| 摘要 |
<p>Sub-trees separated according to the data processing capability of a device are defined in a key tree in which keys are assigned to the roots, nodes, and leaves which are devices of a tree. A management entity of each sub-tree creates a sub make-effective key block effective in the entity. A key issuing center creates a make-effective key block decodable only by an entity having common capability according to the capability information on the entity. Each entity manages the partia trees (sub-trees) of the key tree, creates a sub make-effective key block according to only the nodes of the sub-trees or the keys corresponding to the leaves, and creates a make-effective key block decodable only by the selected entity by using the sub make-effective key block. Thus, a make-effective key block can be created in accordance with the data processing capability of a device and distributed, and the key tree hierarchical structure can be dividedly managed.</p> |
