Patent ID: 8205085
Filing Date: 2012-06-19
Classification: H04L

Abstract:
1. A key update system for a multihop network system comprising a key management device that manages keys, and a plurality of communication terminals that obtain the keys, wherein the multihop network has a hierarchical structure in which the communication terminals communicate with the key management device via a tree arrangement in which a first one of the communication terminals at a first hop from the key management device is a first parent terminal, a second one of the communication terminals at a second hop from the key management device is a second parent terminal that communicates with the first parent terminal, the second parent terminal and all other communication terminals at the second hop that communicate with the first parent terminal form a first group having a first common group key, and all communication terminals at a third hop from the key management device that communicate with the second parent terminal form a second group having a second common group key, wherein the hierarchical structure of the multihop network is such that at least one of the first and second groups includes three or more communication terminals, wherein the key management device comprises: wherein each of the communication terminals comprises: