Apple's latest updates to its operating systems add another security feature to the Find My Phone service, giving you the chance to find your lost iPhone, iPad, or Mac if it ever happens. As long as you have the option enabled, you can use the devices of other Apple users to find yours on the map.
Why would that be necessary if your lost Apple device is still connected to the Internet over a Wi-Fi network? or mobile data? It would not. However, if your missing iPhone, iPad, or MacBook were not near hotspots and in a non-service area, Apple's anonymous crowd-sourcing enhancement could be the key to geolocating your device. It's a great addition to "Send Last Location," where your device's last location is sent to Apple's server before the battery is empty and stored for 24 hours.
The eligible "Offline Finding" feature uses the energy-saving Bluetooth connection of your lost device connection to communicate with other nearby Apple devices that have Bluetooth enabled. Best of all, the whole process works with end-to-end encryption.
With E2E encryption nobody can abuse the system. Hackers are unable to intercept and decrypt your device's location, you can not track snooping marketers in their stores, and even Apple does not see any data sent or received. Totally anonymous.
How Offline Search Works
Offline Search uses a background process called "Search Party" to periodically send and receive Bluetooth beacon signals. It can even be run while the device is in the sleep state. This happens with a limited impact on the battery for all the devices involved, so you should not notice any or only a small difference in power consumption.
Your device is assigned a temporary public encryption key, which changes frequently over time. This is because a static identifier could allow others to save it for tracking purposes. However, as it changes constantly, there is no way to abuse it.
If the lost smartphone, tablet, or computer has no Internet connection, it sends its public encryption key via Bluetooth to another nearby Apple device. This other device then uploads its own encrypted location data, along with the hash of your lost device's public key, to Apple's server to help you identify later. If you then use Find My iPhone, Find My iPad, or Find My Mac, you will be sent this encrypted location information and your device will decrypt it.
But right here is the catch. To use offline search, you must have at least two Apple devices with the same iCloud account and two-factor authentication. This is because all connected devices use the same private key and the same set of rotating public keys.
If you use my search on your non-missing device, the public key hash is uploaded to the Apple servers. Apple then automatically scans its servers for encrypted locations for a matching identifier. When the cryptographic identifier is found, Apple sends it back to your device, where your private key decrypts it.
Apple did not specify how often public keys are rotated or how the hashes are tracked. Since the hash of your missing public key device has probably changed since the location data was last uploaded, it does not match the current public key ID for your non-missing Apple device. Therefore, they are likely to store and keep a short history of previous public keys in order to find matches in those cases.
To verify that Offline Search is enabled
Find My iPhone, iPad, or Mac is enabled by default Before updating to iOS 13, iPadOS 13, or macOS 10.15 Catalina, Offline Search should already be enabled his. However, if only one of the devices had the "Find my service" feature turned on, but no other device, it might not be turned on automatically. To verify that it's enabled, check the following:
On iOS 13 and iPadOS 13:
On iOS 13 for iPhone or iPadOS 13, open the Settings app and tap the top of your name to access the Display Apple ID settings. Then tap Find My, and then Find My iPhone. On the next page, make sure "Enable Offline Search" is checked.
Open System Preferences and tap the Apple ID option to view your account information. Next, select "iCloud" in the sidebar and make sure "Find My Mac" is turned on in the list of apps. If you need to turn it on, check it and click "Allow" when prompted. With Find My Mac turned on, tap "Options" and make sure "Enable Offline Finding" is turned on.
Let's say you've left your MacBook in a public library or someone grabbed your open laptop when you went to the bathroom in a cafe. If it were open, it could connect to a hotspot to send location data. However, if it were closed, which most likely would be the case, it could send its public key to other devices via Bluetooth. A thief does not have much time to open the Mac and disconnect Wi-Fi and Bluetooth. So if you are fast, you have a good chance of finding it.
However, if your iPhone is stolen, the thief can turn it off or turn on airplane mode, disabling not only Wi-Fi and cellular connections, but also Bluetooth. In these cases neither "Send last position" nor "Offline search" are very useful. And now that offline search is in place, thieves are more likely to make sure that Bluetooth is disabled along with the other connections.