The codes are 16 byte (ie 128 bit) numbers that are cryptographically derived from your daily tracing key. Of course all use of Bluetooth will reveal your MAC a

The codes are 16 byte (ie 128 bit) numbers that are cryptographically derived from your daily tracing key. Of course all use of Bluetooth will reveal your MAC address, but this privacy concern already existed and is why many devices now rotate a randomly generated MAC address periodically. (https://covid19-static.cdn-apple.com/applications/covid19/current/static/contact-tracing/pdf/ExposureNotification-BluetoothSpecificationv1.1.pdf https://covid19-static.cdn-apple.com/applications/covid19/cu...)