None of your cited examples are "secure," they're the very definition of "security by obscurity," which is to say insecure. https://en.wikipedia.org/wiki/Kerck

None of your cited examples are "secure," they're the very definition of "security by obscurity," which is to say insecure. https://en.wikipedia.org/wiki/Kerckhoffs%27s_principle https://en.wikipedia.org/wiki/Kerckhoffs%27s_principle