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Key management system and playback apparatus

  • US 20050271211A1
  • Filed: 05/18/2005
  • Published: 12/08/2005
  • Est. Priority Date: 05/18/2004
  • Status: Abandoned Application
First Claim
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1. A key management apparatus for generating key information in association with a tree structure which has at least one root node and in which plural nodes are assigned under a node as leaves, comprising;

  • a composite number operating unit which calculates a composite number which is a product of more than one arbitrary prime numbers;

    a first confidential information storage unit which stores an arbitrary natural number which is smaller than the composite number and is relatively prime to the composite number, as first confidential information, in association with the root node;

    a public information storage unit which stores natural numbers, which are relatively prime to each other in a subset expressed by a combination of plural child nodes of an arbitrary node in the tree structure, as public information in association with the subset;

    a first master key operating unit which calculates master keys corresponding to the child nodes of the root node based on the first confidential information assigned to the root node and the public information;

    a first master key storage unit which stores the master keys in association with the corresponding child nodes;

    a second confidential information operating unit which calculates, for each node, second confidential information, by a bijective function based on the master keys set to parent node having the node as the child node and the composite number;

    a second confidential information storage unit which stores the second confidential information in association with the corresponding arbitrary node;

    a second master key operating unit which calculates the master keys corresponding to the child nodes of each of the nodes based on the second confidential information assigned to each of the nodes and the public information;

    a second master key storage unit which stores the master keys in association with the corresponding child nodes;

    an encryption/decryption key operating unit which calculates encryption/decryption keys, for the subset, based on the first confidential information or the second confidential information assigned to the node and the public information; and

    an encryption/decryption key storage unit which stores the encryption/decryption keys in association with the nodes.

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