MIT develops privacy-preserving system for anonymous contact tracing of COVID-19 patients

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Published: April 10, 2020 7:02:27 PM

The proposed system, called Private Automatic Contact Tracing (PACT), uses the Bluetooth technology, relying on its short-range signals emitted from smartphones.

Covid-19, Research, Massachusetts Institute of Technology, MIT, Lincoln Laboratory, Electrical Engineering & Computer Science, Apps, Disease, Public health, Pandemic, Cyber security, Technology and society, Media Lab, coronavirus tracking apps, coronavirus contact tracing technology, coronavirus innovationWith their system, the team is essentially asking a phone to send out this kind of random signal all the time and to keep a log of these signals. (Image: MIT/Christine Daniloff)

COVID-19: To effectively tackle the COVID-19 pandemic, it is essential that authorities track down all the people who have come in contact with a patient who has tested positive. So far, the only way to do that is the authorities asking the patient to list out all the people he has come in contact with, which leaves numerous strangers out of the loop. To tackle this problem, a team of researchers from Massachusetts Institute of Technology (MIT), along with experts from other institutions, is developing a system to augment the tracing of manual contact by public health officials, MIT said in a statement.

Coronavirus Outbreak: How does the MIT system work?

The proposed system, called Private Automatic Contact Tracing (PACT), uses the Bluetooth technology, relying on its short-range signals emitted from smartphones. The statement said that these signals represented a string of numbers, similar to ‘chirps’, which are ‘heard’ by nearby smartphones and stored in their memory.

A person who has tested positive can upload the list of Bluetooth signals or chirps that their phone sent out within the last 14 days into a database, which can be scanned by other users to check if any signal caught by their phones matches those in the database. In case of a match of signals, the individual will be notified about the potential exposure to the virus.

Explaining the basic principle of the system, Principal Investigator of the project and MIT Professor Ron Rivest said in the statement that essentially, one party has to keep track of what they have broadcast, while the other has to track what they have heard.

The conception

Bluetooth is already used by smartphones to inform other devices of their presence. An example of this technology is used in Apple’s ‘Find My’ feature, which allows a user to trace their iPhone or MacBook from other devices via these Bluetooth chirps.

Co-Principal Investigator and MIT Lincoln Laboratory’s Cyber Security and Information Science Division Associate Head Marc Zissman said that in the ‘Find My’ system, the lost phone sends a broadcasting signal made of random numbers, like someone lost in the middle of the ocean and waving a light. This system inspired them to develop this technology for COVID-19 pandemic.

COVID-19: What about the privacy of the parties?

Lately, with security breach happening on so many different platforms, users have become skittish while using such tracking apps. However, the MIT statement said that the system they are devising will keep the identities of both the parties anonymous.

This is also a development based on Apple’s technology. Professor Zissman explained in the statement that in the ‘Find My’ feature, if another Apple user passes the bluetooth zone of the lost phone, the other phone does not know any details about the lost phone, it just catches the signal and informs Apple that a lost phone’s signal was caught.

Similarly, for this project, Professor Rivest said in the statement that they are using cryptographic techniques which will generate random and rotating numbers which are not just anonymous, but are actually pseudonymous. They constantly change their ‘ID’, he said, and they cannot be used to reach the individual whose phone transmitted the signal.

The aim is to not attach a private email ID or a phone number to the tracking account, which is what countries like India and South Korea are doing with the apps they developed to trace the possible movement of COVID-19 via GPS.

How can phone owners use the system?

The system developed by MIT is basically asking phones to emit these ‘chirps’ all the time and maintain a list of signals sent out. Simultaneously, it is also asking the phone to detect the chirps it hears and log those which would be significant for medical purposes. The significance of chirps is based on certain factors like the distance between the two phones and the duration over which the signals were transmitted.

With their system, the team is essentially asking a phone to send out this kind of random signal all the time and to keep a log of these signals. At the same time, the phone detects chirps it has picked up from other phones, and only logs chirps that would be medically significant for contact tracing — those emitted from within an approximate 6-foot radius and picked up for a certain duration of time, say 10 minutes.

Phone owners would get involved by downloading an app that enables this system. After a positive diagnosis, a person would receive a QR code from a health official. By scanning the code through that app, that person can upload their log to the cloud. Anyone with the app could then initiate their phones to scan these logs. A notification, if there’s a match, could tell a user how long they were near an infected person and the approximate distance.

Impact on public health

The development process for the PACT system has been done with the consultancy of medical experts to ensure that it would benefit the authorities in tracing contacts. The research team is being led by infectious disease expert and Harvard Medical School Associate Professor Louise Ivers, who said in the statement that an automated approach could greatly impact the medical community’s ability to control the pandemic in the US as well as in other countries. She further said that the good thing about the technology was that it could be flexible to meet the needs of health authorities in managing the contacts of exposed individuals. It could notify someone to go into self-isolation or request them to connect with specialists via the app regarding their well-being and daily symptoms. It could also notify an individual to get tested if they saw a cluster of cases.

The app would help in not just flattening the curve of the outbreak, the statement read, but also to aid in a safe transformation to the public life once lockdowns and curfews are lifted.

What next?

The prototyping of the system is being done by engineers at the Lincoln Laboratory and one of the biggest challenges before the team was to develop a mechanism for an Android device to pick up chirps from an iPhone and vice versa. Last week, a test showed that they had overcome the challenge and had achieved this capability.

The next step towards the implementation of this system is to rope in smartphone manufacturers as well as developers of software, like Apple, Google and Microsoft, by proving to them that the prototype is feasible for them to use. The team is also demonstrating the prototype to state as well as federal government agencies in the US for further implementation.

Not just wanting the system to be limited in its outreach, the team is working with several other teams in the US as well as Europe for the development of similar contact-tracing systems which also ensure the privacy of users.

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