For specifications refer to the Car Connectivity Consortium.
What’s Car Keys?
With Car Keys you can lock, unlock and start supported cars via iPhone and Apple Watch.
Securely stored on device and iCloud
Shareable and manageable remotely
Supports multiple radio technology: NFC (for now), Ultrawide-band soon
Designed to work without a network connection
Works with Power Reserve (aka even when your device is out of battery and switched off)
Car compatibility
Three requirements:
Owner pairing
Transactions
Server interfaces
Owner pairing
Required to setup (additional) car keys on the iPhone.
Steps:
the user must prove ownership of the car (this step is up to the automaker)
initiate pairing (via app or email by automaker)
place iPhone nearby the car radio sensor
Car key appears in Wallet.app
Transactions
Used to lock. unlock, and start the car engine
Cars are required to provide radio sensors in the door handle and dashboard
Express mode
makes the transaction work without user identification first (face/touch id or password)
on by default, the user can turn it off
completely offline
No data is sent to Apple (a.k.a Apple doesn’t know when the user uses the car)
Service interfaces
required for car key sharing and management
Share keys via Messages.app
The car can be offline when the sharing happens
Fully encrypted: Apple has no info who the user shares the key with
Automakers can provide different access levels to different car keys, for example to limit the car speed
Key Management
the owner can create, manage, revoke, and share keys on iPhone
some functionality can be added in the dashboard
car keys removed on iPhone stop working immediately, even if the device is offline
iCloud lost mode temporarily suspends car keys on iPhone or Apple Watch (by locking the car key applet on the Secure Element)
when purchasing a new phone, the owner needs to pair the new device to the car and all previous keys will be automatically transferred, shared keys will keep working seamlessly
System Architecture
All key management is integrated in iOS, doesn’t relay on automakers
keys are created and stored on Secure Element (NFC/ApplePay chip)
use AES and Elliptic curve (EC) cryptography
Offline design based on PKI (Public Key infrastructure)
Automaker TSM (Trusted service manager) not required
Key lifecycle
Elliptic curve private/public key created in the device’s Secure Element
The private key never leaves the Secure Element
The public key is exported in a X.509 certificate for authenticity certification
A Secure Element Applet implements the car key:
stores key pair and binds it to the car
implements transactions and manages secure mailboxes which store key attestations and security tokens that prevent a revoked car key from being re-activated
Mailboxes also support immobilizer tokens for compatibility with existing car architectures
For memory efficiency all car keys are hosted in a single applet instance
