| 摘要 |
<p>A user key storage unit stores at least one user key corresponding to usage authorities of image data. A first encryption unit encrypts the image data using a first encryption key. A second encryption key creation unit creates a second encryption key assigned to each usage authority. A key-storage data creation unit creates a key-storage data for each usage authority by encrypting the first encryption key and authority information using the second encryption key. A user-supplementary data creation unit creates user-supplementary data (an identifier of the user key and the second encryption key encrypted using the user key) for each user key. A device-supplementary data creation unit creates device-supplementary data (an identifier of the device key and the second encryption key encrypted using the device key) for at least one usage authority and for at least one device key. A data output unit outputs encrypted image data with the key-storage data, the user-supplementary data and the device-supplementary data.</p> |
