covid Watch was an open source nonprofit founded in February 2020 with the mission of building mobile technology to fight the COVID-19 pandemic while defending digital privacy. [4] The Covid Watch founders became concerned about emerging, mass surveillance-enabling digital contact tracing technology and started the project to help preserve civil liberties during the pandemic. [5] [6] [7]

Covid Watch [8] began as an independent research collaboration between students at Stanford University and the University of Waterloo, and it was the first team in the world to publish a white paper, [9] develop, [10] [11] and open source [12] a fully anonymous Bluetooth exposure alert protocol - the CEN Protocol, later renamed the TCN Protocol - in collaboration with CoEpi in early March 2020. [13] This was followed by the rapid development of very similar decentralized protocols in early April 2020 like DP-3T, PACT, [14] and Google/Apple Exposure Notification.

The Covid Watch team had over 200 active volunteers from around the world including advisers in public health, epidemiology, privacy, policy, and law from universities like Stanford, Waterloo, UW, UCSF, and Berkeley. [4] [15]

Covid Watch also built a fully open source mobile app for sending anonymous exposure alerts first using their own TCN Protocol in April 2020 [16] and later using the nearly identical protocol within the Google/Apple exposure notification (GAEN) framework when the GAEN APIs were released in May 2020. [17] [18] Also in May 2020, Covid Watch launched the first calibration and beta testing pilot of the GAEN APIs in the United States at the University of Arizona. [19] [20]

In August 2020, the app launched publicly for a phased roll-out in the state of Arizona. [21] [22] [23] Covid Watch volunteers and staff also collaborated with the University of Arizona on research to improve the estimation of infection risk from anonymous Bluetooth data to better inform private quarantine recommendations. [24]

At the end of 2020, the Covid Watch nonprofit closed, but the Covid Watch app and related open source technologies continue to be implemented for public health departments by the WeHealth organization. [25]


As the pandemic began its outbreak in North America, on February 19, 2020, Stanford University PhD candidate and DOE CSGF Fellow Tina White made a public Effective Altruism (EA) forum post about researching smartphone technology like GPS to alert people privately of COVID-19 exposure. [26] This post got the attention of James Petrie at University of Waterloo who had started writing an academic paper on Overleaf on February 7, 2020, exploring private, decentralized methods using MAC addresses. [27] The two researchers began the research collaboration between Stanford and Waterloo, which formed into the nonprofit Covid Watch.

Anonymous, decentralized Bluetooth exposure alerts first publicly appeared on March 2, 2020, when CW's James Petrie posted a PDF describing the privacy model in CW public slack channels, shared with researchers and collaborators worldwide. [28] Covid Watch's description of the technology and procedure for anonymous exposure alerts was shared widely on social media [29] and on the original Covid Watch blog written by Rhys Fenwick. [30] On March 10, 2020, Tina White reached out to Apple engineers to describe BLE anonymous contact tracing technology and background issues on iOS.

A description of the CEN Protocol: the first anonymous, decentralized Bluetooth exposure notification protocol to be published online in Covid Watch's whitepaper on 20 March 2020 and open sourced on the Covid Watch GitHub 17 March 2020. CEN Protocol.png
A description of the CEN Protocol: the first anonymous, decentralized Bluetooth exposure notification protocol to be published online in Covid Watch's whitepaper on 20 March 2020 and open sourced on the Covid Watch GitHub 17 March 2020.

Covid Watch developer Zsombor Szabo built the first open source, decentralized, anonymous exposure alert protocol called the CEN Protocol. [31] [32] [33] On March 12, 2020, Zsombor Szabo pushed his first commit to GitHub, [34] laying the foundations of the CW app, completing a proof of concept on March 17 and sharing the video of the working technology on YouTube. [35] Finally, on March 20, 2020, the CW team published a White Paper describing the CEN / TCN protocol. [36] [37]  

Tina White presented the technology at Stanford HAI's COVID-19 and AI virtual conference on April 1. [38] [39] [40] After that, Covid Watch began receiving significant news coverage. [41] Covid Watch then helped other groups like the TCN Coalition and MIT SafePaths [42] implement the TCN Protocol within their open source projects to further the development of decentralized technology and foster global interoperability of contact tracing and exposure alerting apps, a key aspect of achieving widespread adoption. [43]

In early April, three other teams publish decentralized, anonymous Bluetooth protocols. On April 3, 2020, the first DP^3T white paper commit [44] is published along with its first commit on GitHub. [44] On April 6, Henry de Valence of the Zcash Foundation publishes a comparison of CEN/TCN with the new white paper proposal from DP^3T. [45] On April 9, 2020, the MIT PACT protocol spec [46] authored by Rob Rivest, Ramesh Raskar, Vanessa Teague, and many more cited CW and DP^3T and Nicky Case published a comic describing how the CW and DP^3T Protocols work. [47] Finally, after CW and CoEpi published their reference implementation CEN (TCN) protocol [48] and along with several other teams communicated to Apple the issues they faced regarding a successful exposure notification app, Apple and Google announced their contact tracing API [49] on April 10, 2020.  

On April 28, 2020, CW implemented the TCN protocol in a fully functional anonymous exposure alert app with Android bridging, first available in Apple TestFlight via the Stanford App Store. [50] In May 2020, Covid Watch launched the first calibration and beta testing pilot of the GAEN protocol in the United States at the University of Arizona. [19] [20]

Related Research Articles

Contact tracing Finding and identifying people in contact with someone with an infectious disease

In public health, contact tracing is the process of identifying persons who may have come into contact with an infected person ("contacts") and subsequent collection of further information about these contacts. By tracing the contacts of infected individuals, testing them for infection, isolating or treating the infected, and tracing their contacts, public health aims to reduce infections in the population. Diseases for which contact tracing is commonly performed include tuberculosis, vaccine-preventable infections like measles, sexually transmitted infections, blood-borne infections, Ebola, some serious bacterial infections, and novel virus infections. The goals of contact tracing are:

COVID-19 apps Mobile apps designed to aid contact tracing

COVID-19 apps are mobile software applications for digital contact tracing during the COVID-19 pandemic, i.e. the process of identifying persons ("contacts") who may have been in contact with an infected individual.

Pan-European Privacy-Preserving Proximity Tracing (PEPP-PT/PEPP) is a full-stack open protocol designed to facilitate digital contact tracing of infected participants. The protocol was developed in the context of the ongoing COVID-19 pandemic. The protocol, like the competing Decentralized Privacy-Preserving Proximity Tracing (DP-3T) protocol, makes use of Bluetooth LE to discover and locally log clients near a user. However, unlike DP-3T, it uses a centralized reporting server to process contact logs and individually notify clients of potential contact with an infected patient. It has been argued that this approaches compromises privacy, but has the benefit of human-in-the-loop checks and health authority verification. While users are not expected to register with their real name, the back-end server processes pseudonymous personal data that would eventually be capable of being reidentified. It has also been put forward that the distinction between centralized/decentralized systems is mostly technical and PEPP-PT is equally able to preserve privacy.


BlueTrace is an open-source application protocol that facilitates digital contact tracing of users to stem the spread of the COVID-19 pandemic. Initially developed by the Singaporean Government, BlueTrace powers the contact tracing for the TraceTogether app. Australia, New Zealand, and the United Arab Emirates have already adopted the protocol in their gov apps, and other countries were considering BlueTrace for adoption. A principle of the protocol is the preservation of privacy and health authority co-operation.

TraceTogether is a digital system the Government of Singapore implemented to facilitate contact tracing efforts in response to the COVID-19 pandemic in Singapore. The main goal is 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.

The (Google/Apple) Exposure Notification (GAEN) system, originally known as the Privacy-Preserving Contact Tracing Project, is a framework and protocol specification developed by Apple Inc. and Google to facilitate digital contact tracing during the COVID-19 pandemic. When used by health authorities, it augments more traditional contact tracing techniques by automatically logging encounters with other notification system users using their Android or iOS smartphone. Exposure Notification is a decentralized reporting based protocol built on a combination of Bluetooth Low Energy technology and privacy-preserving cryptography. It is used as an opt-in feature within COVID-19 apps developed and published by authorized health authorities. Originally unveiled on April 10, 2020, it was first made available on iOS on May 20, 2020 as part of the iOS 13.5 update and on December 14, 2020 as part of the IOS 12.5 update for older iPhones. On Android, it was added to devices via a Google Play Services update, supporting all versions since Android Marshmallow.

COVIDSafe Contact tracing applications commissioned by the Australian Department of Health

COVIDSafe is a digital contact tracing app announced by the Australian Government on 14 April 2020 to help combat the ongoing COVID-19 pandemic. The app is based on the BlueTrace protocol, originally developed by the Singaporean Government, and was first released on 26 April 2020. The app is intended to augment traditional contact tracing by automatically tracking encounters between users and later allowing a state or territory health authority to warn a user they have come within 1.5 metres with an infected person for 15 minutes or more.

TCN Protocol Proximity contact tracing protocol

The Temporary Contact Numbers Protocol, or TCN Protocol, is an open source, decentralized, anonymous exposure alert protocol developed by Covid Watch in response to the COVID-19 pandemic. The Covid Watch team, started as an independent research collaboration between Stanford University and the University of Waterloo was the first in the world to publish a white paper, develop, and open source fully anonymous Bluetooth exposure alert technology in collaboration with CoEpi after writing a blog post on the topic in early March.

Digital contact tracing Method of contact tracing using mobile devices

Digital contact tracing is a method of contact tracing relying on tracking systems, most often based on mobile devices, to determine contact between an infected patient and a user. It came to public prominence in the form of COVID-19 apps during the COVID-19 pandemic. Since the initial outbreak, many groups have developed nonstandard protocols designed to allow for wide-scale digital contact tracing, most notably BlueTrace and Exposure Notification.

Decentralized Privacy-Preserving Proximity Tracing Proximity contact tracing protocol

Decentralized Privacy-Preserving Proximity Tracing is an open protocol developed in response to the COVID-19 pandemic to facilitate digital contact tracing of infected participants. The protocol, like competing protocol Pan-European Privacy-Preserving Proximity Tracing (PEPP-PT), uses Bluetooth Low Energy to track and log encounters with other users. The protocols differ in their reporting mechanism, with PEPP-PT requiring clients to upload contact logs to a central reporting server, whereas with DP-3T, the central reporting server never has access to contact logs nor is it responsible for processing and informing clients of contact. Because contact logs are never transmitted to third parties, it has major privacy benefits over the PEPP-PT approach; however, this comes at the cost of requiring more computing power on the client side to process infection reports.

NHS COVID-19 UK contact tracing app for COVID-19

NHS COVID-19 is a voluntary contact tracing app for monitoring the spread of the COVID-19 pandemic in England and Wales. It has been available since 24 September 2020 for Android and iOS smartphones, and can be used by anyone aged 16 or over.

On April 16, 2020, Nodle released The Whisper Tracing Protocol white paper and the Coalition App on Android. The protocol is intended to be a privacy first Digital contact tracing tool developed for the 2020 COVID-19 pandemic. The project has been spun off into The Coalition Foundation. The protocol is being used for the Government of Senegal's Daancovid19 mobile contact tracing app initiative. Daancovid19 is the Senegalese digital response against the coronavirus. It was started by a handful of digital professionals and subsequently brought together nearly 500 volunteer experts from the private, public, and civil society. The respective Coalition App has been promoted by the City of Berkeley, California to their residents.

NZ COVID Tracer Mobile software application

NZ COVID Tracer is a mobile software application that enables a person to record places they have visited, in order to facilitate tracing who may have been in contact with a person infected with the COVID-19 virus. The app allows users to scan official QR codes at the premises of businesses and other organisations they visit, to create a digital diary. It was launched by New Zealand's Ministry of Health on 20 May 2020, during the ongoing COVID-19 pandemic. It can be downloaded from the App Store and Google Play.

Carmela Troncoso Spanish telecommunication engineer

Carmela González Troncoso is a Spanish telecommunication engineer and researcher specialized in privacy issues, and a LGBT+ activist. She is currently a tenure track assistant professor at École Polytechnique Fédérale de Lausanne (EPFL) in Switzerland and the head of the SPRING lab. Troncoso gained recognition for her leadership of the European team developing the DP-3T protocol that aims at the creation of an application to facilitate the tracing of COVID-19 infected persons without compromising on the privacy of citizens. Currently she is also member of the Swiss National COVID-19 Science Task Force in the expert group on Digital Epidemiology. In 2020, she was listed among Fortune magazine's 40 Under 40.

COVID Alert Canadian contact-tracing app for COVID-19

COVID Alert is the Exposure Notification service app for the country of Canada. It launched in the province of Ontario on July 31, 2020, and became available in nearly all Canadian provinces by October of that year, excluding Alberta, and British Columbia.

SwissCovid is a COVID-19 contact tracing app used for digital contact tracing in Switzerland. Use of the app is voluntary and based on a decentralized approach using Bluetooth Low Energy and Decentralized Privacy-Preserving Proximity Tracing (dp3t).

COVID Tracker Ireland Contact tracing application released by the Government of Ireland on 7 July 2020

COVID Tracker Ireland is a digital contact tracing app released by the Irish Government and the Health Service Executive on 7 July 2020 to prevent the spread of COVID-19 in Ireland. The app uses ENS and Bluetooth technology to determine whether a user have been a close contact of someone for more than 15 minutes who tested positive for COVID-19. On 8 July, the app reached one million registered users within 36 hours after its launch, representing more than 30% of the population of Ireland and over a quarter of all smartphone users in the country. As of August 2021, over 3,030,000 people have downloaded the app.

Public health mitigation of COVID-19 Measures to halt the spread of the respiratory disease among populations

Speed and scale are key to mitigation of COVID-19, due to the fat-tailed nature of pandemic risk and the exponential growth of COVID-19 infections. For mitigation to be effective, (a) chains of transmission must be broken as quickly as possible through screening and containment, (b) health care must be available to provide for the needs of those infected, and (c) contingencies must be in place to allow for effective rollout of (a) and (b). or Stay Safe is a digital contact tracing app launched by the Philippine government as a response to the COVID-19 pandemic in the Philippines. The mobile app was developed and published by MultiSys Technologies Corporation.


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