Group Key Update method and apparatus using the same group key update

The group key update methods and apparatus for binary tree (binary tree) (multi leave) a group corresponding to the multi-withdrawal is disclosed. Group key update method according to an embodiment of the present invention comprises the steps of selecting a sub-root node of the node in the binary tree; Further comprising: according to the type of the sub-root node to the node performing the change (change node) for the group generate a transformed binary tree; And characterized by including the step of performing a key update with respect to the node changes the binary tree. Therefore, it is possible to efficiently perform group key updates to the multi-withdrawal. Group key, key updates, one-way function, the batch