Sito: https://cryptpad.fr/
Source code: https://github.com/xwiki-labs/cryptpad
This project uses the CKEditor Visual Editor, CodeMirror, and the ChainPad realtime engine.
How It Works
CryptPad uses a variant of the Operational transformation algorithm which is able to find distributed consensus using a Nakamoto Blockchain, a construct popularized by Bitcoin. This way the algorithm can avoid the need for a central server to resolve Operational Transform Edit Conflicts and without the need for resolving conflicts, the server can be kept unaware of the content which is being edited on the pad.