The Copiale Cipher and the secret rites of the Oculists

For more than two centuries the Copiale Cipher was an elegant and incomprehensible book: one hundred and five pages bound in gold and green brocade paper, covered in a script of abstract symbols and Greek and Roman letters. In 2011 a team of researchers deciphered it, revealing an eighteenth-century German text describing the ceremonies of a secret society. It is one of the rare mysterious manuscripts to have found a generally accepted solution.

The 2011 decipherment

The work was carried out by Kevin Knight, a computer scientist at the University of Southern California, together with Beáta Megyesi and Christiane Schaefer of Uppsala University. The first step was to work out which language was hidden. The researchers guessed that the Roman letters, easily recognisable and therefore suspect, were mostly meaningless fillers, and that the real message lay in the abstract symbols and the Greek letters.

Using statistical methods they compared the frequency of the signs with that of various European languages, and German proved the most compatible. It was a homophonic cipher: the most frequent letters could be represented by several different symbols, so as to defeat simple frequency analysis. The first words obtained were 'Ceremonien der Aufnahme', meaning 'ceremonies of admission', and from there the rest of the text followed quickly.

The society of the Oculists

The text describes the rites of a German secret society that called itself the Oculists, active in the second half of the eighteenth century. The book sets out the admission of new members and the symbolic meaning of the instruments of eye surgery. According to the manuscript, during the ceremony a hair was plucked from the candidate's eyebrow, a ritual gesture linked to the theme of sight and inner enlightenment.

Scholars believe the society was close to Freemasonry, whose language and structure it borrows, and that the eye symbolised the ability to see the truth. One hypothesis put forward is that it served to preserve and pass on Masonic rituals after the condemnation of Freemasonry issued by Pope Clement XII in 1738. It is a textbook case of the culture of secret associations in Enlightenment Europe.

A name taken from the last page

The name 'Copiale' is not old: it comes from a word that appears at the end of the manuscript, one of the few notes written in plain text. The codex was in the archive of the East Berlin Academy of Sciences and, after the end of the Cold War, emerged from obscurity as a cryptographic curiosity, before being studied systematically and finally read in full.

The decipherment was made possible by combining human intuition with computing. The same approach was later extended to other historical ciphers kept in European archives, opening a small field of research devoted to the encrypted documents of the past, from diplomatic letters to the registers of confraternities, many of which are still waiting to be read.

The Copiale Cipher reminds us that not all mysterious manuscripts hold cosmic revelations. Sometimes the secret is more human and closer to us: the rituals of a group of gentlemen who wanted to protect their ceremonies from the eyes of outsiders, and who entrusted an invented alphabet with the task of keeping them hidden.