Details on Apple-Google Digital Contact Tracing System using Bluetooth technology

On Friday, Apple and Google announced they will work together on a digital contact tracing system that would use Bluetooth technology to alert users when they’ve been in contact with someone infected with COVID-19.  In essence, the companies are creating a digital contact tracing system powered by a network of smartphones to better help the public understand when they may have been exposed to the virus. The system will enable both iPhones and Android devices to anonymously broadcast signals to other nearby devices using Bluetooth and scan for beacons from other phones in proximity. The two mobile phone operating system competitors  are releasing APIs supporting Bluetooth and cryptography on smartphones running the iOS and Android systems.  The goal is to help governments and health agencies reduce the spread of the coronavirus. According to a joint statement, user privacy and security are “central to the design.”

Through this technology, Apple and Google aim to implement a system that would enable your smartphone to notify you if you’ve recently been in contact with a potentially contagious coronavirus person, while trying to avoid compromising user privacy.  The system is opt-in only, meaning users must give their explicit consent and choose to participate in the program.  Both companies say the system was designed with privacy in mind.

Contact tracing—tracking who has a disease and who they’ve been near in order to limit the spread of an outbreak—is a crucial tool in fighting diseases, including covid-19. But it’s traditionally a very human job that involves talking to people, detailing their movements, and making a lot of phone calls. Now the question is whether technology can do the job even faster, and without violating people’s privacy, security, and liberty.  Will the Applie-Google contact tracking system work?

  • Apple earlier partnered with the U.S. government on an app to help people recognize Covid-19 symptoms and find help if needed.
  • Google has been active providing its location data to help governments track the effectiveness of confinement measures.

Many countries are now looking to develop contact tracing apps to help stem the spread of the coronavirus. A Bluetooth low energy protocol (BLE) is often used to broadcast the person’s status and alert others to contact. The two largest developers of smart phone and tablet software said they would be launching a “comprehensive solution” that includes APIs and operating system-level technology to assist in enabling contact tracing.

In May, both companies will release APIs that enable interoperability between Android and iOS devices using apps from public health authorities. These official apps will be available for users to download via their respective app stores.

In the coming months, Apple and Google will work to enable a broader Bluetooth-based contact tracing platform by building this functionality into the underlying platforms. This is a more robust solution than an API and would allow more individuals to participate, if they choose to opt in, as well as enable interaction with a broader ecosystem of apps and government health authorities.  To encourage transparency and privacy in the apps, the companies pledged to to publish information about the work and work with interested stakeholders on developing the technology.


As part of this partnership, Google and Apple are releasing initial draft technical documentation including Bluetooth and cryptography specifications and framework documentation.

For a closer look about what you need to know about Apple and Google’s contact tracing system, please read this Business Insider article.

The Verge attempts to answer the 12 biggest questions related to the Apple-Google joint contact tracing system in this post.


Image Credit: Bryce Durbin/TechCrunch



Q&A: Apple and Google discuss their coronavirus tracing efforts


5 thoughts on “Details on Apple-Google Digital Contact Tracing System using Bluetooth technology

  1. The basic idea is that as jurisdictions flatten the curve of infection and begin to consider re-opening parts of society, they need to implement a comprehensive “test and trace” scheme. You want to test people widely and thoroughly for the disease, as this article by Umair Irfan from Monday explains. And then, as you discover new cases, you want to see who those people may have come in contact with during the time that they were infectious.

    Historically, this has been a manual process. Since the COVID-19 outbreak began, some countries have turned to technological means in an effort to enable public health authorities to find more people who may have been exposed and do so more efficiently. So far, it’s not clear that tech-enabled contact tracing has been all that effective. The system relies on voluntary participation, which has generally been weak. And the Bluetooth technology on which the system depends carries with it a high potential for false positives: it’s just not powerful enough to distinguish between cases where people were in very close proximity from ones in which they were 15 or more feet away.
    The biggest concern most people have expressed about the collaboration is that it will lead to damaging privacy violations. Democratic senators have led the charge here, sending an open letter to the companies expressing their fears. I’m less worried. For one thing, Apple and Google’s system is cleverly designed to maximize individual privacy; it avoids capturing location data and instead records only the proximity of your smartphone to someone else’s. And for another, I value my own privacy less during a public health emergency. I trust Apple and Google to prevent my personal health information from being identified as mine and shared with others, but given the design of the system, I fail to see how a breach would be catastrophic even if it did somehow materialize.

    The second set of concerns has to do with how the system will work in practice. Apple and Google answered a lot of questions about that subject today; here are what I took to be the most consequential.

    First, the companies said that by phase two of their effort, when contact tracing is enabled at the level of the operating system, they will notify people who have opted in to their potential exposure to COVID-19 even if they have not downloaded the relevant app from their public health authority. My understanding is that the operating system itself will alert people that they may have been exposed and direct them to download the relevant public health app. This is significant because it can be hard to get people to install software; Singapore saw only 12 percent adoption of its national contact-tracing app. Putting notifications at the system level represents a major step forward for this effort, even if still requires people to opt in.

    Second, Google said it would distribute the operating system update through Google Play services, a part of Android controlled by the company that allows it to reach the majority of active devices. (Google says it will be available to everyone running Android 6.0, also known as Marshmallow, and higher on devices that have the Google Play store.) This is highly preferable than relying on carriers, which have historically been slow to distribute updates. It remains to be seen exactly which devices will be eligible for the update, on Android as well as on iOS. But it seems likely that the companies will be able to reach most active devices in the world — a significant feat. (Related: someone asked the companies what percentage of the population we need to use the system to get it to work. No one knows.)

    Third, the companies said they would prevent abuse of the system by routing alerts through public health agencies. (They are also helping those agencies, such as Britain’s National Health Service, build apps to do just that.) While the details are still being worked out, and may vary from agency to agency, Apple and Google said they recognized the importance of not allowing people to trigger alerts based on unverified claims of a COVID-19 infection. Instead, they said, people who are diagnosed will be given a one-time code by the public health agency, which the newly diagnosed will have to enter to trigger the alert.

    Fourth, the companies promised to use the system only for contact tracing, and to dismantle the network when it becomes appropriate. Some readers have asked me whether the system might be put to other uses, such as targeted advertising, or whether non-governmental organizations might be given access to it. Today Apple and Google explicitly said no.

    Fifth, I’ve heard conflicting claims about the ability of Bluetooth-based tracking to measure distances. Last week I told you that Bluetooth could not distinguish between phones that were within six feet of one another, in contradiction of advice from public health agencies, and those that might be 20 or even 30 feet away. One reader pointed me to a part of the Bluetooth standard known as received signal strength indication, or RSSI, that is meant to offer fine-grained location detail.

    So, to wrap up: do we feel more or less optimistic today about tech-enabled contact tracing than we did before?

    I still think that digital contact tracing is unlikely to be one of the two or three most important aspects of a country’s coronavirus response plan. Experts have told me that social distancing, wide-scale testing, and isolating sick individuals are significantly more important. And when it comes to contact tracing, we know that human beings often do a better job than smartphones — and some have argued that we need to hire hundreds of thousands of them to do the job.

    At the same time, it’s possible to see how digital contact tracing could at least complement other, related efforts, including manual contact tracing. Compared to what, say Hong Kong is doing to test and trace, distributing digital tracking bracelets to everyone getting off the plane at the airport, what Apple and Google have proposed can only be described as a half measure. But in the United States at least, it may be the case that a series of half measures are all we will have to rely on.

  2. Normally I do not read articles on tech blogs, but this write-up of the Apple-Google contract tracing system was an exception! Your writing style is amazing. Thanks, for a comprehensive and very well documented article.

  3. Great article on Apple-Google contact tracing system. It’s unusual to see cooperation between these tech giants.

    Each public health authority in each country or region must first agree to adopt Apple and Google’s Exposure Notification API. Next, the health authority must create an iOS and Android app for their region dedicated to supporting Exposure Notifications.

    In the United States, rather than creating a single contact tracing app, the decision to support Exposure Notifications is made by each state’s public health authority. Alabama, South Carolina, and North Dakota are among the first U.S. states to express interest in Apple and Google’s Exposure Notifications API for assisting COVID-19 contact tracing.

    Support for Washington, Minnesota, Maryland, Washington D.C., Connecticut, and California was added for iPhone and Android on November 30, 2020.

    Which U.S. states are using Apple’s Exposure Notification API?
    States Status
    Alabama Available (Apple/Google)
    Alaska Not Available
    Arizona Available (Apple/Google)
    Arkansas Not Available
    California Pilot Rollout (Apple/Google)
    Colorado Available (Apple/Google)
    Connecticut Available (Apple/Google)
    Delaware Available (Apple/Google)
    Florida Not Available
    Georgia Not Available
    Hawaii Not Available
    Idaho Not Available
    Illinois Not Available
    Indiana Not Available
    Iowa Not Available
    Kansas Not Available
    Kentucky Not Available
    Louisiana Not Available
    Maine Not Available
    Maryland Available (Apple/Google)
    Massachusetts Not Available
    Michigan Available (Apple/Google)
    Minnesota Available (Apple/Google)
    Mississippi Not Available
    Missouri Not Available
    Montana Not Available
    Nebraska Not Available
    Nevada Available (Apple/Google)
    New Hampshire Not Available
    New Jersey Available (Apple/Google)
    New Mexico Not Available
    New York Available (Apple/Google)
    North Carolina Available (Apple/Google)
    North Dakota Available (Apple/Google)
    Ohio Not Available
    Oklahoma Not Available
    Oregon EN Express app in development
    Pennsylvania Available (Apple/Google)
    Rhode Island Not Available
    South Carolina Will Participate
    South Dakota Not Available
    Tennessee Not Available
    Texas Not Available
    Utah Not Available
    Vermont Not Available
    Virginia Available (Apple/Google)
    Washington Available (Apple/Google)
    West Virginia Not Available
    Wisconsin Not Available
    Wyoming Available (Apple/Google)
    District of Columbia Available (Apple/Google)

    *Some states and territories may not opt-in to supporting a contact tracing app that uses Apple and Google’s exposure notification API.

    Best wishes and good health to everyone!

  4. This kind of collaborative work by Google and Apple pleases me very much. Thanks for the update.

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