Apple Platform Security
- Welcome
- Intro to Apple platform security
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- System security overview
- Signed system volume security
- Secure software updates
- Operating system integrity
- Activating data connections securely
- Verifying accessories
- BlastDoor for Messages and IDS
- Lockdown Mode security
- System security for watchOS
- Random number generation
- Apple Security Research Device
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- Services security overview
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- Apple Pay security overview
- Apple Pay component security
- How Apple Pay keeps users’ purchases protected
- Payment authorization with Apple Pay
- Paying with cards using Apple Pay
- Contactless passes in Apple Pay
- Rendering cards unusable with Apple Pay
- Apple Card security
- Apple Cash security
- Tap to Pay on iPhone
- Secure Apple Messages for Business
- FaceTime security
- Glossary
- Document revision history
- Copyright
iPhone cellular call relay security
When a user’s Mac, iPad, or HomePod is on the same Wi-Fi network as their iPhone, it can make and receive phone calls using the cellular connection on iPhone. Configuration requires the devices to be signed in to both iCloud and FaceTime using the same Apple ID account.
When an incoming call arrives, all configured devices are notified using the Apple Push Notification service (APNs), with each notification using the same end-to-end encryption as iMessage. Devices that are on the same network present the incoming call notification user interface. When the user answers the call, the audio is seamlessly transmitted from the user’s iPhone using a secure peer-to-peer connection between the two devices.
When a call is answered on one device, ringing of nearby iCloud-paired devices is terminated by briefly advertising using Bluetooth Low Energy (BLE). The advertising bytes are encrypted using the same method as Handoff advertisements.
Outgoing calls are also relayed to iPhone using APNs, and audio is similarly transmitted over the secure peer-to-peer link between devices. Users can disable phone call relay on a device by turning off iPhone Cellular Calls in FaceTime settings.