Unbroken: The codes we cannot crack

Secret radio broadcasts, a coded confession from a serial killer, and an entire book written in an unknown language. These are the illusive conundrums that have tantalised and challenged code-breakers for decades.

America’s Federal Bureau of Investigation turned to the public on Tuesday for help in solving a 1999 murder case. The body of 41-year-old Ricky McCormick was found dumped in a field in St. Louis, Missouri. The only clues to the killer’s identity were two coded notes in McCormick’s trouser pocket. Family members say he had written such notes since he was a boy, but nobody knows how to decipher them.

“Breaking the code could reveal the victim’s whereabouts before his death and could lead to the solution of a homicide,” said Dan Olson, chief of the FBI’s code-cracking unit. “Standard routes of cryptanalysis seem to have hit brick walls. Maybe someone with a fresh set of eyes might come up with a brilliant new idea.”

In making the appeal, the FBI also hopes that someone from McCormick’s past will come forward with more of his coded notes. Deciphering those could unlock the secrets written shortly before his death, revealing his final thoughts and, perhaps, bringing his killer to justice.

It is a case that is sure to capture the public’s imagination. People have long been fascinated by cryptography — the scrambling of information to control who can, and cannot read it. What child hasn’t used codewords to communicate under the radar of parents and teachers?

For as long as people have created codes, others have tried to break them. It can be a life-and-death effort: think Bletchley Park unravelling the German military ciphers during World War II. For others it is an obsession more akin to solving a sudoku or crossword puzzle; they are compelled to solve it merely to see if they can.

The opposing disciplines of cryptography and code-breaking have matured to such a state that modern computer ciphers are either cracked within days, or soon shown to be unbreakable. Bulletproof encryption is a rich business. One manufacturer of a secure memory stick is offering a $250,000 reward to anyone who can bypass its encryption, the theory being that nobody will succeed and the unclaimed reward becomes a marketing brag.

Most fascinating to many code-breakers are the ciphers that remain unbroken, some for decades, but which are believed — through instinct or analysis — to be solvable. Of these, the greatest attention is focused on so-called shortwave number stations.

For almost as long as shortwave radio has existed, picked up around the world have been broadcasts that consist of a recorded voice reciting a stream of numbers, assumed to represent encrypted messages. The messages are hidden in plain sight, so to speak — anyone can listen in, but only those with the decryption key will understand. The popular theory, that these broadcasts communicate instructions to spies, was bolstered by the 2001 prosecution of Cuban spies by the US government, which cited the use of encoded shortwave broadcasts.

One quite unique station, known as The Buzzer and traced to a site near Moscow, has broadcast beeps, and latterly buzzing noises, for 20 years, interrupted very rarely by a voice that speaks a sequence of Russian names. The scarcity of these voice broadcasts has stalled decoding efforts, and even with a flurry of activity in 2010 the meaning of the broadcasts remains unknown.

Does a cryptogram from 1970 conceal the identity of the person who shot and stabbed to death at least five people in California? Throughout his murderous spree, during which he injured many others, the Zodiac Killer sent demands and threats to newspapers, including encrypted messages. Decoded, these messages revealed the killer’s disturbing reflections on his crimes (“I like killing people because it is so much fun … when I die I will be reborn in paradise and the ones I have killed will become my slaves”) but some messages resisted code-breaking attempts. In one note the killer claimed to give his name, but the 13-letter code has proved impenetrable, and the identity of Zodiac remains unknown.

Shepherd’s Monument in Staffordshire has a number of peculiarities relating to its mirror-image engraving of a Nicolas Poussin painting. Cryptologists focus on an unexplained addition to the 18th century monument: the letters “OUOSVAVV”. Interpretations of this apparent code range from it being a dedication of love to a departed wife, clues to the location of the Holy Grail, a statement questioning the divinity of Jesus, and various biblical references. One elaborate decryption technique translates the engraving as simply the word mason.

The Voynich Manuscript is a 200-page book of unusual anatomical, botanical, astronomical and medical illustrations, dating back at least 400 years, during which time it was traded around Europe, baffling any cryptologist that tackled it. The text, thought to be encrypted, is noted for its fluidity and natural structure, leading scholars to believe that the author perfectly understood what he was writing, as opposed to encoding it as he went along. Partial translations have been put forward, but a full and convincing solution has yet to be found.

On 1 December 1948 the well-dressed body of a middle-aged man was found on a beach in Adelaide, Australia. He carried no identification and the labels were missing from his clothes. A police investigation failed to identify him and no cause of death was established. More than six months after the discovery of the man’s body, a fragment of paper was found in his trouser pocket. It bore the text “Tamám Shud”, which experts recognised as coming from The Rubaiyat, a collection of Persian poems. The book was traced: a man had found it in his unlocked car, the night before the unidentified body had been found. Inside the book were five lines of handwritten code. As with most other aspects of this complex and bewildering case, the meaning of the code has remained a mystery, re-visited over the years but never solved.