The Connected Key is the future. It allows the implementation of several new features and applications, and stores all the car information, tour programmes, and importantly offers connectivity.
The car key has come a long way. Today's car keys include so much technology that their relationship to car keys of just a decade ago can barely be recognised.
Electronics in car keys started out with the vehicle immobiliser. Car theft rates were increasing drastically during the early 90s and insurance companies demanded action from the carmakers. At the same time, the first RFID applications were coming into use for wireless identification. NXP Semiconductors realised that the same basic technology could be used to identify whether a key belongs to a car via a wireless passive RFID interface. Compared to a mechanical key, this greatly increases the security of vehicles against theft and was quickly adopted.
At the same time remote keyless entry gained popularity. Car owners appreciated the comfort of locking and unlocking their car from a distance by the push of a button. This application requires a fully printed circuit board with battery incorporated in the small space available in a key. To reduce space requirements and provide cost advantages, combi-chips that integrate remote keyless entry with immobiliser functionality were introduced. The most advanced of these chips can even be integrated with a transmitter.
Even more comfort is provided to the driver by a Passive Keyless Entry / Go system first introduced in 1999 on the Mercedes S-Class. Here, the driver does not need to use the key to open the car. Instead, when reaching for the door handle, sensors initiate communication between the car and the key, verifying whether the key belongs to the car. When the driver is inside the vehicle, pressing the start button initiates communication between the car and the key. The car checks whether it is the right key and whether it is inside the vehicle.
The story of adding comfort to the driver through the car key continues with two-way communication car keys. The standard remote keyless entry system sends information only in one direction. The key does not receive confirmation whether the car was really locked. By adding a return link, the car can immediately provide feedback on its locking status to the key. If the driver later wants to check whether he locked the car or not, he can get the information simply by pressing a button. Many more features like improved security are enabled by adding this return link.
Today, Passive Keyless Entry and Go systems are available for more than 200 car models, sometimes as a standard feature. Car keys with bi-directional communication have begun to appear as well, with the Volvo S80 being one example. Naturally the technology leaders in this area have started to think about the key of the future. What will be the next big thing? Many believe the answer is the same that is often given in other areas of technology: Connectivity.
Functions and communication technologies
Today a fully featured car key comprises the following features and functionality:
• Immobiliser
• Remote Keyless Entry (RKE)
• Passive Keyless Entry / Go (PKE / PKG)
Figure 1 depicts the communication interfaces utilised in the above car key features.
An immobiliser system typically consists of a transponder, which is embedded in the car key, and a base station that is connected to the car's engine control unit (ECU). When the driver inserts the key into the key slot and turns the key to start the engine, the engine control unit initiates the authentication with the transponder. The engine control unit and the transponder of the car share a secret key. During authentication, the engine control unit sends a random number and the ECU authentication code to the transponder. When the ECU authentication code matches the expected one, the transponder returns the ciphered random number to the vehicle for verification.
After the ECU has successfully validated the transponder identity, the engine gets started. Since both the car (the ECU) and the key (the transponder) authenticate each other, this authentication process is called mutual authentication.
Not all the immobiliser transponders in the market employ mutual authentication. Some also utilise the so-called challenge-response procedure. In this case, only the car authenticates the key by sending a challenge to the key and verifying the key's response. As the key does not verify the authenticity of the car and therefore the challenge, the challenge response pairs can be easily collected and filed for attacks.
Typically, an immobiliser system utilises low frequency (LF:30-300 KHz) communication. Typical frequencies for the LF communication are 125kHz, e.g. the NXP Hitag-2 solution, and 134.2kHz, e.g. the TI DST solution. Besides data communication, the LF link also serves the purpose of supplying the transponder with energy. When the key is in the key slot, the transponder and the base station antennas form a loosely coupled transformer, which enables the transponder to induce energy from the LF signal for its entire operation.
Immobilisation systems are required by insurance policies in many countries in Europe and North America, and are a standard component of passenger cars sold in these markets. In some other regions, such as China and India, the immobiliser system was introduced just a couple of years ago. In India, the government will soon enforce the immobilisation systems in all passenger cars to be sold in the domestic market.
Remote Keyless Entry systems use a unidirectional UHF link, typically in the ISM (Industrial, Scientific and Medical) band with 315 MHz, 434 MHz and 868 MHz. When a button is pressed, the key fob transmits a telegram to the car using this UHF link. The car verifies the fob identity, evaluates the button command and performs the requested operation.
The telegram contains a ciphered data string representing the button command, the key identity and a rolling code. The rolling code is maintained by both the key and the receiver and has to be always kept synchronised. The rolling code serves as a random number for generating the ciphered telegram data, in order to prevent the attackers from eavesdropping and replaying valid telegrams.
The counter values get out of synchronisation when, for example, a fob button is pressed too many times while the fob is away from the car. When this takes place, the system needs to be resynchronised at service stations. However, if the key utilises a combi-chip solution, in which the immobiliser and the RKE functions are integrated in one chip, the resynchronisation can easily be performed via the LF immobiliser interface without any intervention from the driver.
Currently, bi-directional RKE systems are under development. The so-called two-way key will enable feedback from the car after a button command has been executed and will contribute to the enhancement of system security.
At an even higher level of chip integration, the Passive Keyless Entry / Go (PKE / PKG) function can be integrated on the same chip as the immobiliser and the RKE.
The PKE / PKG system enables the driver to enter the car by simply pulling the door handle and to start the engine by simply pressing the ignition button in the dashboard, without the need for taking the car key out of the pocket.
A PKE system consists of one or more key fobs, each with an LF receiver and a UHF transmitter while the car has several LF transmitters and a UHF receiving module. The PKE system utilises the LF link for data communication from the car to the key and the UHF link from the key to the car.
In a passive keyless entry application, the driver approaches the car and pulls the door handle. The car is triggered by this event and transmits a wakeup pattern to the key. Afterwards, the car and the key mutually authenticate each other in the same way as in an immobiliser system. The car door is unlocked if the authentication completes successfully. The PKG application is very similar to the PKE application. The mutual authentication starts when the ignition button is pressed and the engine is started upon successful authentication.
While the aforementioned car security and comfort applications will continue penetrating the markets, which they have not reached yet, the leading automotive chip manufacturers, system suppliers and car OEMs are already looking ahead and thinking what more to offer in the car keys in future. The Connected Key appears to be the answer.
On top of the existing car key functions, the Connected Key provides the connectivity of car keys to other devices, such as mobile phones, PDAs or PCs. The connectivity is enabled by the Near Field Communication (NFC).
The NFC technology enables wireless short range connectivity between electronic devices. It is standardised under ISO18092 and is driven by the NFC Forum. The communication works at 13.56 MHz and has a data rate of up to 424 Kbits per second. Communication between NFC-enabled devices takes place when they are brought close to each other. The need for close distance gives the system security as well as a very intuitive "touch". Devices can be "active" i.e. battery powered, as well as "passive", not requiring a battery, absorbing energy from the field of an active NFC device. An NFC-enabled car key would be a passive device and thus this feature would not require additional battery power. NXP Semiconductors is working together with major automotive suppliers to bring this technology into the car keys of the future.
The Connected Key allows the implementation of several new features and applications. First, it can be used to display car related information on a mobile phone. For example, the driver can find out if he needs to refill the fuel tank even before entering the car. The key could also connect to other devices, such as reader stations to authorise services or discounts at a car dealer, a gas station or a shop.
You might have experienced the inconvenience of planning your trip on your in-car navigation system. With a connected key, you may now comfortably plan your trip on a PC and afterwards store the route information directly into the key via an NFC reader. When you enter the car, the route information will be loaded automatically into the in-car navigation system. All you need to do is to press the ignition button and start your journey.
As more and more mobile phones and cars are equipped with navigation technology, another very interesting application for the connected key-the car finder-becomes possible. Many people undergo the distressing experience of having parked the car on a huge parking area, possibly in a foreign city, and trying to find it back later. The navigation system of the car could store the parking position on the key. When trying to find the car, a simple touch of the key to the mobile phone will enable the display of the car location. Using the GPS system of the mobile phone, the key can guide the driver back to the car.
The Connected Key is often compared to a key with a display. However, Connected Key offers more benefits over the key with a display. The Connected Key does not require an internal display and so does not need an additional battery. Also, the display in a key would need to be to be especially rugged and scratch resistant, e.g. to survive a drop on a concrete floor or withstand other keys scratching the display. Finally, a mobile phone display is larger and can show more information in comparison to what would be possible on a small key display.
For the Connected Key to be successful, an NFC infrastructure is required. This is still an ongoing process. Field trials all around the world are rendering positive results. NXP Semiconductors and SONY have set up a joint venture called Moversa. This new company is developing a Secure Access Module. When brought together with an NFC chip, this will enable a universal contactless IC platform for mobile phones that can be used globally.
As we have seen, today's car keys have many communication interfaces. Adding another interface like NFC, which is standardised, enables many new features. Especially, processing and displaying car related information with an NFC-enabled mobile phone brings a whole range of new possibilities. The process of establishing an NFC infrastructure is gaining momentum and is fundamental for the future of the Connected Key.
Huanyu Gu is the technical business development Manager for Car Access and Immobilization at NXP Semiconductors. He holds an MSc in Information & Media Technologies from Hamburg University of Technology and an MBA in Technology Management from Northern Institute of Technology Hamburg. Prior to the current position, Huanyu Gu was the Customer Application Support Engineer, providing support in Tire Pressure Monitoring Systems, Remote Keyless Entry Systems and Passive Keyless Entry Systems to industrial customers.
Sebastian Schreuder is the marketing manager of Car Access and Immobilization at NXP Semiconductors. He holds a Masters in Electrical Engineering from the Univierstiy of Karlsruhe and an MBA degree from the Collège des Ingénieurs, Paris. Schreuder has also worked as the Junior Consultant for Project and Process Management at Daimler.
