An information processing system and method are disclosed in which information processing is performed using an enabling key block (EKB) in association with a tree structure including category subtrees. A key tree is produced, which include subtrees that are grouped in accordance with categories and are managed by category entities. The EKB includes data produced by selecting a path in the key tree and encrypting a higher-level key in the selected path using a lower-level key in the selected path. The EKB is then provided to a device. A requester, which requests production of the EKB, may produce a root key or may request a key distribution center (KDC) to produce a root key. If the (KDC) produces the EKB, it may also request a category entity to produce a sub-EKB.