Patent ID: 7346169
Filing Date: 2008-03-18
Classification: G06F,G11B,H04L

Abstract:
1. An information processing device operable within a node of a hierarchical network of nodes having a hierarchical tree structure, said information processing device comprising: storage operable to store one or more node keys, each node key being unique to one node of the network, and a leaf key, the leaf key being unique to the information processing device and unique in relation to a leaf key held by any other node within the hierarchical network of nodes; and an encryption processor operable to: decrypt an encrypted renewal node key of a key block to obtain a renewal node key using at least one of the node key stored in the storage or a leaf key belonging to a lower layer of the hierarchical network and stored in the storage, calculate a decryption key using the obtained renewal node key, encrypt the decryption key using the leaf key of the information processing device, store the encrypted decryption key in at least one of the storage or on a recording medium together with a generation number, the generation number representing renewal information for the decryption key, and use the generation number to determine whether it is necessary to decrypt a key block corresponding to the generation number to obtain the decryption key.