NOT provide the signature data. If the flag is set then the initiator
MUST provide the signature data so that the responder can verify it.
-The Mutual Authentication flag is usually used only if a separate
+The Mutual Authentication flag is usually used when a separate
authentication protocol will not be executed for the initiator of the
protocol. This is case for example when the SKE is performed between
-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.
When performing re-key with PFS selected this is the only payload that
is sent in the SKE protocol. The Key Exchange Start Payload MUST NOT