Explore UWB-based car keys

Highlight

The U1 chip of iPhone and Apple Watch supports UWB (Ultra Wideband) car keys to achieve a passive entry experience - without taking out the device, the vehicle automatically recognizes the user’s location and unlocks and starts; it also supports Remote Keyless Entry (RKE) control and key-based vehicle personalization.

Core Content

The evolution of digital car keys

WWDC2020 Apple launched a digital car key feature that allows users to unlock, lock and start their cars with iPhone or Apple Watch, share keys with family and friends, and even manage them remotely.The entire system is designed to be secure and private.(00:20)

WWDC2021 expanded the capabilities of car keys:

Passive entry.Using UWB technology, users can leave their iPhone in their bag or pocket and unlock, lock and start their car with their Apple Watch on their wrist.(00:55)

Remote Keyless Entry (RKE) Control.Users can use their iPhone or Watch to lock, unlock, or perform other operations within Bluetooth range.(01:08)

Personalization.The vehicle can be personalized by recognizing which digital key enters the vehicle through which door.(01:15)

Technical basis

These functions are realized by multiple technologies:

U1 chip and UWB technology.Allows the car to determine the precise location of nearby car keys.UWB is also the basis for secure ranging protocols, providing stronger protection against replay and relay attacks.(00:37)

Secure Element.A protected hardware unit integrated into an Apple device.In addition to storing car keys and authentication credentials, it is now used to derive session-specific UWB ranging keys.(00:51)

Bluetooth Low Energy (BLE).Serves as a communication channel between the car and Apple devices, exchanging data during authentication and managing secure ranging sessions.BLE is also used as an anchor point to initialize the secure ranging time grid.(02:06)

Industry Standard.Apple and other industry partners in the Car Connectivity Consortium are leading the development of standards specifications to ensure common solutions that are supported across platforms.(02:24)

Security and Privacy by Design

UWB passive entry solutions are designed with security and privacy in mind.(02:38)

Session Key.A unique key is derived for each connection.Some session keys are used to encrypt link layer messages, others ensure that the device cannot be tracked by UWB or BLE.

Random identifier.Use a random identifier derived from the session key and rotate it periodically.

Secure Ranging Protocol.This is a two-way ranging protocol implemented through the exchange of three data packets.Think of it as “ping-pong-ping”:

iPhone sends poll message
The car replies with a respond message
iPhone sends another poll message to improve accuracy

Each message carries a Scrambled Timestamp (STS), which is a cryptographically generated time-limited packet such that even authenticated packets can only be accepted in the timeslot in which it was accepted, providing additional protection against replay and relay attacks.(03:17)

Detailed Content

Virtual areas and passive entry

Each car defines a series of virtual areas.When a device with a valid and active key is positioned to enter or exit these areas, related functions can be triggered.(03:57)

Welcome Area.Activate welcome functions such as turning on the lights or warming up the cabin.

UNLOCKED AREA.Typically the area closest to the car, unlocking the door as the user approaches.

Car lock area.Lock the car when the user leaves.

Workflow of positioning devices

The car is equipped with multiple UWB and BLE transceivers ensuring 360-degree coverage to locate paired devices within the virtual area.(04:35)

When the user first approaches the car:

iPhone or Apple Watch detected via BLE
Establish a communication channel with the car
Car authentication equipment, both parties derive a shared ranging key
The derived key is used to initiate a secure ranging session with the UWB transceiver
Car positioning equipment and mapping its trajectory

The car continues to map the device’s trajectory.Based on location and trajectory, the car can decide to trigger welcome features, such as turning on the lights or adjusting the seats.When the device is positioned within the unlock zone, the car can initiate an unlock operation before the user touches the door handle.(05:35)

Know exactly whether the user’s device is in the car: The engine will only start when a device with a valid key is detected to be in the car.(05:53)

Battery reservation support.You can enjoy the UWB experience even when your phone is in battery reserve mode.If your phone needs charging after a day of hiking or backpacking, there may still be enough juice left in the battery to get the user back on the road.(06:07)

Remote Keyless Entry (RKE) Control

Remote operation is suitable for situations far away from the car.You can warm up the cabin in the winter or locate the car by honking its horn.Many actions can be triggered directly from the Wallet app.You can also use your device to view car information such as lock status, fuel level, or battery charge status.(06:30)

How RKE control works:

The device requests a challenge for the relevant operation
Challenge is used to generate device signatures
The car verifies the device signature based on the challenge, related operations and other information
If the verification is successful, the car performs the operation and notifies the device

Remote operations are sent over BLE.Being UWB independent, they work even outside UWB range.Remote operation is standardized in the Automotive Connectivity Alliance, with a common implementation across all cars and devices.(06:51)

Vehicle Personalization

Digital car keys can now automatically personalize settings such as cabin temperature, seat position, seat heating and more by observing which digital key is approaching the driver’s door.(07:42)

Traditional car keys rely on the driver to always know which key fob has which user settings.Now, with car keys on your iPhone or Apple Watch, there’s no need to worry about that.With precise trajectories and knowledge that personal devices are closely tied to users, cars can personalize experiences with more confidence than ever before.This works seamlessly even if multiple users approach the car.(08:04)

Automotive Manufacturer Integration Essentials

System Architecture.Passive entry solutions rely on reliable and accurate positioning, and the system must have good performance and low latency.(09:00)

Choose the right transceiver:

Ensure the transceiver provides sufficient link budget
Evaluate Tx radiated power and Rx sensitivity
Ensure the transceiver antenna supports the entire field of view required for coverage by fine-tuning the antenna directivity
Antenna diversity is essential to achieve good operating range

Transceiver placement:

Identify the best places to place transceivers around the car
Consider height and direction
Verify system RF performance
Ensure the system has sufficient link margin buffering

System delay.Upon approaching the car, a complex series of events begins that must be completed before the user attempts to open the door.High-performance cryptographic processors are required for authentication and key management, and the bus system connecting the ECU to each transceiver must be low-latency.(11:45)

Time synchronization.By enabling precise time synchronization, each transceiver knows the expected time of an incoming packet to an accuracy of tens of microseconds.Scan only within a time window, saving power and improving performance.(12:40)

Transceiver Synchronization.Transceivers that successfully synchronize with a device can share timing information with other transceivers, helping them connect quickly and even calculate time-of-flight when they fail to complete a full ranging cycle.(13:30)

Positioning Algorithm.This is the code that runs on the car’s ECU.The device’s distance from each connected UWB transceiver is collected and processed to locate the iPhone or Apple Watch in space.Positioning algorithms need to be fast and accurate, whether tracking a user’s approach to a car or determining whether a device is inside or outside the cabin.(14:02)

Recommended development workflow

UWB Interoperability.Make sure you follow specifications and test using tools provided by Apple
BLE layer integration.For connection management and owner pairing
Safety ranging management.Critical to passive entry
Remote operation support.for remote control

Vendors interested in development should participate in the Automotive Connectivity Alliance and join the MFi program for specific details on working with iPhone and Apple Watch.(15:11)

Core Takeaways

What: Build digital key experiences for automotive brands
Why it’s worth it: UWB technology allows car owners to unlock their vehicles without taking out their phones, providing a truly senseless entry experience.
How to get started: Join the MFi Initiative and the Automotive Connectivity Alliance and follow the recommended workflow starting with UWB interoperability and developing step by step
What: Enable location-based personalization
Why it’s worth it: By identifying which key enters through which door, you can automatically adjust personalized settings such as seat position, temperature, music preferences, etc.
How to Get Started: Track the device trajectory in a positioning algorithm to determine the key identifier approaching the driver’s side
What: Extend UWB technology to other smart devices
Why it’s worth it: UWB’s precise positioning capabilities are not only suitable for cars, but can also be used for smart home device positioning, room-level device control, etc.
How to get started: Study the Nearby Interaction framework and explore inter-device ranging and direction detection
What: Build a secure near field communication system
Why it’s worth doing: The security design of the car key (session key, random identifier, secure ranging) can be applied to other scenarios that require secure short-range communication
How to start: Refer to the security architecture of car keys, use Secure Element to store sensitive credentials, and achieve session key derivation
What to do: Optimize BLE + UWB hybrid positioning solution
Why it’s worth doing: BLE is used for rough detection and initial connection, UWB is used for precise positioning, and the combination of the two can balance power consumption and accuracy
How to start: First use BLE scanning to detect the proximity of the device, then start a UWB ranging session to pinpoint the location

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