Exposure Notification
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.

The Apple/Google protocol is similar to the Decentralized Privacy-Preserving Proximity Tracing (DP-3T) protocol created by the European DP-3T consortium and the Temporary Contact Number (TCN) protocol by Covid Watch, but is implemented at the operating system level, which allows for more efficient operation as a background process. Since May 2020, a variant of the DP-3T protocol is supported by the Exposure Notification Interface. Other protocols are constrained in how they operate as they have no special privilege over normal apps. This leads to issues, particularly on iOS devices where digital contact tracing apps running in the background experience significantly degraded performance. The joint approach is also designed to maintain interoperability between Android and iOS devices, which constitute the sheer majority of the market.

The ACLU stated the approach "appears to mitigate the worst privacy and centralization risks, but there is still room for improvement". In late April, Google and Apple shifted the emphasis of the naming of the system, describing it as an "exposure notification service", rather than "contact tracing" system.
Q312
Apple Inc.
ORG
Q95
Google
ORG
Q103470847
digital contact tracing
Concept
Q81068910
COVID-19 pandemic
Concept
Q1128437
contact tracing
Concept
Q94
Android
MISC
Q48493
iOS
MEDIA
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smartphone
Concept
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Bluetooth Low Energy
Concept
Q8789
cryptography
Concept
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COVID-19 app
Concept
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iOS 13.5
UNK
Q54809618
IOS 12.5
MISC
Q16920332
Google Play Services
MEDIA
Q19862344
Android Marshmallow
MISC
Q90697518
Decentralized Privacy-Preserving Proximity Tracing
MEDIA
Q93253333
Temporary Contact Number
UNK
Q97357752
Covid Watch
ORG
Q9135
operating system
Concept
Q205663
process
Concept
Q620615
apps
Concept
Q21637
ACLU
ORG
Q91018153
Exposure Notification
Concept
Q91018153
Exposure Notification
Concept
Q91018153
Exposure Notification
Concept
2020-04-10T00:00:00Z^^http://www.w3.org/2001/XMLSchema#dateTime
April 10, 2020
DATE
2020-05-20T00:00:00Z^^http://www.w3.org/2001/XMLSchema#dateTime
May 20, 2020
DATE
2020-12-14T00:00:00Z^^http://www.w3.org/2001/XMLSchema#dateTime
December 14, 2020
DATE
2020-05-01T00:00:00Z^^http://www.w3.org/2001/XMLSchema#dateTime
May 2020
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12.5
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NUMBER
-3^^http://www.w3.org/2001/XMLSchema#decimal
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developer
developer
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