A system includes circuitry configured to embed a digital watermark data in an original image, wherein the original image is divided into a plurality of blocks each block having been embedded with a pattern corresponding to each value of the digital watermark data, store, in a memory, the original image, the digital watermark data embedded in the original image, and an embedding position of the pattern of the digital watermark data in association, detect a pattern in a scanned image of a printed matter, decode the detected pattern to acquire digital watermark data included in the scanned image, align each block between the original image and the scanned image, based on the embedding position of the pattern associated with the original image and a detection position of the pattern detected from the scanned image, and obtain a difference between the original image and the scanned image aligned with each other.