MULTICAST COMMUNICATING SYSTEM, GROUP KEY GENERATION METHOD, AND TERMINAL DEVICE

摘要

PROBLEM TO BE SOLVED: To provide a group key management system which is capable of switching a plurality of group keys for a group and performing secure and efficient group key management. SOLUTION: A group key generation method includes steps of: generating leaf node secret keys per terminal device; generating leaf node camouflage keys of terminal devices from the leaf node secret keys of the terminal devices; generating nCr kinds of secret keys of an intermediate node being a parent node by using leaf node camouflage keys of (n) terminal devices belonging to one sub-group; generating nCr kinds of secret keys of a higher-order node by using the same kind of camouflage keys out of nCr kinds of intermediate node camouflage keys of the intermediate node and nCr kinds of camouflage keys of two other intermediate nodes being brother nodes of the intermediate node (wherein (n) and (r) are positive integers and satisfy n>r≥2). COPYRIGHT: (C)2009,JPO&INPIT