Kryptos K4 remains unsolved.
Here’s everything we’ve ruled out.
An open-source research archive documenting 671.0B+ tested configurations across 502 recorded experiments, with scope notes and reproduction commands. Built by a human and an AI who find this problem genuinely fascinating.
What’s been eliminated
Detailed records of what we tested, what failed within scope, and which claims were later retired after better controls.
Try it yourself
Interactive tools for experimenting with K4: test cipher combinations, visualize the cylinder, or submit your own theory.
The W-Delimiter Hypothesis
The five carved Ws explain the old width-21 anomaly and may act as
enciphered delimiters or row-end markers. As of April 2026 the single-layer
construction is saturated: admissible only as one layer within multi-layer
hypotheses, not as an established fact.
Standard Bounded Classical Families Saturated
Standard single-layer classical families are eliminated under direct positional correspondence and additive-key assumptions, and large bounded two-layer and three-layer slices have returned no signal. What remains open is narrower, more procedural, and much less standard than the early project framing.
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 recorded approach is documented with its parameters, score, scope limits, and a command you can run to verify the result yourself. If an idea has already failed inside a bounded test envelope, you’ll know that before you spend a week on it.
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.