This content originally appeared on DEV Community and was authored by nchika
Horcrux is a TypeScript library for splitting files into encrypted fragments — “horcruxes” — inspired by Harry Potter. Think of it as digital horcruxes for your sensitive files. You can split your files into multiple pieces where only a subset is needed to restore the original — no password required.
The original idea comes from jesseduffield/horcrux — the CLI tool from the lazygit author that slices a file into N shares and restores it when any M shares are present.
I wanted a version that plugs into both Node and React Native projects, so “Yet Another Horcrux” became a library.
Repo: https://github.com/nao1215/horcrux
npm: https://www.npmjs.com/package/@nao1215/horcrux
How to use
The API stays simple: use split and bind for files, splitBuffer and bindHorcruxes if you’re juggling data in memory. Both sides run on Node and React Native.
Use files
import { split, bind, nodeAdapter } from '@nao1215/horcrux';
import { saveHorcruxes } from '@nao1215/horcrux/core/split';
// Split a file into 5 pieces, need 3 to restore
const result = await split('secret.pdf', 5, 3);
// Save horcruxes (creates secret_1_of_5.horcrux, etc.)
const files = await saveHorcruxes(result.horcruxes, './output', nodeAdapter);
// Later: Restore from any 3 horcruxes
await bind(files.slice(0, 3), 'restored_secret.pdf');
Use buffer
import { splitBuffer } from '@nao1215/horcrux';
import { bindHorcruxes } from '@nao1215/horcrux/core/bind';
const data = Buffer.from('Secret message');
const result = await splitBuffer(data, 'message.txt', {
total: 4,
threshold: 2
});
const restored = await bindHorcruxes(result.horcruxes.slice(0, 2));
console.log(restored.data.toString()); // 'Secret message'
How it works
Under the hood it’s Shamir’s Secret Sharing (SSS).
First the file is encrypted, then the encryption key is encoded as coefficients of a polynomial. Each share gets the ciphertext plus a polynomial evaluation. Set a threshold t and total n; as soon as t shares show up, Lagrange interpolation reconstructs the polynomial and the key drops out.
Sit at t-1 and you’re stuck with infinite candidates — guessing isn’t happening. Each share isn’t just “n equal slices”; it carries redundant structure to make the threshold trick work while staying useless alone.
Why did I make this?
In Japan, there’s an internet meme: “If I die, destroy my HDD (or SSD).”
My counterpoint: “I’ve split my files with horcrux, so unless you know the restoration procedure, you can’t see what’s inside — no need to destroy anything, right?”
Status & feedback
I’ve tested on both Node and React Native and it works, but the React Native side is less battle-tested — bug reports and feedback are welcome.
If this looks useful, a ⭐️ on GitHub would mean a lot!
This content originally appeared on DEV Community and was authored by nchika
nchika | Sciencx (2025-10-07T06:22:48+00:00) horcrux: Split files into encrypted fragments for Node & React Native (TypeScript library). Retrieved from https://www.scien.cx/2025/10/07/horcrux-split-files-into-encrypted-fragments-for-node-react-native-typescript-library/
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