How to display archive.php posts in random order

I have this archive.php template. It displays all the posts in the category. How can i display them in random order?

<?php if (have_posts()) : ?>
<h1 class="entry-title post-title widget-wrapper"><?php single_cat_title('',true); ?></h1>
<?php while (have_posts()) : the_post(); ?>
<?php the_title(); ?> -
<?php 		endwhile;
get_template_part( 'loop-nav' );
else :
get_template_part( 'loop-no-posts' );
endif;
?>