Apple's latest updates to its operating systems add another security feature to the Find My service, so you have an even better chance of finding your lost iPhone, iPad or Mac if it ever happens. As long as you've enabled this option, you can leverage other Apple users' devices to find yours on the map.
Why would it even be necessary if your lost Apple device is still connected to the Internet via a Wi-Fi network or cellular data? It would not. But if your missing iPhone, iPad or MacBook were away from any hotspots and in a non-service area, Apple's anonymous audience improvement could be the key to geolocating the device. It's a great companion to "Send Last Place", which transfers your device's last location to Apple's servers before the battery dies and stores it for 24 hours.
The feature in question, Offline Finding, uses your lost device's low-power Bluetooth connection to talk to other Apple devices nearby with Bluetooth enabled. And best of all, the whole process works with final encryption.
With E2E encryption, no one can abuse the system. Hackers will not be able to capture and decode your device's location, intercepting marketers will not be able to track you in their stores, and even Apple will not see any of the data being sent or received. It is completely anonymous.
How Offline Finding Works
Offline Finding uses a background process called "Search Party" to send and receive Bluetooth beacons at regular intervals, and it can even do its job when the device is in sleep state. And it does this with limited battery power for all affected devices, so you should see little or no difference in power consumption.
Your device has been assigned a volatile public encryption key, so it changes frequently over time. It does so because a static identifier can allow others to lock it for tracking purposes. But as it is constantly changing, there is no way to abuse it.
When the lost smartphone, tablet or computer has no Internet connection, it will transfer its public encryption key to another nearby Apple device via Bluetooth. The other device then uploads its own encrypted location information, along with the hash of your lost device's public key, to Apple's servers to help you identify it later. When you then use Find My iPhone, Find My iPad or Find My Mac service, you will send the encrypted location information, and your device will decrypt it.
But that's where the catch comes in. To take advantage of Offline Finding, you must have at least two Apple devices using the same iCloud account with two-factor authentication. That's because all your connected devices use the same private key and set of rotating public keys.
When you use Find My on your device that is not missing, it uploads public key hashes to Apple's servers. Apple then automatically searches for its encrypted location servers for a matching identifier. When the cryptographic identifier is found, Apple sends it back to your device where your private key decrypts it.
Apple has not specified exactly how often public keys rotate or how they keep track of their hashes. Since your missing device's public key hash has probably changed since the last time location information for it was uploaded, it does not match the current ID of your missing Apple device. So they are likely to store and keep a brief history of past public keys to find matches in these cases.
How to verify Offline Finding Is On
By default, if you had Find My iPhone, iPad or Mac on before updating to iOS 13, iPadOS 13 or macOS 10.15 Catalina, Offline Finding should already be on. If only one of the devices had the Find My service enabled but not another device, it may not have been activated automatically. Check the following to make sure it is on.
On either iOS 13 for iPhone or iPadOS 13, open the Settings app and tap your name upwards to see your Apple ID settings. Then click "Find My" and then "Find My iPhone." On the next page, make sure "Enable Offline Finding" is enabled.
Open "System Preferences" and then press "Apple ID" to see your account information. Then select "iCloud" from the sidebar and make sure "Find My Mac" is enabled under the list of apps. If you need to turn it on, check it and then press "Allow" when prompted. When Find My Mac is enabled, press "Options" next to it and then make sure "Enable Offline Finding" is enabled.
It's not a perfect solution
Let's say you left your MacBook in a public library or someone snagged your open laptop as you walked to the bathroom of a cafe. If open, it can connect to a hotspot to send location data. But if it was closed, which would probably be the case, it could still send its public key to other devices with Bluetooth. A thief won't have much time to open your Mac and disconnect Wi-Fi and Bluetooth, so you'll have a good chance of finding it if you're fast.
However, if your iPhone was stolen, the thief could turn it off or enable airplane mode, which would not only disable Wi-Fi and mobile connections but also Bluetooth. In these cases, neither sending last place nor online search would be of great use. And now that Offline Finding exists, it is more likely that thieves will make sure Bluetooth is disabled along with the other connections.
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