shamirs-secret-sharing-ts/dist/combine.js

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

"use strict";
Object.defineProperty(exports, "__esModule", { value: true });
const constants_1 = require("./constants");
const lagrange_1 = require("./lagrange");
const share_1 = require("./share");
const codec = require("./codec");
/**
 * Reconstruct a secret from a distinct set of shares.
 * @public
 * @param {Array<String|Buffer>} shares
 * @return {Buffer}
 */
function combine(shares) {
    const chunks = [];
    const x = [];
    const y = [];
    const t = shares.length;
    for (let i = 0; i < t; ++i) {
        const share = share_1.parse(shares[i]);
        if (-1 === x.indexOf(share.id)) {
            x.push(share.id);
            const bin = codec.bin(share.data, 16);
            const parts = codec.split(bin, 0, 2);
            for (let j = 0; j < parts.length; ++j) {
                if (!y[j]) {
                    y[j] = [];
                }
                y[j][x.length - 1] = parts[j];
            }
        }
    }
    for (let i = 0; i < y.length; ++i) {
        const p = lagrange_1.lagrange(0, [x, y[i]]);
        chunks.unshift(codec.pad(p.toString(2)));
    }
    const string = chunks.join('');
    const bin = string.slice(1 + string.indexOf('1')); // >= 0
    const hex = codec.hex(bin, constants_1.BIN_ENCODING);
    const value = codec.decode(hex);
    return Buffer.from(value);
}
exports.combine = combine;