The ancient Greeks were said to be the first people who used encryption. Every coded message was comprised of two parts: the message itself, and a cipher that decoded it. The most famous set was the scytale a stick of set diameter that, when a piece of parchment with a coded string of text was wrapped around it, the message was legible across the face of the stick.
This was a beautiful solution to the problem of keeping secrets from those not in-the-know. All the receiving party needed was a stick of the right diameter and they could decode any message. In the case of the scytale, “encryption” was writing the message in such a way that it would be unintelligible without having the right decoder stick.