The manuscript seems straight out of fiction: a strange, handwritten message in abstract symbols and Roman letters meticulously covering 105 yellowing pages hidden in the depths of an academic archive.
Now, more than three centuries after it was devised, the 75,000-character Copiale Cipher finally has been broken.
The mysterious cryptogram, bound in gold and green brocade paper, reveals the rituals and political leanings of an 18th-century secret society in Germany. The rituals detailed in the document indicate the society had a fascination with eye surgery and ophthalmology, though it seems members of the society were not eye doctors.
"This opens up a window for people who study the history of ideas and the history of secret societies," said computer scientist Kevin Knight of the USC Viterbi School of Engineering, part of the international team that finally cracked the cipher. "Historians believe that secret societies have had a role in revolutions, but all that is yet to be worked out, and a big part of the reason is because so many documents are enciphered."
To break the cipher, Knight and colleagues Beáta Megyesi and Christiane Schaefer of Uppsala University in Sweden tracked down the original manuscript, which was found in the East Berlin Academy after the Cold War and now is in a private collection. They transcribed a machine-readable version of the text, using a computer program created by Knight to help quantify the co-occurrences of certain symbols and other patterns.
"When you get a new code and look at it, the possibilities are nearly infinite," Knight said. "Once you come up with a hypothesis based on your intuition as a human, you can turn over a lot of grunt work to the computer."
With the cipher, the codebreaking team began not even knowing the language of the encrypted document. But because they had a hunch about the Roman and Greek characters distributed throughout the manuscript, they isolated these from the abstract symbols and attacked it as the true code.
"It took quite a long time and resulted in complete failure," Knight said.
After trying 80 languages, the cryptography team realized the Roman characters were "nulls" intended to mislead the reader. It was the abstract symbols that held the message.
The team later tested the hypothesis that abstract symbols with similar shapes represented the same letter or groups of letters. Eventually, the first meaningful words of German emerged: "Ceremonies of Initiation," followed by "Secret Section."
For more information about the method of decipherment, visit http://stp.lingfil.uu.se/%7Ebea/copiale/
Knight now is targeting other coded messages, including ciphers sent by the Zodiac Killer, a serial murderer who sent taunting messages to the press and has never been caught. Knight also is applying his computer-assisted codebreaking software to other famous unsolved codes such as the last section of "Kryptos," an encrypted message carved into a granite sculpture on the grounds of CIA headquarters, and the Voynich Manuscript, a medieval document that has baffled professional cryptographers for decades.
But for Knight, the trickiest language puzzle of all is still everyday speech. A senior research scientist in the Intelligent Systems Division of the USC Information Sciences Institute, Knight is one of the world's leading experts on machine translation -- teaching computers to turn Chinese into English or Arabic into Korean.
"Translation remains a tough challenge for artificial intelligence," said Knight, whose translation software has been adopted by Apple and Intel, among other companies.
With researcher Sujith Ravi, who received a Ph.D. in computer science from USC in 2011, Knight has been approaching translation as a cryptographic problem, which could not only improve human language translation but also could be useful in translating languages that are not currently spoken by humans, including ancient languages and animal communication.
The National Science Foundation funded Knight's cryptography and translation research. The Copiale Cipher work was presented as part of an invited presentation at this year's meeting of The Association for Computational Linguistics.
For a video on Kevin Knight and the Copiale Cipher, visit http://www.youtube.com/watch?v=Eam0Tk-1FyI
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