Password protection template and automatic fall in post type

I solve in this way.
In the custom template page, that contain the loop of custom post type I add this code:

<?php
/** Template Name: Restrict Area */
get_header(); 
?>

<?php if ( ! post_password_required() ) { ?>

//content of the page with loop of custom post type 

<?php } else{ 

    echo get_the_password_form($post->ID); 

} ?>

<?php get_footer(); ?>

In single-custom-post-type.php this code:

 <?php get_header(); ?>

 <?php
 if ( !post_password_required(id_page_custom_template) ) : ?>

 //content single

<?php else: ?>

    <?php echo get_the_password_form(id_page_custom_template); ?>    

<?php endif; ?>

<?php get_footer(); ?>

Where id_page_custom_template must be replaced with the id of the page with custom template.