These are the self-signed certificates which you are stored within the Local 
Hosts resources.
So if you see such messages like "An authentication request from <client> was 
denied. ..." in the daemon.raw file, you should take appropriate action and 
delete them on all peers.

+----------------------------------------------------------------------
|This was sent by carsten_reinfeld AT avus-cr DOT de via Backup Central.
|Forward SPAM to abuse AT backupcentral DOT com.
+----------------------------------------------------------------------