In-vehicle information communication system and authentication method

An information communication system configured from an in-vehicle communication device and an electronic control device which are installed in a vehicle, and an information processing device which is not installed in a vehicle,

• wherein the electronic control device comprises:
• an electronic control device storage unit which stores a common key that is shared with the information processing device in advance;
• a message generation unit which generates a message for use in authentication;
• a message authentication code generation unit which uses the common key and generates a message authentication code related to the message;
• and
• an electronic control device communication unit which sends the message generated by the message generation unit and the message authentication code generated by the message authentication code generation unit to the information processing device via the in-vehicle communication device,
• wherein the information processing device comprises:
• an information processing device storage unit which stores the common key;
• a message authentication code verification unit which performs authentication of the electronic control device by verifying the received message authentication code using the common key and the received message;
• a response code generation unit which generates a response code by encrypting a value based on the received message via symmetric key encryption with the common key;
• and
• an information processing device communication unit which, when the verification by the message authentication code verification unit is successful, sends the response code generated by the response code generation unit to the electronic control device via the in-vehicle communication device, and
• wherein the electronic control device further comprises:
• a response code verification unit which performs authentication of the information processing by verifying the received response code based on the common key.