A partial data acquisition unit acquires partial data included in digital data, a partial data specifying information acquisition unit acquires specifying information for the partial data, a combining unit combines the partial data and the specifying information, and a verification data generation unit generates verification data. Thus, it is possible to verify whether or not region data in image data has been altered. In addition, it is possible to verify that the region data is the region data in image data different from the original image data, and/or, it is possible to further verify that the region data is the different region data included in the original image data.