Key management method used in encryption processing for safely transmitting and receiving messages

1. A key management method in a key management device serving as an electronic control unit (ECU) in an onboard network system having a plurality of electronic control units (ECUs) that perform communication by frames via a network, the method comprising:

storing, in a first-type electronic control unit out of the plurality of electronic control units, a shared key to be mutually shared with one or more second-type electronic control units other than the first-type electronic control unit, the shared key also being stored in the one or more second-type electronic control units other than the first-type electronic control unit;

executing encryption processing regarding a frame transmitted or received via the network, based on the shared key; and

executing, by the first-type electronic control unit, inspection of a security state of the shared key stored by the second-type electronic control units in a case where a vehicle in which the onboard network system is installed is in at least one particular state,

wherein the at least one particular state includes at least one of the following particular states,

(a) the vehicle is not driving and is an accessory-on state,

(b) a fuel cap of the vehicle is open, and the vehicle is not driving and is fueling,

(c) the vehicle is parked, which is indicated by the gearshift,

(d) the vehicle is in a stopped state before driving, which is indicated by the gearshift, and

(e) a charging plug is connected to the vehicle, and the vehicle is electrically charging.

2. The key management method according to claim 1 ,

wherein the inspection is an inspection relating to an expiration date of the shared key.

3. The key management method according to claim 1 ,

wherein the inspection is an inspection relating to a serial ID of the second-type electronic control unit that stores the shared key.

4. The key management method according to claim 1 ,

wherein, in a case where the plurality of electronic control units includes a plurality of the second-type electronic control units, the inspection is an inspection relating to a transmission order of frames at the plurality of second-type electronic control units.

5. The key management method according to claim 4 ,

wherein the first-type electronic control unit transmits a frame indicating a predetermined request and thereafter sequentially receives frames from the plurality of second-type electronic control units, and based on the IDs of the frames, performs the inspection by distinguishing whether or not the IDs have been received in an order that a predetermined order list indicates.

6. The key management method according to claim 1 ,

wherein the first-type electronic control unit executes the inspection only in a case of the particular state.

7. The key management method according to claim 1 ,

wherein the first-type electronic control unit executes the inspection by communication with a server located externally from the vehicle.

8. The key management method according to claim 1 ,

wherein the plurality of electronic control units perform communication by frames via the network, following a Controller Area Network protocol.

9. An onboard network system having a plurality of electronic control units (ECUs) that perform communication by frames via a network, the system comprising:

a first-type electronic control unit, out of the plurality of electronic control units, configured to store a shared key to be mutually shared with one or more second-type electronic control units other than the first-type electronic control unit, the shared key also being stored in the one or more second-type electronic control units other than the first-type electronic control unit; and

each of the second-type electronic control units configured to execute encryption processing regarding a frame transmitted or received via the network, based on the shared key,

wherein the first-type electronic control unit executes inspection of a security state of the shared key stored by the second-type electronic control units in a case where a vehicle in which itself is installed is in at least one particular state,

(a) the vehicle is not driving and is an accessory-on state,

(b) a fuel cap of the vehicle is open, and the vehicle is not driving and is fueling,

(c) the vehicle is parked, which is indicated by the gearshift,

(d) the vehicle is in a stopped state before driving, which is indicated by the gearshift, and

(e) a charging plug is connected to the vehicle, and the vehicle is electrically charging.

10. A key management device serving as an electronic control unit (ECU) in an onboard network system having a plurality of electronic control units (ECUs) that perform communication by frames via a network, the device comprising:

a processor; and

a memory having a computer program stored thereon, the computer program causing the processor to execute operations including

storing a shared key to be mutually shared with one or more electronic control units other than itself out of the plurality of electronic control units, the shared key also being stored in the one or more second-type electronic control units other than the first-type electronic control unit, and

inspecting of a security state of the shared key stored by the electronic control units other than itself in a case where a vehicle in which itself is installed is in at least one particular state,

(a) the vehicle is not driving and is an accessory-on state,

(b) a fuel cap of the vehicle is open, and the vehicle is not driving and is fueling,

(c) the vehicle is parked, which is indicated by the gearshift,

(d) the vehicle is in a stopped state before driving, which is indicated by the gearshift, and

(e) a charging plug is connected to the vehicle, and the vehicle is electrically charging.