On the security cost of interval multicast

Interval multicast was defined as to send a message to a subset of a group, rather than all of the members in the group, which is important in battle fields and other applications. A key-tree based approach was proposed to achieve interval-multicast security, i.e., to securely multicast the message to the subgroup. The cost of the proposed approach is defined as the number of different keys needed to encrypt the message so that only the members within the subgroup can decrypt. In this paper, we propose another approach based on the subset difference scheme to achieve interval-multicast security. We formally prove that, given any subgroup, the cost of the subset-difference based approach is no bigger than the one of the key-tree based approach. Our experiment studies demonstrate that in most cases, the cost of the SD-based approach is much smaller.