Patent ID: 7405731

Claim:
An information processing system 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: receiving means for receiving EKB requests requesting an EKB by an EKB type identifier from the EKB requester; identifying means for 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 means for creating an EKB to be decrypted in common in the one or more category trees identified by the identifying means; and distributing means for distributing the EKB created by the creating means to the EKB requester.