Solving the Enigma of Kryptos

It's been nearly 15 years since Sanborn installed the 12-foot-high, verdigrised copper, granite and wood sculpture inscribed with four encrypted messages at the CIA's Langley, Virginia, headquarters in 1990. And it's been seven years since anyone made progress at cracking its code.
But publication of the novel The Da Vinci Code has renewed interest in solving the puzzle because author Dan Brown made two veiled references to Kryptos on his book's dust jacket. Brown's publisher sponsored a contest around the references, and Brown has hinted that his next book, which takes place in Washington, D.C., may feature the sculpture in some way.