Network security (security in large networks)

It is common that users or hosts in a large network are partitioned and organized as a hierarchical free where children of the same parent from a group. Secure broadcasting intends to provide a secure communication channel from a sending principal to a group of legal receiving principals. Only legal receiving principals can decrypt the message, and illegal receiving principals cannot acquire any information from the broadcasted message. We propose a secure broadcasting protocol in which only one packet is transmitted for every broadcast and the size of the broadcasted packet is small.