After more than three decades as the world's most famous unsolved code, the 97-character plaintext solution to the final cipher of the Kryptos sculpture, known as K4, is set to be monetized. Artist Jim Sanborn is releasing the answer during a high-profile auction scheduled for November 20, 2025, marking a significant turning point for the iconic public artwork installed at the CIA headquarters in Langley, Virginia, in 1990.
Kryptos features four distinct coded messages etched into its copper and granite structure. While the first three segments yielded their secrets to codebreakers throughout the 1990s, K4 has remained an impenetrable barrier, drawing countless attempts from cryptographers and enthusiasts globally. Sanborn stated that the decision to sell the answer stems from the overwhelming volume of inquiries, which he noted has recently been polluted by inaccurate, machine-generated solutions, and because he no longer possesses the necessary physical, mental, or financial resources to maintain stewardship of the code.
The formal sale is being conducted by RR Auction, with pre-sale estimates suggesting the winning bid could range between $300,000 and $500,000. The lot is comprehensive, encompassing not only the original handwritten plaintext of K4 but also a 12-by-18-inch copper plate that Sanborn used as a crucial 'proof-of-concept' artifact during the sculpture's creation. The offering also includes other archival materials, such as a signed letter from former CIA cryptographer Ed Scheidt, who collaborated with Sanborn on the piece.
Sanborn, who will be celebrating his 80th birthday around the time of the auction, expressed a hope that the eventual custodian of this knowledge will exercise discretion and maintain confidentiality for a period. He also suggested that the buyer might oversee a structured system for validating future cracking attempts, recognizing that the puzzle's enduring value lies in the ongoing human engagement with the unknown. The sculpture itself, a collaboration between Sanborn and Scheidt, was intended to challenge cryptanalysts, and its dedication on November 3, 1990, was anticipated to be solved within five to ten years.