US Patent 7627755 Secure broadcast/multicast service

A method of authenticating candidate members 1 wishing to participate in an IP multicast via a communication network, where data sent as part of the multicast is to be encrypted using a Logical Key Hierarchy based scheme requiring that each candidate member submit a public key to a group controller. The method comprises, at the group controller 1, verifying that the public key received from each candidate member 1 is owned by that member and that it is associated with the IP address of that candidate member 1 by inspecting an interface ID part of the IP address.