Tampering judgement system, encrypting system for judgement of tampering and tampering judgement method

Abstract

A tampering judgement system is provided which is capable of easily checking whether or not a printed document has been tampered. An image feature information extracting section extracts image feature information from a document image. An image feature information embedding section gives image feature information integrally as original image feature information to a document and a document image output section outputs the information as a printed document. When the printed document is given to the tampering judgement system, the image data is read by a document image reading section. An image feature information extracting section extracts image feature information contained in a document being an object for judgement on tampering. An embedding information extracting section extracts original image feature information from image data. A judging section compares original feature information with image feature information contained in the printed document and if a difference between them exceeds a predetermined threshold value, the document is judged to have been tampered.