There is provided a mobile terminal for use in a system which includes a backend server having a first encryption key and an onboard unit (OBU). A first receiving unit receives, from the backend server, a base shared key encrypted with a second encryption key, the base shared key encrypted with the first encryption key, and a digital signature. A deriving unit decrypts the base shared key with the second encryption key and derives first authentication information based on the base shared key and a first temporary parameter. A second sending unit sends, to the OBU, the base shared key encrypted with the first encryption key, the digital signature, the first authentication information, identification information of the base shared key, and the first temporary parameter.