A SECURE BROADCAST COMMUNICATION METHOD WITH SHORT MESSAGES

Broadcasting with secrecy of messages is important in a situation such as pay television. In pay television only a broadcasting station broa dcasts a message. On the other hand, broadcast communication is also i mportant. Broadcast communication means any user in a whole group can broadcast a message to any subset of the group. In this paper the effi ciency of secure broadcast communication is discussed in terms of the length of messages sent and the encryption speed. We prove that the le ngth of the broadcast messages is not kept less than O (n), where n is the number of receivers, when a broadcast system has a form of a sing le system which is defined as the generalized form of an individual ke y method and a master key method. In contrast, the proposed secure bro adcast communication method, a multi-dimension method, keeps the lengt h of messages sent [GRAPHICS] where m is the number of the dimension u sed in the multi-dimension method. At the same time the encryption spe ed was reduced from O (n(log(n + C2) + C3)) of the master key method t o [GRAPHICS] of the multi-dimension method.