A coalition of the willing

Developing a contact tracing app that keeps personal data private

Illustration of people in a public place with their cellphones emitting Bluetooth chirps

Smartphones with the PACT app use Bluetooth signals or "chirps" to determine distance between nearby cell phones. Anyone using the PACT app can notify other individuals of COVID-19 exposure without revealing any private information to other people, the government, healthcare or cell service providers.

The ability to conduct aggressive contact tracing of those infected with the coronavirus will be fundamental in protecting vulnerable populations as the nation takes steps to reopen and Americans begin returning to their daily lives, according to CDC Director Robert Redfield.

For centuries, contact tracing has happened manually with public health officials going door-to-door, tracking down people who came in contact with the infected patient, and then repeating the process with the new known contacts, until the transmission chain is halted. It relies on a patient’s memory, who they’ve been in contact with, where they’ve been and when. It misses those people unknown to the patient – the people who sat near them in the movie theater or at a restaurant, for example.

Today’s technology might be the solution for a speedier and more thorough contact tracing protocol. One effort, using a smartphone app, called “PACT,” short for Private Automated Contact Tracing, shows promise and gotten the attention of Apple and Google. PACT is led by the Massachusetts Institute of Technology, Lincoln Laboratory and Massachusetts General Hospital with many partners including cryptographers, physicians, health care providers, privacy experts, scientists and engineers around the world. Among the PACT close collaborators is BBN Technologies, a part of Raytheon Intelligence & Space, which is one of the four businesses that form Raytheon Technologies.

“From the beginning, this has really been a coalition of the willing,” said Kim Gavin, BBN Technologies intelligence programs director. “Our company and many of the others in the PACT coalition are funding technology efforts through internal research and development to enhance contact tracing in pandemic response. So it’s just been pretty awesome to see all these people come together during a crisis; really contribute together technically, scientifically, academically to put forth energies to help slow the COVID-19 pandemic”

The PACT app uses encrypted Bluetooth data to ensure personally identifiable information remains anonymous and secure. Bluetooth emits pings called “chirps,” and phones running the app collect and record these chirps from nearby phones also running the app. If a person tests positive for COVID-19, they can upload their chirps for the past few weeks and others with the app would then be notified when and how long they’d been exposed to an infected individual. Since COVID-19 patients are infectious even before symptom onset or if they’re asymptomatic, it makes it even more important that those who are exposed to the virus are identified and isolated.

“Unlike some of the contact tracing apps developed in other countries, this is completely anonymous – the app doesn’t know who you are, who you’ve interacted with and where you’ve been,” said Daniel ”Gigs” Gregory, BBN Technologies PACT principal investigator. “In the United States, we value our privacy, and that’s one area where we’re lending our expertise.”

BBN Technologies is experimenting with what is called zero-knowledge Succinct Non-interactive Arguments of Knowledge, or SNARKs, as part of keeping personally identifiable information secure. SNARKs are used in cryptography, much like public keys are used for encrypted emails, to verify the authenticity of the information.

“It allows you to publish information that can be proven to have originated from an authorized source without having to know that it’s authorized or who authorized it, keeping it private,” Gregory said.

The company has also lent its knowledge of machine learning to create simulations on how the spread of the coronavirus would be impacted by the aggressiveness of the contact tracing.

“Our models suggest that a contact tracing app can help slow the spread of the virus but only if enough people use them,” Gregory said. “Once the app is released, it will be up to the states on how it’s used.”

The BBN team is also fine-tuning the accuracy of measuring the distance between the Bluetooth devices as it may vary from two to five meters.

“We’re looking at different ways to collect the data or augment the Bluetooth standard so that we can get better measurement results,” Gregory said. “We’re experimenting with advanced algorithms that use triangulation signals to help improve the distance accuracy. We’ll be running more tests to see what works the best, and then push those results to Apple and Google to show them what we’re doing and how implementing different protocols and standards work.”

While the “coalition of the willing” looks like a who’s who in academia, technology and healthcare, including several MIT institutions, Apple, Google, CDC, Army Research Lab, Air Force Research Lab, Sandia National Laboratory, Carnegie Mellon University, Boston University, Northeastern University, Global Health Partners and Mass General Hospital, among others, BBN Technologies became a PACT partner from the outset, and they're making important contributions, according to Gavin.

“We’re hoping that the work that we’ve done with DARPA, IARPA and other government agencies on other projects can be brought to bear on this problem,” Gavin said. “We can bring our innovation and lessons learned to address this unique and critical problem whether it’s our expertise in cybersecurity; cryptography and privacy concerns; mobile technology; artificial intelligence and machine learning, there’s a number of areas where we can apply the research and development we’ve done in the past toward this PACT effort.”

Published On: 06/15/2020