The artist who sculpted a secret message in code — in plain view in the courtyard of CIA headquarters and unsolved now for twenty years — has now provided codebreakers a tiny clue to its solution.
The final mystery of Kryptos – it means “hidden” in Greek – is known as the “Everest of codes” among the thousands of cryptographers who are obsessed with deciphering it. … Three passages were unravelled in 1999. But the fourth and toughest remains defiantly obscure, to the surprise of nobody more than Jim Sanborn, the sculptor who created the enduring puzzle.