Method of managing a key of user for broadcast encryption

The administrative user key for a broadcast encryption method is disclosed. The present invention is to impart a node path ID (Node Path ID) to each node are arranged in order, to impart a random seed key (Seed Value Key) according to a node path ID of each node, the provided random seed the steps, and the generated key value to generate a key value by applying a hash function to the key repeatedly for each node is achieved through the step of imparting sequentially. According to the present invention, it is possible in the broadcast encryption to reduce the most important transmission rate to less than r. Further, in the embodiments of the present invention it has the advantage that the transmission amount is not significantly reduced as compared to the SD known the best method to date. A broadcast encryption, the hash function, the seed key, the hash chain, the hierarchy