Change this loop to display RAND posts?

<?php
global $data, $is_blog,$is_portfolio,$is_category,$is_search;
$is_contact_page = false;
$optionss =isset($post->ID)? get_post_meta($post->ID, 'themeton_additional_options', true):false;
if($optionss===false){ unset($optionss);}

$paged=isset($_REQUEST['infPaged'])?$_REQUEST['infPaged']:1;

if($is_category===true){
    $category = get_query_var('cat');
}
if($is_search===true){
    $search = get_query_var('s');
}

//////////////////ABOUT PAGE//////////////////////
if(get_ID_by_slug($data['first_page']) && ($is_portfolio===true || $is_blog===true) && !isset($_REQUEST['infPaged'])){
    query_posts( 'page_id='.get_ID_by_slug($data['first_page']) );
    while (have_posts ()) : the_post();
        get_template_part('post');
    endwhile;
    wp_reset_query();
}

//////////////////POSTS///////////////////////////
if($is_blog===true || $is_portfolio===true){
    //Blog page && Portfolio page
    $tt_query = "";
    if(isset($optionss['posts_perpage'])){
        $tt_query .= "posts_per_page=" . $optionss['posts_perpage'];
    }
    if (isset($optionss['blog_categories'])) {
        $includecats = implode(',', (array) $optionss['blog_categories']);
        $includecats = $includecats ? "&category_name='" . $includecats . "'" : '';
        $tt_query .= $includecats;
    }
    $query=$tt_query;
}elseif($is_category===true){
    $query='cat='.$category;
}elseif($is_search===true){
    $query='s='.$search;
}else{
    $query='';
}

$query.="&paged=$paged";

if(isset($query)&&$query){
    query_posts( $query );
}
while (have_posts ()) : the_post();
    get_template_part('post');
endwhile;
wp_reset_query();

//////////////////CONTACT PAGE////////////////////
if(get_ID_by_slug($data['last_page']) && ($is_portfolio===true || $is_blog===true) && !isset($_REQUEST['infPaged'])){
    query_posts( 'page_id='.get_ID_by_slug($data['last_page']) );
    while (have_posts ()) : the_post();
        get_template_part('post');
    endwhile;
    wp_reset_query();
}
?>

What part do I have to edit to get random posts?