The Kryptos K4 ciphertext message
The fully decrypted cleartext message
“We believe so, but we have not yet found our champion.”
A sculpture in the courtyard of the CIA, its history since 1959, and the fourth of its four messages, the one nobody has read.
Kryptos is a sculpture by the artist Jim Sanborn, dedicated in 1990 in the courtyard of the CIA's headquarters in Langley, Virginia. Its centrepiece is a curved copper screen cut through with about 1,730 letters: four encrypted messages, K1 to K4, and the table of alphabets used to encrypt the first two.
K1, K2 and K3 were solved in the 1990s. K4, the last 97 letters, has never been publicly solved. Sanborn has confirmed only two stretches of its plaintext, EASTNORTHEAST and BERLINCLOCK. In 2025 the full plaintext turned up among his papers at the Smithsonian, but it has not been published, and the method that turns the 97 carved letters into that message is still unknown.
That method is what this loop is looking for.
The history of Kryptos, from the CIA's headquarters to today. The first three messages hang off 1999, when their solutions went public: carved letters in, readable English out, which is what solved looks like.
President Eisenhower lays the cornerstone of the CIA's headquarters in Langley, Virginia.
The CIA's own pages give March 1961 for completion and the autumn of 1961 for staff moving in. Kryptos will stand in the courtyard between this building and the next.
CIA, Original Headquarters Building · CIA, Sites to See (PDF)
A small part of the New Headquarters Building's cost is set aside for art. The CIA's Fine Arts Commission recommends the GSA's Art-in-Architecture programme, and the GSA forms a selection team led by the NEA.
A combined NEA and CIA panel picks the Washington sculptor for a $250,000 commission. He reads extensively on intelligence and cryptography.
Sanborn works for four months with Ed Scheidt, the retiring chairman of the CIA's Cryptographic Center, to devise the codes; Scheidt teaches him “matrix codes.”
CIA, About the Kryptos Sculpture · Washington Post, July 19, 1999
Sanborn is at work on Kryptos the year the Wall falls. BERLIN and CLOCK will turn out to be in K4.
Sanborn does the encryption on his own during a four-day drive trucking the petrified tree from Arizona. The whole project, by his count, took two and a half years.
Director William Webster receives the solution in a sealed envelope. “We like to be tested.” Other records give November 1 or 5, and the 1999 New York Times October.
The building behind the sculpture is completed.
A task force breaks the first three messages within two days, spends one more on K4 and stops. The NSA says so publicly only in June 1999, after Gillogly; the team's names come out in March 2000.
NSA, staff processing form Z-054-98 (PDF) · NSA FOIA releases, CIA Kryptos Sculpture
A CIA analyst breaks K2 with pencil and paper on February 21, 1998, and presents K1 to K3 to a packed headquarters auditorium on March 20.
Stein, Cracking the Courtyard Crypto (CIA) · CIA Intellipedia, archived
Gillogly announces his solution on June 16; the New York Times reports Stein's earlier one the same day. The three messages, as carved and as read:
New York Times, June 16, 1999 · Gillogly's post, June 16, 1999
in: K1 as carved
How. Keyed Vigenère on the sculpture's own table, key word PALIMPSEST. Each letter stays in its place; the table changes it.
out: K1 solved
Who. Solved by David Stein (1998) and Jim Gillogly (1999), and by the NSA in 1992. The misspelling IQLUSION is Sanborn's own.
how it was solved
First letter: E is 11 in the KRYPTOS alphabet, key P is 3; 11 take away 3 is 8, which is B.
in: K2 as carved
How. The same table, key word ABSCISSA. The question marks are carved and stay where they are.
out: K2 solved
Who. Same solvers. UNDERGRUUND is carved that way; in 2006 Sanborn said one letter was left out, which changes the last words to LAYER TWO.
how it was solved
First letter: V is 22 in the KRYPTOS alphabet, key A is 7; 22 take away 7 is 15, which is I.
in: K3 as carved
How. No table: the letters are moved, not changed. Written in a grid, turned, and read off in columns; the solution is laid out here in the copper's line shape, not letter for letter.
out: K3 solved
Who. Same solvers. It quotes Howard Carter opening Tutankhamun's tomb; DESPARATLY is Sanborn's.
how it was solved
Start at place 192, then count 192 on each time: 192, 47, 239, ... wrapping past 337. The letters read SLOWLYDESP.
Named by Act of Congress in October 1998 for George H. W. Bush, director of the CIA in 1976–77, and dedicated in April 1999.
In interviews Sanborn says he used “some matrix codes Ed gave me” and “left instructions in the earlier text that refer to later text”; Scheidt says he “masked the English language.”
Sanborn says he left a letter out of K2: what was read as ID BY ROWS should read X LAYER TWO.
Letters 70–74 read CLOCK, on the 25th anniversary of the Wall's fall; the Berlin clock is named.
New York Times, November 20, 2014 · Wired, November 20, 2014
Letters 26–34 read NORTHEAST; the phrase is “in itself a riddle.”
Letters 22–25 read EAST, completing EASTNORTHEAST. Sanborn had sent it privately since April; it became public on August 24.
John Schwartz (NYT), August 24, 2020 · Schmeh, Klausis Krypto Kolumne
Sanborn announces he will sell the K4 solution at an auction timed to his 80th birthday.
Two journalists find K4's plaintext on scraps of paper among Sanborn's papers at the Smithsonian's Archives of American Art and tell him; they do not publish it. The method is still unknown.
Smithsonian, Office of the Secretary · Scientific American, October 16, 2025
On November 12, in an open letter and at the International Spy Museum, Sanborn names his 1986 Egypt trip, the 1989 fall of the Wall and the World Clock in Berlin as part of K4. On November 20 the archive sells for $962,500.
Scientific American, November 12, 2025 · RR Auction, November 21, 2025
An autoresearch loop sets out to find the method from the record alone.
In: the 97 carved letters of K4, laid out as on the copper. Out: what every candidate must produce.
in: the copper, always the same
OBKR ends the line that finishes K3, then three lines of 31
out: a reading of the same 97 places
checked: the known letters in place, and the reading turns back into the copper
scored: the loss, zero is solved
Jim Sanborn has confirmed two stretches of the hidden message: EASTNORTHEAST at positions 22 to 34 and BERLINCLOCK at 64 to 74, in accent in the panels. They are the only hard facts about the message, and every experiment leans on them.
A candidate is a full 97-letter reading of the panel. It pays ten points for each known letter it gets wrong, then a little for how far the other 73 letters sit from English, then a charge for a secret word too long to remember. Zero would be solved.
Above it, at least one known letter is wrong. Below it, all 24 are right and only the English of the rest and the length of the key remain. A dot below the line is not a solution until the text reads as English and the key is one a person could remember.
Two ways to follow the work as it goes.
Every experiment so far, 198 of them, placed by what it found against scrambled copies of the carved text, updated as each new one lands.
How each experiment built on an earlier one, family by family, in the order they ran.