Phone as a Key – How does the Huf digital car key work?

High localization accuracy with UWB - what is Ultra Wideband?

Typically, radio technologies utilize continuous signals. UWB, on the other hand, only sends short pulses. To put it metaphorically, conventional radio transmissions can be thought of as long flute melodies, whereas UWB is like short drumbeats that produce a fast echo. These UWB pulses span a very wide frequency range - hence the name "ultra wideband".

UWB achieves a high localization accuracy for real-time localization systems. Using pulses of short duration, it can detect the position of an object in a room with an accuracy of just a few centimeters. At the same time, UWB can be used with other radio technologies such as WLAN and Bluetooth in the same environment.

How is the smartphone position localized via UWB with the digital car key?

To achieve a precise localization, Phone as a Key by Huf uses UWB from a distance of about ten meters between the smartphone and the vehicle to position the mobile device carrying the digital car key. This is realized using in-car transmitting/receiving units known as satellites. Ideally, four of them are located in the "corners" of the vehicle, as this enables them to localize the mobile device very precisely under almost all conditions.

Two additional UWB satellites are installed in the passenger compartment. Thus, Phone as a Key provides highly accurate localization and meets all critical requirements. The rearmost of the two UWB satellites in the interior can be integrated into the roof lining and can thus also be used to monitor the rear seats and the trunk. This opens up possibilities for additional functions, especially for advanced safety systems such as Child Presence Detection by Huf.

How does UWB protect against hacking and relay station attacks on smartphone car keys?

Phone as a Key meets the highest safety standards. One reason for this: UWB makes it possible to measure the "Time of Flight" (ToF). The individual UWB components - smartphone and satellite - each measure the time it takes for the signal to travel from the transmitter to the receiver. Thus, each component can calculate the distance between the two components based on the time measurement. An attacker who extends the signal from the vehicle to the smartphone would also extend the ToF as a result. This makes relay station attacks - where hackers intercept and relay the signal from a key to the vehicle - virtually impossible.

Moreover, data sent via UWB is obviously encrypted. Even if an attacker managed to intercept a signal, the data in it would be useless without the right code. This is because modern UWB systems, such as Phone as a Key by Huf, use secure protocols to exchange keys between devices. Attackers would not be able to extract or copy the codes they contain.

NFC for car access in case of emergency

Even today it is possible that the smartphone battery runs out. Nevertheless, in this case, car owners must be able to access their vehicle and start the engine. Of course, Huf has also thought of this scenario: Phone as a Key therefore uses NFC technology as a fallback solution for car access. Huf was the first automotive supplier worldwide to introduce this into a vehicle, making it possible for the first time to open the car with a smartphone.

NFC transceivers can be installed in door handles, in the B-pillar, as well as in the interior of a vehicle, for example. By holding the smartphone up to the NFC transceiver, the smartphone's NFC chip - which features an integrated secure element - is supplied with the necessary energy to authenticate the digital car key in the smartphone. This allows the vehicle to be unlocked.

AUTOSAR compatibility ensures compatibility with vehicle architectures

In modern vehicles, many different technologies and software come together that have to work hand in hand, communicate with and complement each other - without, of course, leaving any security gaps open. Automobile manufacturers and automotive suppliers must therefore ensure that their components can be integrated into a wide variety of vehicles worldwide.

This can only be achieved if there is a common technological basis. The goal of the Automotive Open System Architecture development partnership, or AUTOSAR for short, is to develop the necessary standards. This project of car manufacturers and suppliers from numerous related industries was founded in 2003 to address the growing complexity of electronic systems in vehicles. The result of this collaboration is an open, scalable software architecture for electronic control units (ECUs) in vehicles.

Phone as a Key by Huf complies with numerous important standards. And needless to say, the system is also AUTOSAR-compliant. The localization and key management software can thus be easily integrated into corresponding vehicle architectures.