I have tried several ways to set this using dconf-edit, gsettings and such
as well as directly editing the files this is stored in.  I still get the
"you need to upgrade your viewer to higher level security" error on Windows
machines.  I wish to set "require-encryption" to false rather than default
of true.

In the console print out I see the security level 18 is being offered and
many viewers (mostly windows) do not know what this is and error out.

I have looked at the source code and found there is a duplicate section for
this setting in "vino-main.c" as follows (line 232 in Pluma):
      g_settings_bind (vino->settings, "authentication-methods",
                       server, "auth-methods", G_SETTINGS_BIND_GET);
      g_settings_bind (vino->settings, "require-encryption",
                       server, "require-encryption", G_SETTINGS_BIND_GET);
      g_settings_bind (vino->settings, "require-encryption",
                       server, "require-encryption", G_SETTINGS_BIND_GET);
      g_settings_bind (vino->settings, "vnc-password",
                       server, "vnc-password", G_SETTINGS_BIND_GET);

This also occurs in "vino-perfs.c" file at line 80.

I am not totally familiar with C++ object programming and the GTK library
to know if this would cause this setting to have two bindings and get confused
in execution such that it is not taking the user setting made with 'gsettings'
command.

I see much chatter on this issue (encryption not working) with the latest Vino
and Linux Mint 17 as well as Ubuntu and other releases.

I would patch to try, but getting through ./configure successfully and
installing all the stuff needed is more than I can do on my connection.
I would test this by taking out the extra g_settings_bind function call.

Please have a check on it and hopefully clear up making this setting in the
normal GTK methods provided in Linux and having it work effectively.

Regards,
Marc Y.