-two SILC clients. In normal case, where client is connecting to the
-server, or server is connecting to the router the Mutual Authentication
-flag is not necessary.
+two SILC clients. In normal case, where client is connecting to a
+server, or server is connecting to a router the Mutual Authentication
+flag may be omitted. However, if the connection authentication protocol
+for the connecting entity is not based on public key authentication (it
+is based on passphrase) then it is RECOMMENDED that Mutual Authentication
+flag is enabled. This way the connecting entity has to provide proof
+of posession of the private key for the public key it will provide in
+SILC Key Exchange protocol.