remote keyless entry (RKE)

Remote keyless entry (RKE) is an electronic access system that can be controlled from a distance. RKEs, which are typically used to remotely lock or unlock doors, require the end user to initiate an action that will cause a physical or software key fob to transmit a radio signal to a receiver that controls an electronic lock. Typically, the action is to press a button on a physical fob or mobile app.

Remote keyless entry, which is commonly used to protect vehicles from theft, can be contrasted with passive keyless entry (PKE), which does not require any action on the part of the end user. Most RKEs operate at a frequency of 315 MHz for North America-made cars and at 433.92 MHz for European, Japanese and Asian cars. Modern systems since the mid-1990s implement encryption as well as rotating entry codes to prevent car thieves from intercepting and spoofing the signal. A controller chip in the receiver changes the exact frequency required for RKE each time the lock is accessed, a security feature known as rolling code or hopping code.

At a minimum, modern systems have 40-bit security, for a possible near-trillion rolling codes. The rolling codes are chosen by a pseudo-random number generator (PRNG) and the fob and lock controller are synchronized each time the fob is used. Because a new code is generated after each use, momentary access to a fob will not provide permanent access. The chance of opening a lock on another person’s car, given that they use the same RKE system for instance, is estimated to be about a one in a billion.

Other than controlling locks, RKE systems for cars can be used to control the vehicle's ignition system, security alarm, horn, lights and trunk. RKEs are also used to control entry to premises and specific areas of buildings, such as garages. While the use of RKE is uncommon on buildings outside of businesses, some home automation and security systems rely on the technology as well.