Prevent to display a post twice or more in a random order archive

Hello,

my blog will no longer be updated so I decided to show the posts in archive.php in a random order.

I use:

<?php $categ = get_query_var('cat'); ?>
<?php query_posts(array('orderby' => 'rand', 'cat' => $categ));
if(have_posts()) : ?><?php while(have_posts()) : the_post(); ?>
[...]

and works fine.

But when I go to previous pages it can happen that an already displayed post is shown again.

Is it possible to prevent this behaviour?

Thanks