Code for differing background images

I would like to have one image for the background of the “Home” page, and different for the rest of the site.

What should the code look like when I edit it to produce this?

Here is my css:

body{
background: url(images/background_port.png) no-repeat center center fixed;
-webkit-background-size: cover;
-moz-background-size: cover;
-o-background-size: cover;
background-size: cover;
}
body.home {
background:url(images/box-edit)no-repeat center center fixed;
-webkit-background-size: cover;
-moz-background-size: cover;
-o-background-size: cover;
background-size: cover;
}

Thanks.