I guess my point in asking is that only casual security is provided by sub's, so it's little more than preventing one from reading over your shoulder, yes?
Depends on what you are talking.
In Freemasonry there is a method to aid memory, which is sometimes call a masonic cypher, by cypher by description isn't really what it is.
This sentence I have written would be displayed like the following.
T S I H W W B D L T F.
Basic initial which is a visual prompt. It is not unique to Freemasonry, and is used by many actors and public speakers.
The one I mentioned used in Mark masonry could be described as an anti-reading mechanism, although the cypher is the same as taught to most scouts, and is definitely not unique to Freemasonry and is not really intended to keep something private. The cyphered items are not secret and the imagery of the cyphered text is used to encourage thought, and asks the mason to try and work them out. Basically to get them to look for what they already know.
Helen Fouche Gaines has an excellent book on cryptography, including the solution of poly's. The appendix has all of the frequency and contact frequency tables that an amateur solver would need.
Sounds an interesting read.