private function decryptSymmetricKeyWithSystemKey($entity)
    {
        /** @var SymmetricKey $encryptedKey */
        $encryptedKey = $entity->getKey();
        $decryptedKey = null;

        $systemKey = $encryptedKey->getSystemKey();
        $privateKey = $this->keyStore->getPrivateMasterKey();

        if ($systemKey) {
            $systemKey = base64_decode($systemKey);
            $decryptedKey = $this->cryptographyProvider->decryptWithPrivateKey($systemKey, $privateKey);
        }

        return $decryptedKey;
    }