In Order of the Phoenix, Sirius Black seems to know that codes exist, at least. Although he dismisses them as “breakable” and decides to communicate over a floo network connection instead (which makes me wonder if wizards know about one-time pads, and if there are any spells which can break them).
Given that the magical community didn’t seem to get into mathematics much, and provably strong crypto needs a ton of math, I could see how they never went beyond Caesar Ciphers.
In Order of the Phoenix, Sirius Black seems to know that codes exist, at least. Although he dismisses them as “breakable” and decides to communicate over a floo network connection instead (which makes me wonder if wizards know about one-time pads, and if there are any spells which can break them).
Given that the magical community didn’t seem to get into mathematics much, and provably strong crypto needs a ton of math, I could see how they never went beyond Caesar Ciphers.