Authentication system and authentication method

An authentication system comprising:

• an in-vehicle unit that is mounted in a vehicle;
• and
• a vehicle-exterior apparatus that is provided outside the vehicle,
• wherein
• the in-vehicle unit and the vehicle-exterior apparatus are configured to communicate with each other,
• the in-vehicle unit includes:
• a first vehicle-interior storage unit that stores user related information about a user who utilizes the vehicle;
• a second vehicle-interior storage unit that stores vehicle related information about the vehicle, and
• a vehicle-interior control unit that performs varied processing,
• the vehicle-exterior apparatus includes:
• a first vehicle-exterior storage unit that includes a shared area and a non-shared area for storing the user related information;
• a second vehicle-exterior storage unit that stores the vehicle related information, and
• a vehicle-exterior control unit that performs varied processing;
• the vehicle-interior control unit and the vehicle-exterior control unit perform synchronization processing for bi-directionally synchronizing the user related information stored in the first vehicle-interior storage unit and the user related information stored in the shared area in the first vehicle-exterior storage unit with each other,
• when utilization of the vehicle is requested from a user,
• the vehicle-interior control unit performs authentication processing to authenticate a target user, who requested the utilization of the vehicle, based on the user related information stored in the first vehicle-interior storage unit and the vehicle related information stored in the second vehicle-interior storage unit and, and when the target user is successfully authenticated by the authentication processing, the vehicle-interior control unit reflects the user related information corresponding to the target user in the vehicle, and
• at an information insufficiency time when information corresponding to the target user does not exist in the user related information stored in the first vehicle-interior storage unit or the vehicle related information stored in the second vehicle-interior storage unit, the vehicle-interior control unit or the vehicle-exterior control unit performs the authentication processing based on the user related information stored in the non-shared area in the first vehicle-exterior storage unit.