Patent ID: 7002449

Claim:
Keyless entry for executing immobilizer authentication, comprising: a plurality of mobile devices each capable of fitting thereto a transponder for immobilizer authentication; and a car-mounted device including a mobile device communication portion for communicating with said plurality of mobile devices and an immobilizer authentication portion for executing immobilizer authentication through communication with said transponders; wherein said immobilizer authentication portion includes a transmission/reception portion for executing communication by wireless signals with said transponders, an ID preservation portion for storing and preserving ID of registered transponders, and a combination ID preservation portion for storing and preserving a combination of an ID of a registered mobile device and an ID of a transponder fitted to said registered mobile device, a combination of an ID of a mobile device lastly making communication and an ID of a transponder is extracted from said combination ID preservation portion when said immobilizer authentication portion executes immobilizer authentication, and an immobilizer authentication process is executed first for a transponder having the ID so extracted.