It is one of the world's most baffling puzzles, the bane of professional cryptologists and amateur sleuths who have spent 15 years trying to solve it. But the race to find the secrets of Kryptos, a sculpture inside a courtyard at the CIA's heavily guarded headquarters in Langley, Virginia, may be reaching a climax. And interest has soared since Dan Brown hid references to Kryptos on the cover design for his bestselling novel The Da Vinci Code, and suggested it might play a role in his next novel, The Solomon Key. The Kryptos sculpture incorporates a coded message made up...