Wireless communications device and authentication processing method

A wireless communications device which performs an authentication process at a self-driven vehicle that performs wireless communications with another vehicle or a fixed station, said wireless communications device comprising:

• a central processing unit;
• a memory coupled to the central processing unit;
• and
• an input/output interface coupled to the central processing unit;
• wherein the memory stores instructions that, when executed by the central processing unit, cause the central processing unit to perform a first process and a second process,
• wherein the first process includes generating a message authentication code of communication data using a common key shared between the self-driven vehicle and the other vehicle or the fixed station, generating a digital signature using a secret key inherent in the self-driven vehicle itself, generating position information of the self-vehicle, and transmitting the communication data with each of the generated message authentication code, the generated digital signature, and the position information of the self-vehicle added thereto via the input/output interface,
• wherein the second process includes receiving information transmitted from the other vehicle or the fixed station via the input/output interface including position information of the other vehicle or the fixed station, and determining whether authentication is to be performed with one or more of a message authentication code and a digital signature which are both included in the received information,
• wherein the second process includes generating an authentication required value by executing an authentication request generating function according to a load state of the central processing unit and a distance of the self-vehicle from the other vehicle or the fixed station based on the position information of the other vehicle or the fixed station,
• wherein the authentication required value indicates whether a first authentication process using the received digital signature is to be executed for the received information, and whether a second authentication process using the received message authentication code is to be executed for the received information,
• wherein the load state is one of a first load state, a second load state indicating that a load of the central processing unit is heavier than that of the first load state, and a third load state indicating that the load of the central processing unit is heavier than that of the second load state,
• wherein the central processing unit generates, when the central processing unit is in the first load state, the authentication required value to indicate the first authentication process and the second authentication process are both to be executed,
• wherein the central processing unit generates, when the central processing unit is in the second load state and the distance is less than a first value and less than a second value, the authentication required value to indicate the first authentication process is to be executed and the second authentication process is not to be executed,
• wherein the central processing unit generates, when the central processing unit is in the second load state and the distance is greater than the first value and less than the second value, the authentication required value to indicate the first authentication process is not to be executed and the second authentication process is to be executed,
• wherein the central processing unit generates, when the central processing unit is in the second load state and the distance is greater than the first value and greater than the second value, the authentication required value to indicate the first authentication process and the second authentication process are both not to be executed, and
• wherein the central processing unit checks, when the central processing unit is in the third load state, whether a vehicle ID of the received information has been cached in the memory, and
• the central processing unit generates the authentication required value to indicate the first authentication process is not to be executed and the second authentication process is to be executed when the vehicle ID is not cached in the memory, and to indicate the first authentication process and the second authentication process are both not to be executed when the vehicle ID is cached in the memory, and
• wherein the central processing unit executes the first authentication process and the second authentication process as indicated by the authentication required value.