shamirs-secret-sharing

A simple implementation of Shamir's Secret Sharing configured to use a finite field in GF(2^8) with 128 bit padding.

Preface

Much of what you see in this module has been ported from or directly influenced by secrets.js, c-sss, and libgfshare

Installation

$ npm install shamirs-secret-sharing

Example Usage (Node.js)

import sss from 'shamirs-secret-sharing'

const secret = Buffer.from('secret key')
const shares = sss.split(secret, { shares: 10, threshold: 4 })
const recovered = sss.combine(shares.slice(3, 7))

console.log(recovered.toString()) // 'secret key'

Example Usage (Socket Runtime)

Configure the [build.copy-map] section in socket.ini:

[build.copy-map]
node_modules/shamirs-secret-sharing = shares-secret-sharing

import Buffer form 'socket:buffer'
import combine from '/shares-secret-sharing/combine.js'
import split from '/shares-secret-sharing/split.js'

const secret = Buffer.from('secret key')
const shares = sss.split(secret, { shares: 10, threshold: 4 })
const recovered = sss.combine(shares.slice(3, 7))

console.log(recovered.toString()) // 'secret key'

API

shares = sss.split(secret, opts)

Generate a set of unique and distinct shares for a secret with a configured threshold.

• secret (required) - A Buffer instance or string that represents a secret for which shares are created for
• opts (required) - An object of options for configuring how shares are created for a secret
  • opts.shares (required) - The number of n shares that should be created for this secret
  • opts.threshold (required) - The number of t of n distinct share that are required to reconstruct this secret
  • opts.random (optional) - An optional Pseudorandom number generator (PRNG) function that should generate a random value buffer based on some input. e.g opts.random = (size) => randomBytes(size)

secret = sss.combine(shares)

Reconstruct a secret from a distinct set of shares. This function will not throw an error for incorrect shares or if p(0) is not the correct secret for the given shares.

• shares (required) - An array of shares, that is an array of equally sized and distinct Buffer instances, or strings

See Also

• https://en.wikipedia.org/wiki/Shamir%27s_Secret_Sharing
• https://en.wikipedia.org/wiki/Secret_sharing
• https://en.wikipedia.org/wiki/Lagrange_polynomial
• https://en.wikipedia.org/wiki/Horner%27s_method
• https://en.wikipedia.org/wiki/Pseudorandom_number_generator
• https://codesandbox.io/s/shamirs-secret-sharing-pcsbk

License

MIT