Apple Platform Security
- Welcome
- Intro to Apple platform security
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- System security overview
- Signed system volume security
- Secure software updates
- Background Security Improvements
- Operating system integrity
- BlastDoor for Messages and IDS
- Lockdown Mode security
- System security for watchOS
- Random number generation
- Communicating emergency information using satellites
- 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
- SharePlay security
- Nearby sharing security
- Glossary
- Document revision history
- Copyright and trademarks

Physical pairing model security for iPad and iPhone
iOS and iPadOS use a pairing model to control access to a device from a host computer. This establishes a trust relationship between the device and its connected host, signified by public key exchange. iOS and iPadOS also use this sign of trust to enable additional functionality with the connected host, such as data syncing. On an iPhone with iOS 9 or later or an iPad with iPadOS 13.1 or later, services:
That require pairing can’t be started until after the device has been unlocked by the user
Won’t start unless the device has been recently unlocked
May (such as with photo syncing) require the device to be unlocked to begin
The pairing process requires the user to unlock the device and accept the pairing request from the host. On an iPhone with iOS 9 or later or an iPad with iPadOS 13.1 or later, the user is also required to enter their passcode, after which the host and device exchange and save 2048-bit RSA public keys. The host is then given a 256-bit key that can unlock an escrow keybag stored on the device. The exchanged keys are used to start an encrypted SSL session, which the device requires before it sends protected data to the host or starts a service Finder or Music app syncing, file transfers, Xcode development, and so on. To use this encrypted session for all communication, the device requires connections from a host over Wi-Fi, so it needs to have been previously paired over a physical connection (Thunderbolt or USB). Pairing also enables several diagnostic capabilities. On devices with iOS 11 and iPadOS 13.1, or later, if a pairing record hasn’t been used for more than 30 days, it expires.
Certain diagnostic services, including com.apple.mobile.pcapd, are restricted to work only over USB. Additionally, the com.apple.file_relay service requires an Apple-signed configuration profile to be installed. On devices with iOS 11 and iPadOS 13.1, or later, Apple TV can use the Secure Remote Password protocol to wirelessly establish a pairing relationship.
A user can clear the list of trusted hosts with the Reset Network Settings or Reset Location & Privacy options.