The CIA headquarters in Langley is home to lost of mysteries, but one in particular has captured the attention of professional code breakers and puzzle enthusiasts for the last three decades.

Kryptos, a coded sculpture created by American artist Jim Sanborn has remained unsolved ever since it was originally installed at the CIA headquarters in November of 1990. The agency’s code breakers as well as other professional puzzle solvers around the world have been struggling to unravel the secrets of the 1,800 characters carved into the 12-foot block of copper, and although they’ve succeeded in cracking three of the coded messages created by Sanborn, the fourth and final one remains unsolved. Experts have tried every technique in the book, transposition, binary, polyalphabetic substitution, even Morse code, but so far no one has been able to decipher the 97-character-long fourth part of the Kryptos Sculpture.

Photo: Jim Sanborn/Wikimedia Commons (CC BY-SA 3.0)

Interestingly, the first three parts of the Kryptos code were solved in the first eight years after the sculpture was installed at Langley, but no one has made any progress since. That’s because, the first two parts are relatively straightforward enough that anyone with solid cryptography knowledge can figure them out. The third part is reportedly much more advanced, but the fourth, the one that everyone has been struggling with, is essentially almost impossible to solve.

Over the last 30 years, the fourth Kryptos code has been tackled by cryptography experts from the CIA, NSA as well as freelancers around the world. There’s even an international Kryptos group of thousands of code breakers and enthusiasts that work together to solve or at least help solve this mystery. Every year, some of them even meet with Jim Sanborn to hopefully get some helpful clues out of him, but over the years he has gotten better and better at keeping them guessing.

But it’s not that Sanborn refuses to help at all. In fact, he was kind enough to reveal not one, but two clues to help people solve the elusive last part of his puzzle. A few years ago he revealed that the 64th to 69th letters (NYPVTT) of the 97-letter- long message NYPVTT translate to “BERLIN”. Then a few years later, he provided another clue – Letters 70 to 74 in the code spelled CLOCK. So we know that part of the code translates to BERLIN CLOCK. He even encouraged people to “delve into that particular clock” for a better chance of deciphering the code. Sadly, that wasn’t enough to help solve the rest of the puzzle.

Jim Sanborn is now in his 70s, and some have asked what would happen if he should pass away before the final section of Kryptos is deciphered. The artist revealed that the written solution is locked away in a safety deposit box and that he has already passed it on to someone who can confirm it in case someone finally cracks the code.

Obviously, no one knows what the final part of the Kryptos code will reveal, or how it ties in with the first three parts, but some have speculated that the four parts make up a larger riddle. Sanborn remains tight-lipped about that as well.

Jim Sanborn sounds like a cryptography mastermind, but in reality Kryptos was his first cryptographic sculpture. And yet, it has managed to elude seasoned experts who have been obsessed with it for decades.