$ssh->auth_publickey($SSH_USER, './virt_pub', './virt_priv.ppk') or die "pk connection error $!\n";

##</code><code>##

# you need  permission to read the keys
$ssh2->auth_publickey('zentara',
                 '/home/zentara/.ssh/id_dsa.pub',
         '/home/zentara/.ssh/id_dsa',
          $pass );