In this paper we propose a dual encryption protocol for scalable secure multicasting. Multicasting is a scalable solution for group communication. It however, poses several unique security problems. We use hierarchical subgrouping to achieve scalability. Third party hosts or members of the multicast group are designated as subgroup managers. They are responsible for secret key distribution and group membership management at the subgroup level. Unlike existing secure multicast protocols, our protocol need not trust the subgroup managers with the distribution of data encryption keys. The dual encryption protocol proposed in this paper distributes encrypted data encryption keys via subgroup managers. We also present a classification of the existing secure multicast protocols, compare their relative merits and show the advantages of our protocol.