Key managing method of home device in be system and system thereof

A method and a system of managing a key of a home device in a broadcast encryption system is provided to reduce a transmission overhead of a header of a service provider when the home device belonging to the home server is incorporated into or eliminated from a service. A method for managing a key of a service provider(290) is applied in a system including the service provider, a home server(260), and a home device(230). A hierarchical structure of a group set comprising a plurality of nodes corresponding to a home server and a plurality of nodes corresponding to a home device is formed(S200). A key set to be allotted to the node set is generated(S205). The node group corresponds to the key set to generate key-node corresponding information according to a request of the home server.