| 摘要 |
<p>The present invention is a data protection system that includes a multiplicity of terminals, and an encryption device that encrypts distribution data that is distributed to each terminal. Each terminal is corresponded with one node on a lowest level of 4-ary tree structure or the like that has a plurality of hierarchies. The data protection system, for each node in the tree structure, excluding those on the lowest level, determines a plurality of combination patterns that include combinations of two or more of all four nodes that are reached one level below the node, decides an individual decryption key for each determined combination pattern, further decides an individual decryption key for each node on the lowest level, and has each terminal store all decryption keys decided for the nodes on the path from the node on the lowest level that corresponds to the terminal through to the node on the highest level.</p> |
