<a href="http://www.cs.georgetown.edu/~clay/">Clay Shields</a>, "KHIP - A Scalable Protocol for Secure Multicast Routing"

Multicast routing is a service that provides for efficient
many-to-many communication in a network. Traditionally, secure
multicast protocols have used existing multicast routing services
and relied on cryptographic protection of the messages sent to
provide security. Much previous work in the area has been on
methods of establishing a shared key between members subscribing to
the multicast group. Some problems with this approach are that any
network member can receive the encrypted traffic, and that the
multicast routing protocol itself is subject to attacks which allow
for effective denial-of-service attacks against the group members.
I present Keyed-HIP (KHIP), a protocol for secure, hierarchical,
multicast routing that changes the multicast model to prevent
non-group members from receiving the secure traffic, and limits the
effectiveness of denial of service attacks against the multicast
group. KHIP also provides an efficient mechanism for distributing
data encryption keys to all members of the group. While the type of
security provided by KHIP is not necessary in all cases, for some
applications the traditional model of multicast security may be
lacking.