1. Field of the Invention
The present invention relates to an image printing device that prints an image, and more particularly to an image printing device, a verifying device, and printed material that enable to prevent falsification of a certificate.
2. Description of the Related Art
Various methods have been know for preventing falsification and unauthorized use of a certificate (for example, employee identification etc.). In one method, an identification code is printed on an ID card in the form of a bar code or a Quick Response (QR) code, and the identification code is also maintained at a control server. When performing verification of the ID card, the identification code printed on the ID card is read and transmitted to the control server. If the read identification code is maintained in the control server, it is determined that the ID card is authentic.
In another method, a photograph of the face of the possessor of an ID card is printed on the ID card. When a person presents an ID card, it is determined from the photograph printed on the ID card whether the person is an authentic possessor of the ID card. Integrated Circuit (IC) ID cards that carry a photograph of the face of the possessor of the card printed thereon have appeared in market. When a person presents such an IC ID-card, it is determined whether that person is an authentic possessor of the IC-ID card based on the photograph printed on the IC-ID card and data recorded in the IC ID-card.
Japanese Patent Laid-Open Publication No 2001-94755 discloses invisibly embedding security data in a background portion of a main image (a facial image of the user etc.), thereby enabling to determine whether the certificate is authentic. When embedding data, first the background portion and other portion of an original image are separated, then the security data is embedded into the background portion, and finally the security data embedded background portion and the other portion are combined to obtain an image for printing on an IC ID-card. This process prevents deterioration of the image due to embedding of the security data.
However, the conventional methods are not very reliable; because, the bar code printed on the certificate can be easily falsified or the facial photograph affixed to the certificate can be easily replaced, whether the certificate is authentic cannot be determined accurately.
When determining whether the certificate is authentic for a certificate that does not include a facial photograph specifying the user, the verifying device determines whether the certificate is authentic by using only the bar code or the QR code that is printed on the certificate. The bar code or the QR code is a standardized code and can be easily falsified by an unauthorized user.
When determining whether the certificate is authentic for the IC card certificate with a photograph, an unauthorized user can illegally get hold of the IC card certificate with the photograph and replace the photograph on the IC card certificate with his or her own photograph. Thus, the unauthorized user can easily pass off as the IC card certificate holder.
In the technology disclosed in Japanese Patent Laid-Open Publication No 2001-94755, because the security data is embedded only in the background portion of an image, the image processing device cannot determine whether a falsification such as cutting part of other portion, which is the main portion in the image, has been carried out.
There is a need of a realibale and easy technique to prevent falsification of ID cards.