“Maintaining secrecy about the sculpture became a challenging part of creating Kryptos. Both Jim and I were under scrutiny by the media who wanted badly to know the answer. To be honest, I don’t know the answer. After Jim finished the sculpture, I never went back to check the code.”

Edward Scheidt  — Former CIA Head of Cryptography

Kryptos at CIA headquarters in Langley, Virginia

KRYPTOS is a sculpture by the American artist Jim Sanborn located on the grounds of the Central Intelligence Agency (CIA) in Langley, Virginia. Since its dedication on November 3, 1990, there has been much speculation about the meaning of the four encrypted messages it bears. Of the four messages, the first three have been solved, while the fourth message remains as one of the most famous unsolved codes in the world. The sculpture continues to be of interest to cryptanalysts, both amateur and professional, who are attempting to decipher the fourth passage. The artist has so far given two clues to this passage. Follow us on Twitter: @INTEL_TODAY

RELATED POST: The KRYPTOS Sculpture — An Introduction

RELATED POST: The KRYPTOS Code — How to Break a Vigenère Code

RELATED POST: The KRYPTOS Code — The Solution of Section II

RELATED POST : The KRYPTOS Sculpture — History of the NSA Involvement

RELATED POST: The KRYPTOS Sculpture — SECTION I : A KEYED Vigenère Cipher [And why the CIA lies so much about it?] — UPDATE

RELATED POST: The KRYPTOS Sculpture — SECTION III: A Transposition Cipher

UPDATE (July 9 2019) —  Intel Today believes that the CIA has recently provided new clues that have been unnoticed until now.

Please, read: The KRYPTOS Sculpture — New Clues from the CIA Website?

END of UPDATE

Background

The ciphertext on the left-hand side of the sculpture (as seen from the courtyard) of the main sculpture contains 869 characters in total (865 letters and 4 question marks).

The right-hand side of the sculpture comprises a keyed Vigenère encryption tableau, consisting of 867 letters.

In our last posts about KRYPTOS, we learned how to break a Vigenère code and we apply this knowledge to decode the entire section I and II. The section III involves a different kind of encryption method and I gave you a novel solution in our latest post. Section IV has never be decoded.

Encrypted Text of KRYPTOS Section IV

OBKR
UOXOGHULBSOLIFBBWFLRVQQPRNGKSSO
TWTQSJQSSEKZZWATJKLUDIAWINFBNYP
VTTMZFPKWGDKZXTJCDIGKUHUAUEKCAR

Two clues from Sanborn

When commenting in 2006 about his error in passage 2, Sanborn said that the answers to the first three passages contain clues to the fourth passage. [ Zetter, Kim — WIRED (April 20, 2006). Typo Confounds Kryptos Sleuths]

In November 2010, Sanborn released a clue, publicly stating that “NYPVTT”, the 64th-69th letters in passage four, become “BERLIN” after decryption. [Schwartz, John (2010-11-20). “Artist releases clue to Kryptos”. The New York Times ] [All Things Considered. “‘Kryptos’ Sculptor Drops New Clue In 20-Year Mystery”. NPR.]

Sanborn gave The New York Times another clue in November 2014: the letters “MZFPK”, the 70th-74th letters in passage four, become “CLOCK” after decryption.[ “A New Clue to ‘Kryptos’”. The New York Times. 20 November 2014.]

The 74th letter is K in both the plaintext and ciphertext, meaning that it is possible for a character to encrypt to itself. This means it does not have a weakness, where a character could never be encrypted as itself, that was known to be inherent in the German Enigma machine. It is believed that the “BERLINCLOCK” plaintext may be a direct reference to the Berlin Clock.

Sanborn further stated that in order to solve passage 4, “You’d better delve into that particular clock,” but added, “There are several really interesting clocks in Berlin.”

The KRYPTOS 2015 Workshop

REFERENCES

Kryptos — Wikipedia

Stein, David D. (1999). “The Puzzle at CIA Headquarters: Cracking the Courtyard Crypto” (pdf). Studies in Intelligence. 43 (1).

The puzzle at CIA headquarters. Cracking the courtyard crypto — CIA Website

Vigenère cipher — Wikipedia

The People of the CIA: Edward Scheidt — CIA Website

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The KRYPTOS Sculpture — SECTION IV: A few clues