secret-sharing

A CLI tool for creating n secret shares of data and combining exactly k of those shares to recover the data. The process for creating shares is as follows:

1. Compress the secret data using Zstandard
2. Create a 32-byte secret key using OsRng
3. Encrypt the compressed secret using the ChaCha20-Poly1305 algorithm, with the secret key and a nonce of zero
4. Create n 113-byte shares of the secret key (followed by 32 bytes of zeroes to pad it up to 64 bytes) using Shamir Secret Sharing
5. Each secret key share is prepended to the encrypted payload

Installation

cargo install --git https://github.com/theodus/secret-sharing

Example Usage

• secret-sharing create 3 2 <data.txt produces 3 secret shares of the content of data.txt, where 2 of the shares are required to recover the content of data.txt
• secret-sharing combine <share1.hex <share2.hex recovers 2 shares into the secret data, assuming the shares were created with k=2