JUSTIFICATION AUTHENTICATING SYSTEM, PERSONAL CERTIFICATE ISSUING SYSTEM, AND PERSONAL CERTIFICATE

A justification/authentication personal certificate system stores in a remote database a counterpart of an identifier and a digital watermark contained in the personal certificate. The personal certificate includes the digital watermark embedded in an authentic image such as a facial photograph, a retinal scan, or a fingerprint. When the personal certificate is used, the authentic image is read from the personal certificate, and the digital watermark information is extracted. The digital watermark information and the identifier are compared with the counterparts stored in the database. If the extracted digital watermark information is identical to the information in the database, then the personal certificate is judged to be unjustifiable. In one embodiment, at least one of the identifier and digital watermark are changed each time the system justifies the personal certificate.