This is probably just part of the story. The other part is that most systems that are that old are probably black boxes by now. Everyone who knew at one point i

This is probably just part of the story. The other part is that most systems that are that old are probably black boxes by now. Everyone who knew at one point in their life what those systems actually do has retired by now. 'Simply' adding encryption, even with other libraries as mentioned in another comment would require knowing what these systems actually do. There is no magic encryption blanket that you can just toss over things.