Kaveh Waddell: What’s the earliest example of humans encrypting their everyday language to keep it secret from others?

Gerhard Strasser: There is one very well written-up and documented cuneiform tablet in Mesopotamia, found around 1500 B.C. It was an encrypted message in which craftsmen camouflaged the recipe for a pottery glaze that was a highly coveted item at the time. As it turns out, later on, the secret had been unearthed and discovered, so later recipes were no longer encrypted because just about everyone knew it.

That was an interesting detail from a city along the banks of the Tigris River around 1500 B.C. So very early on, there certainly were commercial interests in cryptographic communication, as much as there may well have been military interests.

Waddell: Do we know how that message, the recipe, was encrypted?

Strasser: It was encrypted through a relatively simple substitution method: One cuneiform symbol was used for another. That way, basically, the message got garbled. But it was good enough for any layman—anyone not initiated—not to decipher it.

Waddell: This is a very early example. Is it isolated, or do we keep seeing basic forms of encryption in the centuries that follow?

Strasser: It was relatively isolated, quite frankly. It’s very early, obviously preceding Roman and Greek examples. You probably have heard of the atbash system, which certainly predates the birth of Christ. Again, a simple replacement of the last letter in the alphabet with the first letter, the second-to-last with the second—a simple transposition of letters which was good enough, and was used in the Bible.

So we have Hebrew ciphers. We also have—and this I found surprising—a mention, and a rather serious one, in the Kama Sutra, in India, from about the 4th century. We actually have a reference in the 44th and 45th chapters that men and women should practice cryptography.

Waddell: That’s not what one usually imagines is in the Kama Sutra. Why is this book talking about cryptography?

Strasser: Well, the Kama Sutra deals with, primarily, all sorts of—shall we be neutral?—intercommunication between men and women. Such communication obviously could entail secret communication. It’s that communication where men and women should have a language of their own, so that the neighbors could not understand.

Waddell: It sounds like different forms of cryptology developed early on in separate parts of the world. Were different techniques developed separately—did they crop up on their own—or was there a sharing of techniques?

Strasser: The sharing of techniques came later. Early cryptology began with the spread of a new religion and the Arab conquest, for five major reasons. Very early on, the Arab World had to rely on translations; it also had to study its own language. There were well-known advances in mathematics. There was a need for effective administration in the Arab Muslim state, a realm that kept on spreading. And ultimately, there was the very early diffusion of reading and writing.