Login and Register are the same page.  The default login page is a modification of the home page.  While I haven't tried it, making the home page secure might secure the login page.  If you want a separate login page, create one and put the login module on it.  Then, you can visit that page's settings to secure it.  You make this the default login page under Site Settings.

For that admin pages, some of the techniques outlined in How to limit access to the admin menu might show you how to get to the admin and host pages to secure them.