When commenting in 2006 about his error in passage2, Sanborn said that the answers to the first three passages contain clues to the fourth passage. Sanborn gave
The New York Times another clue in November 2014: the letters "MZFPK", the 70th through 74th letters in passage4, become "CLOCK" after decryption. The 74th letter is
K in both the plaintext and ciphertext, meaning that it is possible for a character to encrypt to itself. Sanborn further stated that in order to solve passage4, "You'd better delve into that particular clock", but added: "There are several really interesting clocks in Berlin." In 2025, Sanborn confirmed that the plaintext referred to the
World Clock. In an article published on January 29, 2020, by
The New York Times, Sanborn gave another clue: at positions 26 to 34, ciphertext "QQPRNGKSS" is the word "NORTHEAST". In August 2020, Sanborn revealed that the four letters in positions 22 through 25, ciphertext "FLRV", in the plaintext are "EAST". Sanborn commented that he "released this layout to several people as early as April".
Auction In an August 2025 letter to
The Washington Post, Sanborn announced his plan to auction off the solution for the final passage, writing that he hoped the buyer would keep the fourth passage a secret, offering the following clue: "If they don't then (CLUE) what's the point? . . . Power resides with a secret not without it." He stated that he planned to auction off the solution for the fourth passage on November 20, his 80th birthday. It was auctioned by
Boston-based
RR Auction and had been expected to fetch a price between $300,000 and $500,000. In the same letter, Sanborn wrote that the decision to sell the solution "has not been an easy one" and acknowledged "many in the Kryptos community will find it upsetting," but, "I no longer have the physical, mental or financial resources" to maintain the code and continue other projects. The Kryptos archive ultimately sold for $962,500 at the conclusion of the auction. Shortly thereafter, Sanborn asked the Smithsonian to seal the relevant files for the next 50 years (until 2075), and they complied. After consulting with the auction house, Sanborn requested Kobek and Byrne to sign
NDAs, which they refused. Kobek and Byrne mentioned sifting through several other examples of Sanborn's work in the Smithsonian archives before stumbling across the K4 plaintext, as during an interview with
Wired News in 2005, Sanborn was asked if it was important to look at his other works, before and after Kryptos, to understand Kryptos. His response was "For the student of cryptography it's always helpful to gather as much information as possible when zeroing in on and encoding a system." == Related sculptures ==