Method of managing a key of user for broadcast encryption

摘要

A method of managing a key of a user for a broadcast encryption. The method includes forming a tree comprising m hierarchies by repeating a process of setting a i^th level comprising groups into which at least one node is grouped in a unit of n_i, and setting a i+1^th level comprising the groups of the i^th level that are re-grouped in a unit of n_i+l until i is from "1" to "m". The method further includes mapping users on at least one node of the tree and message providers on the m^th hierarchy, going down from the m^th hierarchy to the first hierarchy to map key encryption keys with respect to the i+1 ^th level connected to the i^th level, and transmitting the message using the key encryption keys.