code: public void finish() throws IOException, SymmetricKeyException {
          if (outStream != null) {
              if (encryptor != null)
                  outStream.write(encryptor.encrypt(null));
  
              // FileOutputStream is also closed cascadingly
              outStream.close();
              outStream = null;
  
              // Only create the key if we got all the data successfully
              blobKey = new BlobKey(sha1Digest.digest());
              md5DigestResult = md5Digest.digest();
          }
      }
docs: Call this after all the data has been added.