Session Announcement Protocol

In the session announcement protocols described in Chapter Seven, announcements that are multicasted out can include a session key for each media stream. Obviously, the announcement packets must themselves be encrypted. It is intended that the receivers will be supplied with a set of keys which are used to receive session announcements. When an encrypted announcement is received, the receiver will go through the set of keys trying to decrypt the message using each of its keys. If it succeeds, then the announcement is displayed and cached, or else it is discarded, and only the id of the announcement is retained to discard duplicates.