Controller, communication method, and communication system

A communication method performed by a control circuitry when the control circuitry performs encrypted communication with a device which has succeeded in mutual authentication using an electronic certificate, the method comprising:

• determining by the control circuitry whether or not a communication target device with which communication is to be performed is an authentication support device that supports the mutual authentication;
• determining whether or not the communication target device is an authorized device when the communication target device is not the authentication support device;
• when the communication target device is determined not to be the authorized device, imposing a functional restriction on one or more functions of the communication target device which are operable by the control circuitry, wherein the functional restriction comprises permitting only an acquisition command for an operational state and setting information of the communication target device;
• when the communication target device is determined to be the authorized device, permitting, in addition to the acquisition command for the operational state and setting information, operation-related and setting-related commands of the communication target device, the operation-related and setting-related commands excluding acquisition of information on billing and privacy, and setting and changing of a driving operational state when the communication target device is determined to be the authorized device;
• and
• when the communication target device is determined not to be the authentication support device, performing communication in plain text with the communication target device with the functional restriction in the imposing.

A communication system including a control circuitry which performs encrypted communication with a device which has succeeded in mutual authentication using an electronic certificate,

• the control circuitry comprising:
• a determining unit which:
• determines whether or not a communication target device with which communication is to be performed is an authentication support device that supports the mutual authentication;
• and
• determines whether or not the communication target device is an authorized device when the communication target device is not the authentication support device;
• a functional restriction unit which:
• imposes a functional restriction on one or more functions of the communication target device when the communication target device is determined not to be the authorized device, wherein the functional restriction comprises permitting only an acquisition command for an operational state and setting information of the communication target device;
• and
• permits, in addition to the acquisition command for the operational state and setting information, operation-related and setting-related commands of the communication target device, the operation-related and setting-related commands excluding acquisition of information on billing and privacy, and setting and changing of a driving operational state when the communication target device is determined to be the authorized device;
• and
• a communication unit which:
• performs communication in plain text with the communication target device with the functional restriction imposed by the functional restriction unit when the communication target device is determined not to be the authentication support device.