| 摘要 |
PROBLEM TO BE SOLVED: To provide a key management method and a key management system, that can continuously and efficiently add/delete subscribers. SOLUTION: Considering a dynamic tree structure B-tree with a root tree T, each subscriber ui corresponds to each leave 1i, a key KV is assigned to each vertex, v, each subscriber ui secretly has a set of keys corresponding to vertexes on a path from a corresponding leave 1i to a root R as the key of the subscriber ui, and since all the subscribers have a key KR corresponding to the root R in common, the key KR is used for a common key for contents distribution. In the case of adding/deleting a subscriber u, a leaf l corresponding to the subscriber u is added/deleted to/from a key management tree by the reconfiguration method of the B-tree to generate a new key management tree, keys corresponding to vertexes on a path from the added/deleted subscriber leaf 1 to the root R are newly generated, a message resulting from generated by encrypting the new key with a key corresponding to a slave of each apex on the path is broadcast to distribute the new key to subscribers belonging to partial trees of the slave of each vertex on the path.
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