Method for managing group key for secure multicast communication

A method for managing group key for multicast communications is provided to reduce a use cost of network by minimizing the number of message transmitted to network for key renewals. A method for managing group key for multicast communications comprises the following steps: a step for producing a tree which is comprised to a root, an in-between, and a leaf node for a group key management of a receiver group in a management server(S100); a step for producing a user key about each node except for a root node using a chinese remainder theorem(S110); a step for assigning each user belonging to the receiver group to the leaf node(S120); a step for delivering the user key for the group key management of the corresponding leaf node to each user(S130); a step for producing the group key about each node except for the leaf node(S140); a step for calculating the chinese remainder theorem value using the user key and the group key in each node except for the leaf node(S150); and a step for transmitting a group key update message to a multicast(S160).