Patent ID: 8855306

Claim:
A node that is a root node of a network forming a directed acyclic graph topology by plural nodes, the plural nodes including the node serving as the root node and having a parent-child relationship among nodes of adjacent hierarchies, the node comprising: a generating unit, implemented by processing circuitry, that generates a group key and a list indicating a specific node to which a distribution of the group key is inhibited; an encrypting unit that encrypts the group key to obtain an encrypted group key; and a transmitting unit that transmits, to the first child node, a first message including the encrypted group key and the list, wherein the encrypted group key is decryptable by a first child node of the root node, the first child node being a node other than the specific node, wherein the encrypting unit encrypts the group key using a shared key shared only between the root node and the first child node, and wherein after receipt of the first message including the encrypted group key and the list by the first child node, the list is accessed by the first child node in order to identify any nodes for which distribution of the group key is inhibited.