The Kryptos sculpture
Since 1990 a curved copper screen by the artist Jim Sanborn has stood in a courtyard at CIA headquarters in Langley, its surface cut with about 1,800 letters. The text hides four messages, K1 through K4. Three have been solved; the fourth has resisted every attack for three decades and is one of the most famous unsolved ciphers in the world.
K1 and K2 are Quagmire III ciphers — Vigenère variants over an alphabet mixed with the keyword KRYPTOS. Sanborn even carved the cipher table onto the sculpture's other half. Because every tool on this site runs in your browser, you can decrypt the real ciphertext yourself.
K1 — key PALIMPSEST
EMUFPHZLRFAXYUSDJKZLDKRNSHGNFIVJYQTQUXQBQVYUVLLTREVJYQTMKYRDMFD
Sixty-three letters that decrypt to a sentence of Sanborn's own, with the deliberate misspelling IQLUSION.
K2 — key ABSCISSA
The longest solved section: 369 letters pointing to something "buried out there", complete with compass coordinates. The carved text contains a famous flaw — Sanborn omitted a letter, so the decryption ends IDBYROWS where he intended X LAYER TWO. He confirmed the correction in 2006. The misspelling UNDERGRUUND is deliberate.
K3 and K4
K3 changes method entirely: it is atransposition — the letters of a passage from Howard Carter's diary on opening Tutankhamun's tomb ("Can you see anything?") are rearranged by a double rotation rather than substituted. The cipher identifier shows the telltale signature: English letter frequencies, unreadable text.
K4 is 97 letters and still unsolved. Sanborn has released four plaintext cribs — BERLIN, CLOCK, EAST NORTHEAST, and BERLIN CLOCK — and the known letter positions rule out every simple system on this site, which is exactly why it endures. In 2025 Sanborn auctioned the solution, sealed, for the benefit of his estate; the cipher itself remains open to anyone with a pencil.