code: @Override
      public void store(String key, byte[] payload) throws IOException {
          try {
              Cipher sym = Cipher.getInstance("AES");
              sym.init(Cipher.ENCRYPT_MODE, masterKey);
              try (
                      FileOutputStream fos = new FileOutputStream(getFileFor(key));
                      CipherOutputStream cos = new CipherOutputStream(fos, sym)
              ) {
                  cos.write(payload);
                  cos.write(MAGIC);
              }
          } catch (GeneralSecurityException e) {
              throw new IOException("Failed to persist the key: " + key, e);
          }
      }
docs: Persists the payload of a key to the disk.