INFORMATION PROCESSING EQUIPMENT AND PROGRAM

摘要

In realizing a secure multicast transmission to a plurality of terminal devices, a disturbing portion (212) rearranges ID's of the terminal devices connected to a server device (201) and generates various kinds of orderings of the terminal devices. Then, a structure information generating portion (219) generates structure information on a plurality of tree structures which correspond to the various kinds of orderings, respectively, and a key assignment portion (213) assigns secret information to each node of each tree structure. A set determining portion (216) determines such structure information that only the terminal devices which are the destination of the secure multicast are assigned secret information which allows for decoding of an encoded message and there is the least communication overhead. An encoding portion (218) encodes a message to be transmitted using the secret information assigned to the structure information determined by the set determining portion (216), and a communicating portion (217) multicast-transmits the encoded message.