Communication system, vehicle-mounted terminal, roadside device

A vehicle-mounted terminal that transmits and receives information from one of a roadside device and another vehicle-mounted terminal, the vehicle-mounted terminal comprising:

• a storage portion configured to store a first list of vehicle-mounted terminals having valid certificates according to place and time and a second list of vehicle-mounted terminals having invalidated certificates;
• and
• a signature generation/verification portion configured to:
• omit certificate verification and discard a received message in response to receiving the message from a sender on the second list;
• omit certificate verification and verify a signature in response to receiving a message from a sender on the first list;
• and
• a processing portion configured to:
• confirm an effective place and an effective time in the first list and the second list, and in response to the vehicle-mounted terminal existing outside the effective place and/or exceeding the effective time, delete the first list and the second list.

A roadside device that transmits and receives information from a vehicle-mounted terminal, the roadside device comprising:

• a storage portion configured to store a first list of vehicle-mounted terminals having valid certificates according to place and time and a second list of vehicle-mounted terminals having invalidated certificates;
• a signature generation/verification portion configured to:
• omit certificate verification and discard a message received from a certain vehicle-mounted terminal in response to the second list listing the certain vehicle-mounted terminal;
• and
• omit certificate verification and verify a signature in response to receiving a message from a sender on the first list;
• and
• a processing portion configured to confirm an effective time in the first list and the second list, and delete the first list and the second list in response to the roadside device exceeding the effective time.