Reuse system, key generation device, data security device, in-vehicle computer, reuse method, and computer program

A reuse method of an in-vehicle computer that is detached from a first vehicle and is installed in a second vehicle, the reuse method comprising:

• generating, by a server device that is provided outside a vehicle and executes processing related to a reuse of a used in-vehicle computer, a root key that is the same as a key stored in the in-vehicle computer from a time when the in-vehicle computer was installed in the first vehicle by using an in-vehicle computer identifier of the in-vehicle computer and a master key that is common to the first vehicle and the second vehicle;
• transmitting, by the server device, the root key to the second vehicle through a vehicle interface that transmits and receives data to and from the second vehicle;
• encrypting, by a data security device, an in-vehicle key, which is applied to the in-vehicle computer, with the root key received from the server device through a first interface that transmits and receives data to and from an external device of the data security device to generate an encrypted in-vehicle key;
• transmitting, by the data security device, the encrypted in-vehicle key to the in-vehicle computer through the first interface;
• decrypting, by the in-vehicle computer, the encrypted in-vehicle key, which is received from the data security device through a second interface that transmits and receives data to and from an external device of the in-vehicle computer, with the root key stored in a second storage unit of the in-vehicle computer from a time when the in-vehicle computer was installed in the first vehicle;
• performing, by the in-vehicle computer, measurement of data that is applied to the in- vehicle computer by using a signature key that is stored in the in-vehicle computer;
• generating, by the server device, the signature key that is the same as a key stored in the in-vehicle computer from the time when the in-vehicle computer was installed in the first vehicle by using the in-vehicle computer identifier and the master key;
• calculating, by the server device, an expected value of the measurement by using the generated signature key;
• and
• verifying a measurement result which is received from the in-vehicle computer, with the expected value,
• wherein the server device includes a data storage configured to store data already applied to the in-vehicle computer at a time when the in-vehicle computer is installed in the second vehicle, and
• wherein in the calculating of the expected value, the expected value of the measurement for the data is calculated, the data being stored in the data storage and already applied to the in-vehicle computer at the time when the in-vehicle computer, which is detached from the first vehicle and is installed in the second vehicle, is installed in the second vehicle.

A non-transitory computer-readable recording medium storing a computer program that causes a computer of a key generation device, which is provided outside a vehicle and executes processing related to a reuse of a used in-vehicle computer and includes a vehicle interface that transmits and receives data to and from a second vehicle on which an in- vehicle computer detached from a first vehicle is installed, to realize processing of:

• generating a root key that is the same as a key stored in the in-vehicle computer from a time when the in-vehicle computer was installed in the first vehicle by using an in-vehicle computer identifier of the in-vehicle computer, and a master key that is common to the first vehicle and the second vehicle;
• transmitting the root key to the second vehicle through the vehicle interface;
• generating a signature key that is the same as a key stored in the in-vehicle computer from the time when the in-vehicle computer was installed in the first vehicle by using the in-vehicle computer identifier and the master key;
• and
• calculating an expected value of the measurement for data applied to the in-vehicle computer by using the signature key that is generated,
• wherein the server device includes a data storage configured to store the data already applied to the in-vehicle computer at a time when the in-vehicle computer is installed in the second vehicle,
• wherein in the calculating of the expected value, the expected value of the measurement for the data is calculated, the data being stored in the data storage and already applied to the in-vehicle computer at the time when the in-vehicle computer, which is detached from the first vehicle and is installed in the second vehicle, is installed in the second vehicle, and
• wherein the measurement result, which is transmitted from the in-vehicle computer, is verified with the expected value.