function doAuthentication( $shopper_group ) {

        global $my, $acl, $user;
        $db = new ps_DB;
        $auth = !empty( $_SESSION['auth']) ? $_SESSION['auth'] : array();
        
        if( class_exists('jfactory')) {
            $vmUser = JFactory::getUser();
        } else {
            $vmUser =& $my;
        }
        if( VM_PRICE_ACCESS_LEVEL != '' ) {
            // Get the usertype property when not present
            if( empty( $vmUser->usertype ) ) {
                if( empty( $vmUser->id )) {
                    $gid = 29;
                }
                else {
                    $gid = $vmUser->gid;
                }
                $fieldname = vmIsJoomla( '1.5' ) ? 'id' : 'group_id';
                $db->query( 'SELECT `name` FROM `#__core_acl_aro_groups` WHERE `'.$fieldname.'` ='.$gid );
                $db->next_record();
                $vmUser->usertype = $db->f( 'name' );
            }
            
            $this->prepareACL();
            
            // Is the user allowed to see the prices?
            // this code will change when Joomla has a good ACL implementation
            if( is_callable( array( $user, 'authorize'))) {            
                $auth['show_prices']  = $user->authorize( 'virtuemart', 'prices' );    
            }
            else {
                $auth['show_prices']  = $acl->acl_check( 'virtuemart', 'prices', 'users', strtolower($vmUser->usertype), null, null );
            }
        }
        else {
            $auth['show_prices'] = 1;
        }

function writeconfig(&$d) {
        global $my, $db, $vmLogger, $VM_LANG, $mosConfig_live_site;

        $group_id = intval( $d['conf_VM_PRICE_ACCESS_LEVEL'] );
// TODO: (J! 1.5) Is there a better way to handle this difference between Joomla versions?
        if( vmIsJoomla(1.5) ) {
            $db->query( 'SELECT name FROM #__core_acl_aro_groups WHERE id=\''.$group_id.'\'' );
        } else {
            $db->query( 'SELECT name FROM #__core_acl_aro_groups WHERE group_id=\''.$group_id.'\'' );
        }
        $db->next_record();
        $d['conf_VM_PRICE_ACCESS_LEVEL'] = $db->f('name');

        if (!is_writable(ADMINPATH ."virtuemart.cfg.php")) {
            $vmLogger->err( $VM_LANG->_('VM_CONFIGURATION_CHANGE_FAILURE',false).' ('. ADMINPATH ."virtuemart.cfg.php)" );
            return false;
        }