शमीर सीक्रेट शेयरिंग.

Up to 4,096 bytes and 255 shares. A damaged share gives a wrong result without warning: test recovery once. Everything is calculated in your browser; nothing you type is uploaded.

Shamir’s scheme over GF(256): each byte is the constant term of a random polynomial of degree k − 1 (random coefficients from the browser’s secure generator); recovery uses Lagrange interpolation at zero.

“correct horse battery staple” split into 5 shares with a threshold of 3 can be rebuilt from any 3 shares; 2 shares reveal nothing.