Illustration: Eniola Odetunde/Axios

Apple and Google announced a series of small changes to their coronavirus contact-tracing technology and shared additional technical details ahead of a launch in the coming weeks.

Why it matters: The system is likely to serve at the heart of major efforts around the world to use technology to detect potential coronavirus exposure, as it will be built into the two main smartphone operating systems.

What's new: Two weeks ago, the companies unveiled the system, which uses Bluetooth to determine if users have recently been in close proximity to someone with the coronavirus. Among the changes announced Friday:

  • The system will now share the strength of smartphone users' Bluetooth signals and allow public health authorities to set their own criteria for what constitutes a "contact."
  • The Bluetooth metadata will be encrypted to better protect against misuse of the technology to track individual users.
  • The protocol will share only rough time of shared contact, from a minimum of 5 minutes up to a maximum of 30 minutes, in 5 minute increments.
  • The numbers sent by each phone will now be randomly generated on a daily basis. In the initial proposal, each day's key was derived from another number that was tied to a particular device.
  • The companies are now dubbing the technology "exposure notification" to distinguish it from traditional contact tracing, in which health officials use patient data and interviews to build a record of people who may have been exposed to an illness.

Background: Under the Apple-Google technology, each participating user's phone will send out a random and frequently changing key to identify itself. If someone later reports they tested positive, their phone broadcasts out the keys it came in contact with, allowing those other users to be notified.

  • To protect privacy and limit the potential for abuse, no location data is used, individuals have to voluntarily participate and only health authorities are permitted to access the technology.
  • Google and Apple plan to release the technology in two phases. In the first phase, slated for mid-May, the two companies will build the technology into Android and iOS, but it will require a user to download an app. In the second step, the technology will be more deeply integrated into the operating system so people won't have to download a separate application to begin participating.

Go deeper: Why contact tracing is a key next step in slowing coronavirus' spread

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Illustration: Sarah Grillo/Axios

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