public function signMessage(SamlMessage $message)
    {
        return $message->setSignature(
            new SignatureWriter(
                $this->getMetadata()
                    ->getFirstSpSsoDescriptor()
                    ->getFirstKeyDescriptor(KeyDescriptor::USE_SIGNING)
                    ->getCertificate(),
                KeyHelper::createPrivateKey($this->getPrivateKey(), '')
            )
        );
    }