Deciphering a secret society manual

Around 1730 a German secret society recorded their initiation rituals in an encrypted manuscript. In 2011, that cipher was finally decoded.

Copiale cipher
18th century, Public domain, via Wikimedia Commons

I love a good cipher. Cryptography is such a fascinating battle of minds between the encrypter and the decrypter. Good codes understand decoding techniques and purposefully work against them; good code breaking recognises and adapts to those disguises. The Copiale cipher is a great demonstration of that dance.

Academics found the Copiale cipher in an East German research library in the 1970s. It was a hundred and five pages long and at least two hundred years old. The manuscript was full of dense code, incorporating normal letters, punctuation, accent marks, Greek letters, and other symbols. Only two of the words were not encrypted: “Copiales 3” and “Philipp 1866.” The rest of the writing was impenetrable.

In 2011, a team of Californian and Swedish researchers deciphered the manuscript. They began with the idea that it may be a substitution cipher. The text is written in a normal language, but each letter is swapped for a different one. If you know the original language you can break a substitution cipher by looking at letter frequencies. In English, “e” is the most common letter – so you find the most common symbol and substitute an “e.” You look for doubled symbols (they’re often “oo,” “tt,” or “ss”) and common words (“the” or “a”), and pretty soon the cipher is solved.

This approach did not work for the Copiale cipher. The manuscript had more than ninety symbols, and none of them were disproportionately common. This led the researchers down a different path, into homophonic ciphers. A homophonic cipher uses multiple symbols to represent the more common letters, so you cannot work out the common letters by analysing symbol frequencies.

The manuscript threw up another challenge. The enciphered text had no spaces, so you cannot work out where words begin and end. The researchers guessed that the non-letter symbols together acted as spaces. This would serve two purposes: hiding the words, but also acting as decoys against decoding attempts and symbol frequency attacks. The researchers were half right. The manuscript did use decoys, but the regular letters were the ones to ignore.

When they finally solved the puzzle, they revealed the truth of the manuscript. In 1738 the Catholic Church issued a papal bull (“In eminenti apostolatus”) banning Freemasonry. As a result, a group of Germans formed a secret society called the Oculists. The Copiale cipher was that society’s initiation ritual. Here’s an excerpt:

He carries him thereafter to a secondary table where, next to a lot of candles, several instruments and eye glasses, microscopic perspective, a cloth and a glass of water must be present. He has to lower himself on to a tabouret [a stool] and to look upon an unwritten piece of paper for a while.

If, after a while, he answers that he cannot see anything written on there, then the Master of Ceremonies gives him a pair of eyeglasses and asks him again if he is not able to read the writing. Answer no. During this time the Master of Ceremonies comforts him as well as he can, raises his hopes for improvement, washes his eyes with a cloth and if nothing helps, he will announce that they have to proceed with the operation.

The Copiale cipher

The “operation” was pulling out an eyebrow hair. Oh those Oculists…

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