Language scholars solved 18th-century cipher

The coded manuscript, "The Copiale Cipher," has 105 pages and contains 75,000 characters. The cipher includes everything from Latin and Greek letters to diacritical signs and mystical symbols.

The manuscript, called "The Copiale Cipher," has 75 pages and contains 75,000 characters. Apart from what is the bookmark of the former owner ("Philipp 1866") and a note at the bottom of the last page ("Copiales3") the manuscript is entirely in code. The cipher used consists of 90 different characters ranging from Latin and Greek letters to diacritical signs and mystical symbols, so-called logograms.

The technique the scholars used to break the code involves comparing the most common combinations of characters in the coded document with the most commonly occurring character combinations in the underlying language. The computer program used in this deciphering was written by Kevin Knight at the Information Sciences Institute, University of Southern California.

“We didn’t even know what language lay behind the cipher. After many experiments that did not yield any preferences for any particular language, we guessed German, since the bookmark Philipp in the book had German spelling and the book, as far as we know, comes from Germany,” says Beáta Megyesi, a language technologist at Uppsala University.

A further complication for the researchers was that the cipher is homophonic, meaning that each character can be coded with several different characters in the cipher.

“At first we thought it was the Latin letters that contained the message itself, not the abstract symbols, but this proved to be wrong. The Latin letters stand for spaces in the document, presumably to lead decoders astray,” says Beáta Megyesi.

Another discovery was the significance of the colon as a marker that the preceding character is to be repeated. The researchers were able to decipher the logograms last, once they had transcribed the entire document. They represent various roles and concepts in the secret society behind the manuscript. The deciphered text itself required only 16 pages.

The manuscript was determined to come from the Oculists, a secret society whose purpose was, among other things, to map the secret rituals of the Masons. The contents of the manuscript are now being studied by scholars from the fields of history of ideas and science of religion, as they reveal information about secret societies, which were common in the 18th century, and their influence on the French and American revolutions, for instance.

The book is bound in beautiful green and yellow brocade and written on high-quality paper with two different watermarks. They have been dated to the 1760s-1780s by Per Cullhed at Uppsala University Library, Carolina Rediviva. But according to Andreas Önnerfors, a history of ideas scholar at Lund University, the text is roughly 25 years older than the book.

“The project is a good example of international interdisciplinary collaboration involving computer scientists, language technologists, linguists, codicologists, and intellectual historians. Our aim has been to use the latest technology to reveal the contents of and present the historical manuscript to experts in different branches of science and the general public,” says Beáta Megyesi.

The research team has digitized, transcribed, and decoded the entire manuscript. The contents have also been translated from German into English.

More information about the manuscript and the project as well as images of the text for downloading can be found here.