You can remove all types of authentications by configuring the vnc server. As user start a vnc session and “-SecurityTypes none” option while starting a vnc server as below:
#vncserver :X -SecurityTypes None
In the above command, X is the display number at which the vnc session should start.
The “-SecurityTypes none” can be added to vnc service file by passing it to ExecStart = section. In this way, users do not need to enter this option every time while starting a vnc session with vncserver.
ExecStart=/usr/sbin/runuser -l startvnc -c "/usr/bin/vncserver %i -SecurityTypes None"