Patent ID: 7774605

Claim:
An apparatus, which provides a public-key cryptography digital signature for an image data, said apparatus comprising: a storage unit configured to store a private key of the apparatus; a signature calculating unit configured to calculate an apparatus public-key cryptography digital signature from a portion of image appurtenant information including a part of a characteristic quantity of the image data using the private key of the apparatus; a signature adding unit configured to add the apparatus public-key cryptography digital signature to the image appurtenant information in the image-data format; and a data handling unit configured to calculate a characteristic quantity of the image appurtenant information including the characteristic quantity of the image, configured to store the characteristic quantity as the image appurtenant information in the image data format, configured to calculate a user digital signature from said calculated characteristic quantity using a private key of a user of the apparatus, which is stored in an external storing unit loaded in said apparatus, and configured to store the user digital signature and the apparatus digital signature as the image appurtenant information in the image-data format.