Keyless Entry & Immobilizers
From simple radio remotes to Passive Keyless Entry (PKE) and smartphone integration. Modern systems use rolling codes, encrypted communication, and UWB to prevent theft and relay attacks.
The Evolution of Car Keys
Before keyless entry, cars used simple metal keys that mechanically engaged tumblers in the ignition and door locks. Theft was as simple as hotwiring— bypassing the ignition switch entirely. The introduction of electronic security changed everything.
Remote Keyless Entry (RKE)
The first remote keyless entry systems used a simple radio transmitter in the key fob sending a fixed code to a receiver in the car. Pressing the button would unlock the doors. These systems were vulnerable to replay attacks—recording the signal and playing it back to unlock the car.
Rolling Codes
To defeat replay attacks, manufacturers introduced rolling codes (also called code hopping). The fob and car share a synchronized algorithm that generates a new code for each transmission. Even if an attacker records the code, it won't work again. The system typically uses AES-128 encryption and advances the counter after each successful use.
Passive Keyless Entry (PKE)
PKE detects when the authorized key is near the vehicle (typically within 1-2 meters) and automatically unlocks doors when the driver touches the door handle. The car sends a challenge to the key, which responds with a cryptographic signature. This convenience came with a new vulnerability: the relay attack.
Relay Attacks
In a relay attack, thieves use a pair of radio devices to extend the PKE signal from the victim's key (inside their home) to the car parked outside. The car thinks the key is present and unlocks. This attack, costing UK insurers over £1.5 billion annually, led to new countermeasures.
Ultra-Wideband (UWB) PKE
The latest generation of PKE uses Ultra-Wideband (UWB) technology. UWB transmits at extremely low power across a wide frequency spectrum, making it resistant to relay attacks. More importantly, UWB can measure the precise distance to the key, ensuring it's truly near the car rather than merely relaying a signal from blocks away. Apple, Samsung, and BMW have deployed UWB digital car keys.
Immobilizers
Immobilizer systems prevent the engine from starting unless the correct transponder chip is present in the key. When the driver turns the ignition, the car sends a coded signal to the chip in the key. If the chip doesn't respond with the correct code, the fuel pump and ignition are disabled. Since their introduction, vehicle theft in equipped countries dropped significantly.