shamir-tss-gf256
v0.5.0
Published
Uses Shamir's secret sharing method to allows space-effecient secret sharing (splitting) that requires a minimum threshold of shares in order to unlock the orignal secret.
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Shamir Threshold Secret Sharing using Galois Field 2^8
Uses Shamir's secret sharing method to allows space-efficient secret sharing (splitting) requiring a minimum threshold of shares in order to unlock the original secret.
- Wikipedia on Shamir's Secret Sharing
- Octect-based Shamir Secret Sharing patterned after IETF informational draft Threshold Secret Sharing
- The Laws of Cryptography
Example
import * as shamir_tss from 'shamir-tss-gf256'
// or const shamir_tss = require('shamir-tss-gf256')
// or <script src='https://unpkg.com/[email protected]/umd/shamir-tss-gf256.min.js' ></script>
const secret = shamir_tss.randomBytes(16) // or any Uint8Array/Buffer
// split into 10 shares, allowing any 3 to unlock the secret
const shares = shamir_tss.generateShares_b64(secret, 3, 10)
// shares = [
// 'AwH9nHA-35qs4JvF8qkfngTK',
// 'AwI3E71t-b3c2odZ_2pNcT-3',
// 'AwO1ZJY6wtOKODOfme1m1wP0',
// 'AwSoWHr_aQSotSWu6Pl60tEj',
// 'AwUqL1GoUmr-V5Fojn5RdO1g',
// 'AwbgoJz7dE2ObY30g70Dm9Yd',
// 'Awdi17esTyPYjzky5TooPepe',
// 'AwjN7ewQD5wmByQm8vxuDECz',
// 'AwlPmsdHNPJw5ZDglHtFqnzw',
// 'AwqFFQoUEtUA34x8mbgXRUeN' ]
const res_under_a = shamir_tss.unlockShares([shares[2], shares[7]], false)
// res_under_a = false
try {
const res_under = shamir_tss.unlockShares([shares[2], shares[7]])
} catch (err) {
// Number of shares did not meet threshold to unlock shared secret. (2 of 3, 0 duplicates)
}
const res_min = shamir_tss.unlockShares([shares[2], shares[7], shares[4]])
// res_min = Uint8Array [ 127, 235, 91, 105, 228, 244, 250, 2, 47, 3, 148, 46, 52, 56, 56, 137 ]
const res_over = shamir_tss.unlockShares([shares[2], shares[7], shares[4], shares[9], shares[1]])
// res_over = Uint8Array [ 127, 235, 91, 105, 228, 244, 250, 2, 47, 3, 148, 46, 52, 56, 56, 137 ]
API
Primary
generateShares(secret, thresholdShares, totalShares)
Transforms secret
into a Galois Field polynomial according to Shamir's secret
sharing method, returning the specified number of totalShares
where any
unique subset of thresholdShare
shares will unlock the original secret
.
Returns the shares
as array of Uint8Array
.
generatorShares(secret, thresholdShares, [totalShares])
generateShares()
returning an iterator of Uint8Array
shares
.
unlockShares(shares, [valueIfUnderThreshold])
Computes and returns the secret
using provided shares
array, given
sufficient number of shares. Otherwise, valueIfUnderThreshold
is returned.
Cautionary Note: There are no self-consistency checks built into Shamir Threshold Secret Shares -- combining shares from different source will result in unlocking some undefined "secret".
generateShares_b64(secret, thresholdShares, totalShares)
generateShares()
returning an array of Base64 encoded shares
.
generatorShares_b64(secret, thresholdShares, [totalShares])
generateShares()
returning an iterator of Base64 encoded shares
.
unlockShares_b64(shares, [valueIfUnderThreshold])
unlockShares()
with result Base64 encoded.
Utilities
isBinarySecret(arg)
True if arg
is a Buffer
or Uint8Array
, false otherwise.
randomBytes(n_bytes)
In Browser environments, generates a Uint8Array
of specified byte length using crypto.getRandomValues()
.
In NodeJS, generates a Uint8Array
of specified byte length using crypto.randomBytes()
.
u8_to_base64(u8)
Converts a Uint8Array
or Buffer
to a Base64 (URL safe) encoded string.
base64_to_u8(string_b64)
Converts a Base64 encoded string to a Uint8Array
or Buffer
.
Internal API
The internal class ShamirSecretShare
(alias ShamirTSS
) is exposed. Please
read the source for understanding and details.
Galois Field 256 (2^8) math primitives
function compute_poly(x, poly_coeff) {}
function lagrange_basis_poly_at_zero(u) {}
function lagrange_interpolate(u, v_iterable) {}
function add(x, y) {}
function mul(x, y) {}
function div(x, y) {}
To use:
const gf256 = require('shamir-tss-gf256/cjs/gf256')
// or import * as gf256 from 'shamir-tss-gf256/esm/gf256'
// or <script src='https://unpkg.com/[email protected]/umd/gf256.js' ></script>