INFORMATION EMBEDDING DEVICE, INFORMATION DETECTING DEVICE, INFORMATION EMBEDDING AND DETECTING SYSTEM, INFORMATION EMBEDDING METHOD, INFORMATION DETECTING METHOD, INFORMATION EMBEDDING PROGRAM, INFORMATION DETECTING PROGRAM, INFORMATION EMBEDDING AND DETECTING PRO

An information embedding device is provided that embeds information in a document image having a character region therein. This information embedding device includes: a character region detecting unit that detects the character region from the document image; a character region dividing unit that divides the character region into a plurality of sub regions; and a feature quantity increasing/decreasing unit that performs an operation to increase or decrease a feature quantity with respect to each of the sub regions to a value that is determined from a pseudorandom number sequence in accordance with predetermined rules.