A system classifies an image file into a first group if authentication data included in the image file has been generated using a private key cryptosystem, and classifies the image file into a second group if the authentication data included in the image file has been generated using a public key cryptosystem. The system authenticates whether or not image data included in the image file has been altered using the authentication data. The system displays an indication of whether or not the image data included in the image file has been altered in a display area corresponding to the first group, if the image file is classified in the first group. The system displays an indication of whether or not the image data included in the image file has been altered in a display area corresponding to the second group, if the image file is classified in the second group.