The most celebrated inscription at the Central Intelligence Agency's headquarters in Langley, Virginia, used to be the biblical phrase chiseled into marble in the main lobby: "And ye shall know the truth, and the truth shall make you free." But in recent years, another text has been the subject of intense scrutiny inside the Company and out: 865 characters of seeming gibberish, punched out of half-inch-thick copper in a courtyard.

It's part of a sculpture called Kryptos, created by DC artist James Sanborn. He got the commission in 1988, when the CIA was constructing a new building behind its original headquarters. The agency wanted an outdoor installation for the area between the two buildings, so a solicitation went out for a piece of public art that the general public would never see. Sanborn named his proposal after the Greek word for hidden. The work is a meditation on the nature of secrecy and the elusiveness of truth, its message written entirely in code.

Almost 20 years after its dedication, the text has yet to be fully deciphered. A bleary-eyed global community of self-styled cryptanalysts—along with some of the agency's own staffers—has seen three of its four sections solved, revealing evocative prose that only makes the puzzle more confusing. Still uncracked are the 97 characters of the fourth part (known as K4 in Kryptos-speak). And the longer the deadlock continues, the crazier people get.

Whether or not our top spooks intended it, the persistent opaqueness of Kryptos subversively embodies the nature of the CIA itself—and serves as a reminder of why secrecy and subterfuge so fascinate us. "The whole thing is about the power of secrecy," Sanborn tells me when I visit his studio, a barnlike structure on Jimmy Island in Chesapeake Bay (population: 2). He is 6'7", bearded, and looks a bit younger than his 63 years. Looming behind him is his latest work in progress, a 28-foot-high re-creation of the world's first particle accelerator, surrounded by some of the original hardware from the Manhattan Project. The atomic gear fits nicely with the thrust of Sanborn's oeuvre, which centers on what he calls invisible forces.

With Kryptos, Sanborn has made his strongest statement about what we don't see and can't know. "He designed a piece that would resonate with this workforce in particular," says Toni Hiley, who curates the employees-only CIA museum. Sanborn's ambitious work includes the 9-foot 11-inch-high main sculpture—an S-shaped wave of copper with cut-out letters, anchored by an 11-foot column of petrified wood—and huge pieces of granite abutting a low fountain. And although most of the installation resides in a space near the CIA cafeteria, where analysts and spies can enjoy it when they eat outside, Kryptos extends beyond the courtyard to the other side of the new building. There, copper plates near the entrance bear snippets of Morse code, and a naturally magnetized lodestone sits by a compass rose etched in granite.

"People call me an agent of Satan," says artist Sanborn, "because I won't tell my secret."

Photo: Adrian Gaut

The heart of the piece, though, is the encrypted text, scrambled, Sanborn says, by "a coding system that would unravel itself slowly over a period of time."

When he began the work, Sanborn knew very little about cryptography, so he reluctantly accepted the CIA's offer to work with Ed Scheidt, who had just retired as head of Langley's Cryptographic Center. Scheidt himself was serving two masters. "I was reminded of my need to preserve the agency's secrets," Scheidt says. "You know, don't tell him the current way of doing business. And don't create something that you cannot break—but at the same time, make it something that will last a while."

Scheidt schooled Sanborn in cryptographic techniques employed from the late 19th century until World War II, when field agents had to use pencil and paper to encode and decode their messages. (These days, of course, cryptography is all about rugged computer algorithms using long mathematical keys.) After experimenting with a range of techniques, including poly-alphabetic substitution, shifting matrices, and transposition, the two arrived at a form of old-school, artisanal cryptography that they felt would hold off code breakers long enough to generate some suspense. The solutions, however, were Sanborn's alone, and he did not share them with Scheidt. "I assumed the first three sections would be deciphered in a matter of weeks, perhaps months," Sanborn says. Scheidt figured the whole puzzle would be solved in less than seven years.

During the two years of construction, there were moments of intrigue and paranoia, in keeping with the subject matter and the client. "We had to play a little on the clandestine side," says Scheidt, who talks of unnamed observers outside armed with long-range cameras and high-intensity microphones. "We had people with ladders climbing up the walls of my studio trying to photograph inside," Sanborn says. He came to believe that factions within the CIA wanted to kill the project. There were unexplained obstacles. For instance, he says, "one day a big truckload of stone for the courtyard disappeared. Never found. I saw it in the evening, went back in the morning, and it had vanished. Nobody would tell me what happened to it."

Sanborn finished the sculpture in time for a November 1990 dedication. The agency released the enciphered text, and a frenzy erupted in the crypto world as some of the best—and wackiest—cryptanalytic talent set to work. But it took them more than seven years, not the few months Sanborn had expected, to crack sections K1, K2, and K3. The first code breaker, a CIA employee named David Stein, spent 400 hours working by hand on his own time. Stein, who described the emergence of the first passage as a religious experience, revealed his partial solution to a packed auditorium at Langley in February 1998. But not a word was leaked to the press. Sixteen months later, Jim Gillogly, an LA-area cryptanalyst used a Pentium II computer and some custom software to crack the same three sections. When news of Gillogly's success broke, the CIA publicized Stein's earlier crack.

James Sanborn buried his sculpture's message so deeply that a CIA staffer took seven years to solve just the first three sections. Here's what we know.

The first section, K1, uses a modified Vigenère cipher. It's encrypted through substitution—each letter corresponds to another—and can be solved only with the alphabetic rows of letters on the right. The keywords, which help determine the substitutions, are KRYPTOS and PALIMPSEST. A misspelling—in this case IQLUSION—may be a clue to cracking K4.

K2, like the first section, was also encrypted using the alphabets on the right. One new trick Sanborn used, though, was to insert an X between some sentences, making it harder to crack the code by tabulating letter frequency. The keywords here are KRYPTOS and ABSCISSA. And there's another intriguing misspelling: UNDERGRUUND.

A different cryptographic technique was used for K3: transposition. All the letters are jumbled and can be deciphered only by uncovering the complex matrices and mathematics that determined their misplacement. Of course, there is a misspelling (DESPARATLY), and the last sentence (CAN YOU SEE ANYTHING?) is strangely bracketed by an X and a Q.

Sanborn intentionally made K4 much harder to crack, hinting that the plaintext itself is not standard English and would require a second level of cryptanalysis. Misspellings and other anomalies in previous sections may help. Some suspect that clues are present in other parts of the installation: the Morse code, the compass rose, or perhaps the adjacent fountain.

But if anyone expected that solving the first three sections would lead to a quick resolution of the whole puzzle, their hopes were soon dashed. The partial solutions only deepened the confusion.

K1 is a passage written by Sanborn. "I tried to make it sound good and be inscrutable enough to be interesting," he says. Judge for yourself how well he did: "Between subtle shading and the absence of light lies the nuance of iqlusion." Yes, iqlusion—one of several misspellings that Sanborn says are intentional. The second section reads like a telegraph transmission. There's a reference to a magnetic field and information transmitted to a specific latitude and longitude—geo-coordinates for a location a couple of hundred feet south of the sculpture itself (a spot where nothing of apparent interest lies).

K3 paraphrases a diary entry of anthropologist Howard Carter from his 1922 discovery of King Tut's tomb, ending with a question: "Can you see anything?" When Gillogly turned up that passage, he says, he had "the same excitement and exultation that Carter described. In a way, it seems that the plaintext is a metaphor for the work of the code breaker, or perhaps of the CIA itself."