By default, Dotclear does not show the password protected posts. It may be not the expected behavior, you could have wished to see the post title and excerpt and protect the content with password.
This plugin implements this feature. Be aware that it only shows private posts on homepage, it would not show them on feeds and search pages.
Every suggestion or comment is welcome :)
(See also that comment on Dotclear forums : http://forum.dotclear.net/viewtopic.php?pid=276948#p276948)