For nearly 16 years, puzzle enthusiasts have labored to decipher an 865-character coded message stenciled into a sculpture on the grounds of the Central Intelligence Agency's headquarters in Langley, Va. This week, the sculptor gave them an unsettling but hopeful surprise: part of the message they thought they had deciphered years ago actually says something else.
The sculpture, titled "Kryptos," the Greek word for "hidden," includes an undulating sheet of copper with a message devised by the sculptor, Jim Sanborn, and Edward M. Scheidt, a retired chairman of the C.I.A.'s cryptographic center.
The message is broken into four sections, and in 1999, a computer programmer named Jim Gillogly announced he had figured out the first three, which include poetic ramblings by the sculptor and an account of the opening of King Tut's tomb. The C.I.A. then announced that one of its physicists, David Stein, had also deciphered the first three sections a year earlier.
On Wednesday afternoon, Mr. Sanborn left a phone message for Elonka Dunin, a computer game developer who also runs an e-mail list for enthusiasts trying to solve the "Kryptos" puzzle. For the first time, Mr. Sanborn had done a line-by-line analysis of his text with what Mr. Gillogly and Mr. Stein had offered as the solution and discovered that part of the solved text was incorrect.
Within minutes, Ms. Dunin called back, and Mr. Sanborn told her that in the second section, one of the X's he had used as a separator between sentences had been omitted, altering the solution. "He was concerned that it had been widely published incorrectly," Ms. Dunin said.
Mr. Sanborn's admission was first reported Thursday by Wired News.
Ms. Dunin excitedly started sending instant messages online to Chris Hanson, the co-moderator of the "Kryptos" e-mail group. Within an hour, Ms. Dunin figured out what was wrong. The last eight characters of the second section, which describes something possibly hidden on C.I.A. grounds, had been decoded as "IDBYROWS" which people read as "I.D. by rows" or "I.D. by Row S."
In an interview yesterday, Mr. Sanborn said he had never meant that at all. To give himself flexibility as he carved the letters into the copper sheet, he had marked certain letters that could be left out. In the second passage, he left out an X separator before these eight letters.
"It was purely an act of aesthetics on my part," he said.
He said he expected that the encryption method, which relies on the position of the letters, would transform that part of the message into gibberish, and that the solvers would know to go back and reinsert the missing separator. But "remarkably, when you used the same system, it said something that was intelligible," Mr. Sanborn said. He decided to let the code breakers know about the error because "they weren't getting the whole story," he said.
When Ms. Dunin reinserted the X, the eight characters became "LAYERTWO." She called Mr. Sanborn again, who confirmed that was the intended message. "It's a surprise, and it's exciting," Ms. Dunin said. That is the first real progress on "Kryptos" in more than six years. Now to figure out what it means.
In an e-mail interview, Mr. Gillogly said that the corrected text, "layer two," is "intriguing but scarcely definitive." He added, "Like much of the sculpture, it can be taken in many ways." Mr. Gillogly, who has not worked much on the puzzle in recent years, said he would go back to see if the answer was now apparent.
One possibility is that "layer two" is the crucial key for solving the rest of the puzzle. Or it could be a hint that the letters need to be layered atop one another. Mr. Sanborn and Mr. Scheidt have said that even when all of the text is unraveled, other puzzles will remain in "Kryptos."
"This new discovery could possibly make it easier to crack and possibly not make it easier to crack," Mr. Sanborn offered unhelpfully. "It may be a dead-end diversion I like to send people on, a primrose lane to nowhere."
Mr. Scheidt said it had taken only three or four months to devise a puzzle that has lasted nearly 16 years, adding that only he, Mr. Sanborn and "probably someone at C.I.A." know the answer.
For everyone else, the remaining 97 letters of the fourth section remain baffling (the slashes indicate line breaks):