An encryption in the courtyard
In the northwest corner of the main courtyard at the Central Intelligence Agency's headquarters in Langley, Virginia, a large, S-shaped copper screen stands next to a petrified tree and a bubbling pool. Dedicated on November 3, 1990, the sculpture, named Kryptos (Greek for "hidden"), is the work of artist Jim Sanborn. Cut through the 12-foot-tall copper plates are 1,735 alphabetic characters, forming four encrypted messages. Sanborn collaborated with Ed Scheidt, the retiring chairman of the CIA's Cryptographic Center, to design the ciphers with escalating difficulty. The complete installation includes other elements around the CIA grounds, such as granite slabs with Morse code messages and a compass rose pointing to a lodestone.
The first three sections, known as K1, K2, and K3, were solved publicly by 1999. A CIA analyst, David Stein, had deciphered them a year earlier using only pencil and paper, while computer scientist Jim Gillogly cracked them with a computer. Unknown to both, an NSA team had already secretly solved the same three parts back in 1992.
The solved passages
The first two passages, K1 and K2, use a modified form of a Vigenère cipher, a method of encrypting text using a series of interwoven Caesar ciphers based on the letters of a keyword. The decrypted text of K1 is a poetic phrase written by Sanborn: "BETWEEN SUBTLE SHADING AND THE ABSENCE OF LIGHT LIES THE NUANCE OF IQLUSION". The intentional misspelling of "illusion" was designed as a cryptographic red herring.
K2's text alludes to a buried object and includes a set of coordinates: 38° 57' 6.5" N, 77° 8' 44" W. These coordinates point to a location in the courtyard about 150 feet from the sculpture itself. The passage ends with the question, "WHO KNOWS THE EXACT LOCATION? ONLY WW." The initials "WW" refer to William Webster, the CIA Director when the sculpture was installed.
The third passage, K3, employs a more complex transposition cipher, which rearranges the order of the letters. Its decrypted text is a paraphrased quote from archaeologist Howard Carter's diary, describing the 1922 opening of the door to Tutankhamun's tomb.
The final 97 characters
The fourth and final passage, K4, consists of 97 characters that have defied decryption for over three decades. Over the years, Sanborn has released four clues to assist codebreakers. In 2010, he revealed that the letters at positions 64-69, "NYPVTT," decrypt to "BERLIN". In 2014, he announced that positions 70-74, "MZFPK," become "CLOCK". A third clue, "NORTHEAST," was released in 2020, followed by "EAST" in 2021. Even with these hints, the full meaning and the cryptographic method of K4 remain uncracked. Sanborn has also suggested that a fifth passage will be revealed once the first four are solved.