To provide an authentication technique having higher security between IoT devices and server devices or between IoT devices.
The server device provides, to the terminal device, a parameter file including a predetermined identifier for uniquely identifying a relationship between the terminal device and the server device, and connection destination information regarding a connection destination of the server device, the terminal device accesses the server device specified by the connection destination information in the parameter file, requests issuance of a timed identification number, and transmits the identifier and the timed identification number to the server device when connecting to the server device specified by the connection destination information in the parameter file, and the server device authenticates the terminal device using the identifier, and confirms an authenticity of the terminal device using the timed identification number.