Passive keyless entry (PKE) is an automotive security system that operates automatically when the user is in proximity to the vehicle, unlocking the door on approach or when the door handle is pulled and locking it when the user walks away or touches the car on exit. PKE systems are also used to secure buildings or areas of buildings.
A PKE device can operate while stored in the user's pocket or bag, unlike a standard remote keyless entry (RKE) device, which requires the user to hold the device and push a button to lock or unlock the vehicle. Passive keyless entry systems typically involve an RF (radio frequency) key fob but there are also smart cards and mobile apps designed for PKE.
The PKE key fob and the vehicle module both contain transceivers that communicate wirelessly to detect each other. The module in the vehicle continually sends out encoded messages; when the key fob is in range it responds. If the encrypted messages are correct, they identify the vehicle and key fob to each other and the door opens. Current PKE systems often use rolling codes to ensure that a fresh code is supplied each time, preventing the possibility of a replay attack.
Cars that are designed for passive keyless entry often feature keyless start as well, which simply requires the driver to push a button. (That combination is sometimes called passive entry/passive start or PEPS.) Individual smart keys may be customized for specific drivers, adjusting seat and mirror positions automatically, for example, or setting the car's radio to the driver's chosen station.
Siemens, a German manufacturing and electronics company, developed the first PKE system in the mid-1990s, and Mercedes-Benz implemented it under the name of "Keyless Go." There are a great number of other names for PKE systems and they vary from one manufacturer to another.