Patent ID: 7366677

Claim:
A car rental system comprising: a fleet of cars, each having an in-car access controller which is operable only when a valid digital key is presented to the car; a management system for handling reservation and car return, said management system including a reservation server and key generation system for generating digital keys for users of the car rental system, said key generation system storing a digital key on a portable storage device provided to a user of the car rental system, the digital key specifying a starting date and time of a rental transaction and identifying the car the digital key is for and personal information identifying the user; said information being digitally signed using a private key of the reservation server as a digital signature of the reservation server; the in-car access controller including means for reading the digital key on the portable storage device and verifying the digital signature of the reservation server and input means for receiving information identifying the user and comparing entered personal information with personal information identifying the user of the digital key, the in-car access controller further including means for invalidating the digital key if the entered personal information does not match the personal information identifying the user of the digital key but, otherwise, activating instruments which the user is authorized to have access to, the in-car access controller being responsive to a request from the user to return the car and including means for obtaining car status information, including fuel level, mileage, current time and car ID, and generating a return packet by combining car status information and current digital key and signing the return packet using a private key of the in-car access controller as a digital signature and saving the return packet on the portable storage device; and a key return system for processing digital keys returned by renters, the key return system invalidating the current digital key and printing a receipt for the user.