AUTONEWS
Keyless entry? Why your car might be vulnerable to theft
An increasing number of cars are equipped with keyless technology, a feature that is becoming widespread and appearing in more affordable models. While security has improved, not all vehicles are immune to vulnerabilities.
In short, "keyless" means exactly that—no physical key is required. You do not need to insert a key, remote, or card into a lock to open the vehicle; simply having the device nearby or inside the car is sufficient. When you walk away, the car locks automatically.
There is also no traditional ignition slot; the engine typically starts with the push of a button. The technology relies on radio waves and unique codes.
Naturally, this makes such systems potentially more vulnerable to silent theft than traditional key systems. With the right equipment and proximity to the key, a thief can amplify the signal to unlock and start the vehicle—according to the ADAC, one of Europe's largest automobile clubs.
Over the past decade, the club has tested 850 cars with keyless technology. It concluded that while 70 percent offer better theft protection, many remain vulnerable to attacks.
The use of Ultra-Wideband (UWB) chips—leveraging digital radio technology—has bolstered security in various models, preventing illicit entry even when signal extenders (as tested by the ADAC) are used. However, the club notes that its tests reveal "many vehicles can still be easily opened and stolen."
The automobile club found a lack of protection against keyless system exploits across several brands—ranging from the Stellantis Group (such as Alfa Romeo, DS, Fiat, and Opel) to Tesla, as well as BYD, Alpine, and Honda. Conversely, security improvements were observed in vehicles from manufacturers like Jaguar Land Rover and the Volkswagen Group (including brands such as Audi, Seat, Skoda, and Volkswagen). One of the security measures implemented by some manufacturers is a motion sensor that allows the radio signal to be deactivated after a certain period of inactivity. However, the ADAC warns that it is still possible to intercept the signal while it is active, meaning this is not the most robust measure.
Keyless entry and ignition systems began to appear in production in the late 1990s and early 2000s, and were initially available only on luxury models and other high-end vehicles. Since then, remote/passive keyless entry (RKE/PKE) features have become standard equipment on the vast majority of vehicles sold.
The popularity and convenience of keyless entry technology are indisputable. However, like many other technology-driven advancements, RKE/PKE systems are susceptible to attacks from hackers – and in this case – car thieves.
As car theft continues to surge, keyless entry security has become a priority for vehicle manufacturers (OEMs) and automotive cyber security experts are working to find ways to mitigate this threat. This post examines the nature and evolution of RKE/PKE attacks, why these technologies are potentially vulnerable to hackers, as well as the measures OEMs can take to mitigate RF attacks and strengthen the overall security of their vehicle fleets.
Remote Keyless Entry (RKE) Systems and Theft Vulnerabilities...Remote keyless entry refers to entering the car without using a physical key (e.g., using a door keypad or fob). The first RKE key fob used a coded pulse signal generator and a battery-powered infra-red radiation emitter. It was configured to transmit a specific signal, and the car was programmed to respond to that signal.
The replay attack...Taking advantage of this unprotected signal, hackers devised the “classic” replay attack, which uses a device to record and transmit at the same IR frequency as the key fob. When the driver presses the unlock button, the attacker records this signal and can then replay it at a later time to unlock the doors. Note that this hack can only work if the key fob uses the same unlock signal each time the unlock button is pressed.
To prevent such an attack, a rolling code field was introduced into the message sent from the fob to the car to make sure the unlock signal does not repeat. The car and the key fob share two code sequences – one for unlock and one for lock. For example, Xn would be the nth rolling code for unlock while Yn would be the nth rolling code for lock. All sequences are defined using a Cryptographically Secure Pseudorandom Number Generator (CSPRNG). When pressing the unlock button for the nth time, the key fob transmits code Xn. The car then compares the received rolling code with the expected rolling code, unlocking or locking the car accordingly.
The next wave of RKE attacks: The roll jam attack vulnerability...This security improvement triggered a new wave of “roll jam” attacks, which were designed to bypass these rolling codes. Roll jam attacks record the rolling codes and jam the RF signal from the key fob, preventing it from reaching the car. This attack scenario consists of the following steps:
The driver presses the unlock button, transmitting X1 which is the first code to unlock the car. The attacker jams the signal and learns the value of X1. The car doesn’t receive the signal due to the jamming and remains locked.
From a security standpoint, the main weakness in the implementation above is that the Lock and Unlock rolling codes are independent of each other. However, simply sharing the rolling code opens up new variations of the roll jam attack. The attacker can still jam consecutive messages, take the rolling code of an unlock command, and then construct a valid lock command (or the reverse scenario beginning with a jammed lock command and constructing an unlock command). Therefore, in addition to sharing the rolling code it is important to sign or encrypt the messages to make sure the attacker can’t construct messages based on the jammed rolling code. This can be done using a recognized and cryptographically secure message authentication code (MAC), such as AES-CMAC or HMAC, with a long shared secret key.
Passive Keyless entry (PKE) systems and security vulnerabilities...Passive keyless entry (PKE) took convenience to a higher level by allowing drivers to enter and start the car without having to take the fob out of their pocket. Building on lessons learned from RKE, a basic PKE communication consists of a challenge transmitted by the car to verify the identity of the key fob and a cryptographically calculated response transmitted by the key fob.
In most PKE implementations, the key fob and car share a long random secret key used to generate and verify the response. The key fob executes a cryptographic function on the challenge, generating the response which is subsequently verified by the car.
The relay attack...Since PKE implementations are based on proximity of the fob, they have an inherent constraint related to the distance the transmitter can reach. The infamous “relay attack” was devised to bypass this distance limitation. Consider a pair of attackers working together. One attacker is near the car and the other is in close proximity to the key fob. Each attacker uses a transceiver that operates over long distances (e.g., via 4G or WiFi) to forward the messages transmitted by the car and the fob.
As depicted below, Attacker A triggers the challenge and forwards it to Attacker B, who then transmits it to the key fob. The key fob answers the challenge and Attacker B forwards it to the Attacker A, who then retransmits it to the car.
PKES Security: Best practices for mitigating passive keyless entry vulnerabilities(below):
Mitigation #1: Set upper bound on response time...One method for mitigating relay attacks is to set an upper bound on the response time. Since waves are propagated at the speed of light, it’s possible to estimate an upper bound of the distance by measuring round trip time from the car’s challenge transmission until the response reception. Using UWB technology, a highly accurate measurement can be achieved.
Mitigation #2: Use RSSI to estimate key fob location...Another mitigation method is to estimate the key fob location using RSSI (received signal strength indicator), which identifies the distance between fob and car by signal strength. The car transmits the challenge from multiple antennas. The key fob then responds with the RSSI values of each of the antennas, and the car will use those values to estimate the location.
However, there are still ways for hackers to “outsmart” the location estimation algorithm. Since RSSI is measured on the key fob side, a pair of attackers may try to transmit an amplified challenge signal near the key fob to enlarge the RSSI values and “trick” the car into believing the key fob is closer than it really is.
Another issue with this mitigation method is that its values are not signed or encrypted. That means a digital attacker could use a demodulator to extract the data transmitted, modify the RSSI values and then modulate the signal again. If you’re using RSSI for localization, it’s recommended to sign or encrypt these values.
Mitigation #3: Integrating motion sensor...To try to prevent relay attacks, some key fobs integrate motion sensors to detect long IDLE periods. If after a couple of seconds/minutes no motion has been detected, the key fob stops answering challenges. In other words, if your key fob is on the kitchen table all night, an attacker can’t perform a relay attack on your car.
Known challenge relay attack...Another theoretical hacking scenario is a Known Challenge Relay Attack, which exploits implementations where the challenges are predictable. For example, the next challenge is the previous challenge plus 1: 0, 1, 2, …, 0xFFFFFFFF, or challenges are generated using a random number generator function that is not cryptographically secured, such as LCG, LFSR, etc. In such a case, an attacker who knows the PRNG function or guessed it correctly could construct the full challenge sequence.
Like the classic relay attack (described above), in this scenario the key fob and the car are distant from one another, but this time there is only one attacker. He triggers the challenge from the car and then tries to predict the next challenge the car will transmit. The attacker then moves close to the key fob and transmits the predicted challenge. The key fob answers with a response. Then, the attacker goes back to the car and triggers another challenge. If the triggered challenge is what the attacker predicted, the attacker can solve it by transmitting the response recorded from the key fob to unlock and start the car.
One strategy to consider for preventing this scenario is to make sure the challenges are not predictable by using a recognized CSPRNG with high entropy seed. Another suggestion is to have the car sign all challenges. In this way, even if the attacker is able to predict the challenge, he can’t query the key fob for the response.
Keyless entry security: Secure implementation is the name of the game...Vehicle theft has been a problem ever since cars were invented. Today, the cat-and-mouse game between security professionals and thieves continues – the only difference being the sophistication of the tools being used.
RKE and PKE create numerous security challenges for OEMs. We’ve seen that insecure RKE implementations are exposed to different variations of replay and roll jam attacks, such as the recently discovered Rollback attack. Messages should be signed or encrypted to prevent an attacker from modifying messages recorded from the key fob.
With respect to PKE implementations, it’s important to make sure challenges are not predictable by using a high entropy seed for randomization and applying CSPRNG to generate encrypted challenges. If you’re using RSSI to estimate location, these values should also be signed or encrypted to prevent tampering.
Moreover, some faulty implementations are mitigatable by upgraded security countermeasures. In many cases, a software update for either the BCM and/or key fob may be enough to fix known vulnerabilities. For this reason, OEMs that offer an Over-The-Air update feature are best-equipped to efficiently respond to the inevitable next attack.
There is no silver bullet for preventing keyless car theft, but proper implementation of the mitigation methods and practices described above would serve as a strong baseline for averting the vast majority of keyless entry hacking attempts.
Keyless entry security requires an AI-driven proactive Approach...Traditional anti-theft systems cannot stop keyless theft techniques that exploit the connectivity, in-vehicle networks and software vulnerabilities in today’s vehicles. Mitigation of these types of theft techniques dictates the need for proactive, adaptive and intelligent systems based on cybersecurity expertise.
PlaxidityX vDome is a comprehensive, AI-powered anti-theft service designed to actively protect vehicles from modern tools for keyless theft techniques. By combining the powerful TDPX in-vehicle agent with continuous cloud-based threat intelligence (VPCC), the vDome system stops CAN injections, key fob replications and emulator attacks at the source – before the engine even starts.
