Kryptos K4 remains unsolved.
Here’s everything we’ve ruled out.
An open-source research archive documenting 671.0B+ tested configurations across 476 experiments, with reproduction commands for every one. Built by a human and an AI who find this problem genuinely fascinating.
What’s been eliminated
Detailed records of every encryption method we’ve tested and ruled out, organized by type, with confidence ratings and full methodology.
Try it yourself
Interactive tools for experimenting with K4: test cipher combinations, visualize the cylinder, or submit your own theory.
The Stehle Anomaly
A constant-difference pattern at positions 55–63. Every 4th character differs by exactly 5. Unique in K4 (p ≈ 1/642 after correction).
Read more →Every Classical Cipher Eliminated
All standard single-layer cipher families have been tested and eliminated under direct positional correspondence. Multi-layer and running-key models remain open.
Read more →Why this exists
Kryptos K4 has been unsolved for 35 years. In that time, thousands of people have independently tried the same approaches (Vigenère with every keyword, columnar transposition at every width, Beaufort with every alphabet) and hit the same walls, alone, with no way to know someone else already tried it.
This site is an attempt to fix that. Every approach we’ve tested is documented with its parameters, its score, and a command you can run to verify the result yourself. If an idea has already been eliminated, you’ll know before you spend a week on it. If it hasn’t, you’ll know that too.
The project started as one person’s obsession with a sculpture and grew into a collaboration between a human researcher and Claude, an AI that turned out to be an excellent partner for exhaustive cryptanalysis. The codebase is open source. The findings are reproducible. The failures are documented as carefully as the successes.
We haven’t solved K4. But we’ve mapped a lot of the territory where the answer isn’t.
Kryptos
is an encrypted sculpture at CIA headquarters containing four messages. K1–K3 were solved in 1998–1999. K4
(97 characters) has resisted all public cryptanalytic
attempts for over 35 years. 24 plaintext characters are known:
EASTNORTHEAST at positions 21–33 and
BERLINCLOCK at positions 63–73.
Learn more →
Bespoke
Non-standard methods inspired by the physical sculpture or military cipher systems. These approaches don't fit neatly into classical categories. Includes DRYAD charts, Morse code analysis, and coordinate-based approaches.
Fractionation
Methods that break each letter into smaller pieces (like grid coordinates), scramble those pieces, then reassemble them into new letters. Includes Bifid, Playfair, Four-Square, and ADFGVX.
Key Models
Different ways to generate the secret key: from a passage in a book, from a date, from a mathematical formula, or from the sculpture itself. Includes running keys, autokey, and keyword-derived approaches.
Multi Layer
Combined approaches that stack multiple encryption steps. For example, replacing letters first, then scrambling their order. Includes null extraction, cascaded layers, and joint optimization.
Substitution
Methods that replace each letter with a different letter using a key or pattern, like a secret alphabet. Includes Vigenère, Beaufort, Quagmire, Hill, and more.
Transposition
Methods that scramble the order of letters without changing them, like writing a message into a grid and reading it back in a different order. Includes columnar, rail fence, route, and grille ciphers.