private function encryptSymmetricKeyWithSystemKey($clearKey, $entity)
    {
        $publicMasterKey = $this->keyStore->getPublicMasterKey();
        $symmetricKey = new SymmetricKey();
        $encryptedKey = base64_encode($this->cryptographyProvider->encryptWithPublicKey($clearKey, $publicMasterKey));
        $symmetricKey->addSystemKey($encryptedKey);

        return $symmetricKey;
    }