| 摘要 |
PROBLEM TO BE SOLVED: To provide an image data encryption technique which facilitates management of access keys in encrypting image data having a hierarchical structure in which the data of each layer can be specified by at least two parameters, and is also resistant against exchange of access keys between a plurality of users. SOLUTION: In encrypting image data having a hierarchical structure in which a layer is specified by layer and resolution level, an access key K for the highest resolution and highest layer is set. Access keys are generated by using a one-way function in a direction which the level becomes low. At such a time, the access key for a given layer can be generated from either of the access keys of layer and resolution located at the higher level. The data of each layer are encrypted in accordance with a corresponding access key. COPYRIGHT: (C)2007,JPO&INPIT
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