Information update system and method, vehicle, charger and server apparatus

An information update system is provided with a vehicle (10), a plurality of charger (20), and a server apparatus (30). The vehicle applies a first signature to position information associated with the vehicle, and transmits to a charger when a battery is charged. The charger applies a second signature to the position information with the first signature applied thereto. The charger further transmits, to the vehicle, identification information associated with the charger with a third signature applied thereto. The vehicle further applies a fourth signature to the identification information. The vehicle or the charger transmits to the server apparatus the position information with the first signature and the second signature applied thereto, and the identification information with the third signature and the fourth signature applied thereto. The server apparatus updates stored position information on the basis of the transmitted position information and the transmitted identification information.