public function createHash($dateTime, $amount)
    {
        $storeId      = $this->getStoreId();
        $sharedSecret = $this->getSharedSecret();
        $currency     = $this->getCurrencyNumeric();
        $stringToHash = $storeId . $dateTime . $amount . $currency . $sharedSecret;
        $ascii        = bin2hex($stringToHash);

        return sha1($ascii);
    }