Method for key generation to reduce transmission overhead in broadcast encryption, encryption and decryption using the key generation

The key generation method used in broadcast cryptography is disclosed. At least one node to the key generation method, and assigns a plurality of nodes to each of a plurality of rows, configuring any one of a line among the plurality of rows includes at least one of the nodes of the other one of the row from the plurality of rows forming a hierarchical group of nodes including a plurality of nodes to be associated with each other; Allocating at least one of the node key to each of all the nodes forming the hierarchical group of nodes; Allocating at least one one-way function for each of the plurality of rows; Two nodes that are assigned to at least one line at least one one-way function, each with a set interval consisting of two nodes selected from all the nodes forming the hierarchical group of nodes, and form the interval applied to generating a segment key of the segment, and assigned to any one of the nodes the created segment key from the selected two nodes: and the user to each of the plurality of nodes of the final line from among the plurality of rows a comprises the step of assigning. The key generation method can reduce the transmission rate of the broadcast encryption. Broadcast encryption, throughput