public function calculateHash()
    {
        $str =  $this->data['ECM_TRANS_ID'] .
                $this->data['ECM_TRANS_DATE'] .
                $this->request->getPurse() .
                $this->data['ECM_PAYER_ID'] .
                $this->data['ECM_ITEM_COST'] .
                $this->data['ECM_QTY'] .
                $this->request->getSecret();

        return md5($str);
    }