For 19 years it has sat beyond the public's gaze in an inner courtyard on the campus of the Central Intelligence Agency, a not uninteresting sculpture with 865, apparently randomly selected letters perforating a solid scroll of copper.
But Kryptos is not merely a sculpture, and artist Jim Sanborn chose its constituent letters in a far from random fashion. They make up a code so complex that even the CIA's most esteemed cryptologists can't crack it.
Everyone at the CIA has known this for years. But when a novel called The Da Vinci Code appeared, a whole new crowd of crypto-geeks started paying attention. Today, the puzzle is the object of almost obsessive interest to thousands of amateur code-crackers worldwide. And the object of their obsession begins as follows: ‘EMUFPHZLRFAXYUSDJKZLDKRNSHGNFIVJ'. Pardon?
“The whole thing is about the power of secrecy,” Mr Sanborn (63) gaily explains in the new edition of Wired magazine. But if the cultish notoriety of the 10ft-high sculpture, dedicated in the CIA's Langley, Virginia, headquarters in 1990, has been a mild irritant to the agency so far — the last of four parts of the riddle remains unsolved even today — matters might be about to get much worse. And Mr Brown, whose second book, Angels & Demons, crashed on to our cinema screens this weekend, may once again be to blame.
Before a bestselling author stuck his oar in, Kryptos's life at Langley was rather quieter. It was seven long years from its 1990 unveiling before the first part of the four-section cypher was broken, a hiatus that astonished its creator: he had assumed that the all-powerful intelligence agency would crack his code within a matter of weeks.
The answer to that chunk took its first solver, a CIA employee called David Stein, 400 hours of his own time to break. The two lines of nonsense that started the code came out as “Between subtle shading and the absence of light lies the nuance of iqlusion” — the last word a deliberate misspelling of occlusion to further throw dedicated codebreakers off the scent.
The complexity of the puzzle is all the more remarkable considering that Sanborn knew little about the art of encryption before he started on the project. To help with the commission, the CIA loaned him a retiring cryptographer, Ed Scheidt.
True to espionage form, mild paranoia crept in: Scheidt would meet Sanborn at secret locations where he taught him the basics of secret code writing as practised by European spies from the late 19th Century through to the Second World War. As they progressed, however, Sanborn ensured that even Scheidt would not know the final answers.
All of those complications help explain why the last section of the code is now considered the Everest of the code-breaking world.
Even with the help of a Pentium processor and a sophisticated cryptographic program, the amateur aficionado who broke the rest of the cipher, Jim Gillogly, could not solve its final mystery.
Even mere rumours of Sanborn’s work at Langley making the pages of the next Dan Brown novel is catapulting it into a spotlight brighter than any of his contemporaries could even dream of.
Such a spotlight could lead to a renewed spurt of obsessive work on the code, and a solution; if not, Sanborn insists, he wouldn't much mind.
“In some ways, I'd rather die knowing it wasn't cracked,” he says. “Once an artwork loses its mystery, it's lost a lot.”