secret-share-{split,combine}

This tool allows for securely splitting and recombining secrets using a secure implementation of the Shamir secret sharing scheme. It is a wrapper around my SSS library.

Usage

You need Rust to build sss-cli from source. When you have installed Rust, you can install these tools using Cargo:

# Install sss-cli
cargo install --git https://github.com/dsprenkels/sss-cli --branch v0.1

# Make 4 shares with recombination threshold 3
echo "Tyler Durden isn't real." | secret-share-split -n 4 -t 3 >shares.txt

# Take the first 3 shares and combine them
head -n 3 shares.txt | secret-share-combine

Note that after this installation, you need to add Cargo's installation directory to your $PATH if you don't have it there yet.

To uninstall the crate you can use a command similar to the install-command above.

# Uninstall the secret sharing tools
cargo uninstall shamirsecretsharing-cli

macOS

To install on macOS system, you can also use Homebrew package manager. The package is not yet in the upstream homebrew-core, but there exists a tap with sss-cli formula here.

To install using Homebrew, run: brew install vitkabele/tap/sss-cli.

F.A.Q.

Why are the shares so much longer than the secrets?

This Shamir secret sharing library could produce shares that are shorter than their current length. However, while Shamir secret sharing is secure for confidentiality, this is not the case for integrity. An attacker could tamper with some of the shares. After restoring the (malicious) secret, you would not be able to know that it has been tampered with. sss-cli uses an AEAD wrapper so that the shares cannot be tampered with, which takes up some extra space.

Changelog

New in version 0.1.2

• Use the RustCrypto crypto-secretbox crate instead of xsalsa20poly1305 (#12).

Questions

Feel free to open an issue or send me an email on my Github associated e-mail address.