code: @Override
    public Data process(Data context) throws ProcessingStageException {
      try {
        keyChain.sign(context, certificateName);
      } catch (SecurityException e) {
        throw new ProcessingStageException(e);
      }
      return context;
    }
docs: Sign a {@link Data} packet.
  
  @param context the data packet to sign
  @return the signed data packet
  @throws ProcessingStageException if signing fails