google/exposure-notifications-internals

An issue was discovered in the GAEN (aka Google/Apple Exposure Notifications) protocol through 2020-10-05, as used in COVID-19 applications on Android and iOS. The encrypted metadata block with a TX value lacks a checksum, allowing bitflipping to amplify a contamination attack. This can cause metadata deanonymization and risk-score inflation. NOTE: the vendor's position is "We do not believe that TX power authentication would be a useful defense against relay attacks.

The Rolling Proximity Identifier used in the Apple/Google Exposure Notification API beta through 2020-05-29 enables attackers to circumvent Bluetooth Smart Privacy because there is a secondary temporary UID. An attacker with access to Beacon or IoT networks can seamlessly track individual device movement via a Bluetooth LE discovery mechanism.