protected function _hashPassword(array $data) {
        $config = Zend_Registry::get('config');
        if (!empty($config->auth->adapters->db)) {
            $authVars = $config->auth->adapters->db;
            $credentialColumn = $authVars->credentialColumn;
            $hashMethod       = $authVars->hashMethod;
            $salt             = $authVars->salt;
            if (!empty($data[$credentialColumn])) {
                $data[$credentialColumn] = new Zend_Db_Expr($hashMethod.'(CONCAT('.
                                            $this->getAdapter()->quoteInto('?', $data[$credentialColumn]).
                                            ', '.$this->getAdapter()->quoteInto('?', $salt).'))');
            }
        }
        return $data;
    }