Your Secrets, Distributed.

Securely split sensitive data into self-contained HTML "parts." Losing one doesn't matter. Stealing one is useless. Only you and your threshold of parts can bring the secret back to life.

Split a Secret How it Works
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Project Context & Motivation

This project was motivated by the the Hacker News discussion "Horcrux: Split your file into encrypted fragments" and the desire to create a more self contained and practical implementation of the same concept for personal use.

The goal was for this tool to work on any platform and require no dependencies (other than a web browser), and be future-proof enough to be usable decades from now. An excellent similar tool was created by Ian Coleman (https://iancoleman.io/shamir/) which heavily inspired this project, this iteration adds more features such as self-contained parts and optional password protection.

How to Use

The entire process executes locally within your browser's memory.

Step 1 Input Schematic
1

Input Locally

Paste your secret (text, seed phrase, password) into the browser. It never leaves your device.

Step 2 Split Schematic
2

Set Thresholds

Define the total number of parts and the minimum required to recover. E.g., "3 of 5".

Step 3 Distribute Schematic
3

Download & Scatter

Get individual HTML files. Store them on USBs, different cloud services, or share them with trusted contacts.

Step 4 Recovery Schematic
4

Reassemble Anywhere

Open any single part file in a browser. Paste in the remaining required parts to unlock the secret.

01. The Algorithm

This tool utilizes Shamir's Secret Sharing to split data into unique parts. This algorithm provides Information-Theoretic Security, meaning that even with infinite computing power, an attacker with fewer than the required parts can never reconstruct the secret.

The core logic is based on the proven, open-source secrets.js implementation, which was security audited in 2019.

02. Fully self-contained

All the "parts" generated by the split tool are fully self-contained HTML files with an embedded combiner tool and work fully offline*.

This means that to recover a secret, all you will ever need is a standard web browser and the required parts. The combiner tool only uses standard JavaScript, the DOM API as well as the Web Crypto API, which provides long term compatibility and make the parts future-proof**.

* NOTE: The combiner tool can also be used a as fully offline, self-contained tool by simply saving the HTML page.

** In the very unlikely event that a self-contained part becomes incompatible or doesn't work, an independent combiner tool written in a different programming language (Python) is available in the GitHub Repository to recover the secret.

Practical Applications

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Digital Inheritance

Distribute shares of your master password to family members. No one can access your accounts alone, but they can recover access together if you are incapacitated.

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Geographic Redundancy

Split your primary email recovery code. Store shares in different physical locations (home, office, safe) to ensure a single fire or burglary doesn't lock you out.

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Collaborative Custody

Protect sensitive family documents by requiring a "quorum" of trusted friends to unlock them. This ensures that no single person holds the power of access.

Frequently Asked Questions

What happens if I lose one of the parts?

As long as you still have the minimum number of parts (your threshold k), you can fully recover your secret. If you fall below that number, the secret is mathematically impossible to recover.

Are individual parts "encrypted"?

No, and they don't need to. The individual parts are secure by design because they are mathematically incomplete.

Unless someone possesses the minimum number of parts you specified (the threshold), the individual shares they hold are effectively random noise. They contain zero information about your original secret, making it impossible to "crack" or guess. You can store these files on a USB drive, in the cloud, or on paper without needing any additional encryption or passwords.

Can I use any browsers for splitting and combining?

Yes. The self-contained HTML files use standard JavaScript. You can generate them in Chrome on a Mac and reconstruct them in Firefox on Linux. No internet connection is required.

Why is there the option to password-protect the secret when encryption is not needed?

This option allows to add a second layer of security if needed.

The individual parts cannot be deciphered whether a password is used or not. However, as soon as the minimum number of parts is gathered, the secret can be reconstructed.

By adding a password, even if an attacker manages to collect enough parts, they would still need to know the password to access the original secret.

Is there a limit to how large the secret can be?

While there is no hard mathematical limit, extremely large secrets will result in very large HTML files and may slow down your browser's RAM during the splitting process. It is ideal for text up to 50KB (approx. 10,000 words).