Cabinet Noir is made by Denys Grybov, who started it in 2021 as a handy decoder for classical ciphers.
It grew into a place to learn cryptography by breaking real ciphers: every cipher has a tool, a step-by-step explanation, its history and practice puzzles. The site is free and has no ads.
The explanations, history pages and translations are written with the help of AI tools. The author reviews each page one by one; a page that has passed review carries a byline. The author holds editorial responsibility for what is published.
History pages are checked against the sources listed at the end of each page. Worked examples and challenges are generated by the same code that runs the tools, so they always match what the tools produce.
The site is available in English, French and Ukrainian. The translations are automated too and are reviewed language by language; pages that have passed review in a language say so on the page.
Everything you type into the tools is processed in your browser. It is never sent to a server and never saved.
The only thing kept is the list of ciphers you used recently, stored in your browser so the cipher picker can show it first. Clearing your browser data removes it.
Each History tab ends with the sources used for that cipher: encyclopedia articles on the cipher and the techniques used to break it, and published histories of cryptography.
For a general history of secret writing, the standard reference is David Kahn, The Codebreakers (1967).
Found a mistake in a date, an explanation or a translation, or a tool that gives a wrong result? Open an issue on GitHub: corrections are fixed and the page is updated.