Information processing system and method

An information processing method for distributing an enabling key block (EKB) requested by an EKB requester, wherein the EKB includes an encrypted key set formed by encrypting an upper-level node key in a selected path in a category tree by a lower-level node key in the selected path in the category tree, the category tree being a part of a key tree and being grouped in accordance with a category managed by a category entity, and wherein the key tree includes leaves, a root, and nodes existing in paths from each of the leaves to the root, each of the leaves being assigned to a device, the information processing method comprising:

• receiving EKB requests requesting an EKB by an EKB type identifier from the EKB requester;
• identifying one or more category trees from an EKB type definition list defining the EKB type identifier and identifying one or more category tree identification data to match the EKB specified by the EKB type identifier received from the EKB requester;
• creating an EKB to be decrypted in common in the one or more category trees identified by the identifying means;
• and
• distributing the EKB created by the creating means to the EKB requester.

An information processing apparatus for distributing an enabling key block (EKB) requested by an EKB requester, wherein the EKB includes an encrypted key set formed by encrypting an upper-level node key in a selected path in a category tree by a lower-level node key in the selected path in the category tree, the category tree being a part of a key tree and being grouped in accordance with a category managed by a category entity, and wherein the key tree includes leaves, a root, and nodes existing in paths from each of the leaves to the root, each of the leaves being assigned to a device, the information processing apparatus comprising:

• a receiver configured to receive EKB requests requesting an EKB by an EKB type identifier from the EKB requester;
• an identifier module configured to identify one or more category trees from an EKB type definition list defining the EKB type identifier and identifying one or more category tree identification data to match the EKB specified by the EKB type identifier received from the EKB requester;
• a creator module configured to create an EKB to be decrypted in common in the one or more category trees identified by the identifier module;
• and
• a distributor module configured to distribute the EKB created by the creator module to the EKB requester.

A program storage medium having a computer program for enabling a key distribution apparatus to distribute an enabling key block (EKB) requested by a EKB requester, wherein the EKB includes an encrypted key set formed by encrypting an upper-level node key in a selected path in a category tree by a lower-level node key in the selected path in the category tree, the category tree being a part of a key tree and being grouped in accordance with a category managed by a category entity, and wherein the key tree includes leaves, a root, and nodes existing in paths from each of the leaves to the root, each of the leaves being assigned to a device, the program comprising instructions to cause the key distribution apparatus to:

• receive EKB requests requesting an EKB by an EKB type identifier from the EKB requester;
• identify one or more category trees from an EKB type definition list defining the EKB type identifier and identifying one or more category tree identification data to match the EKB specified by the EKB type identifier received;
• create an EKB to be decrypted in common in the one or more category trees identified;
• and
• distribute the EKB created to the EKB requester.