public function toXML(DOMNode $parentElement = null) : DOMElement
    {
        if ($parentElement === null) {
            $document = DOMDocumentFactory::create();
            $parentElement = $document;
        } else {
            $document = $parentElement->ownerDocument;
        }

        $root = $document->createElementNS(Constants::NS_SAML, 'saml:'.'EncryptedAssertion');
        $parentElement->appendChild($root);

        $root->appendChild($document->importNode($this->encryptedData, true));

        return $root;
    }