Index: wp-includes/post-template.php
===================================================================
--- wp-includes/post-template.php	(revision 15246)
+++ wp-includes/post-template.php	(working copy)
@@ -317,11 +317,15 @@
 	$classes[] = $post->post_type;
 	$classes[] = 'type-' . $post->post_type;
 
+	// post requires password
+	if ( post_password_required($post->ID) )
+		$classes[] = 'post-password';
+
 	// sticky for Sticky Posts
 	if ( is_sticky($post->ID) && is_home() && !is_paged() )
 		$classes[] = 'sticky';
 
-	// hentry for hAtom compliace
+	// hentry for hAtom compliance
 	$classes[] = 'hentry';
 
 	// Categories