A camera generates a random number, displays a Quick Response (QR) code representing the generated random number, and transmits the generated random number to a web server. A smart phone captures an image of the QR code displayed on the camera, acquires the random number based on the captured QR code, and transmits the acquired random number to the web server. The web server registers the camera based on a match between the random number transmitted from the camera and the random number transmitted from the smart phone.