Patent ID: 8081754
Filing Date: 2011-12-20
Classification: H04L,H04W

Abstract:
1. A key update method for a member that has switched from an offline mode to an online mode, the method comprising: storing, by an update server, data in a database of an update server, the data having an encoded updated node key in response to a node key update for a group; selecting, by the update server, necessary data, from among the data having the encoded updated node key, to calculate a key immediately prior to when the member is switched to the online mode, and generating member update data; and providing the member update data to a device corresponding to the member which has switched from the offline mode to the online mode, wherein, the member update data is used in performing a key update with respect to the member, and when a node joins the group, the data having the encoded updated node key is generated by encoding an ancestor node key other than a root node key, corresponding to the ancestor node of the node that joins the group, into a child node key.