dervice-45-copay.js

/**
 * FOR COPAY WALLET
 * Converts multisig xpubs into addresses
 *
 * Dependencies:
 * npm install bitcore
 * 
 * NOTE: You can retrieve xpubs from copay using JSON backup
 * Decrypt json backup using sjcl @ https://github.com/bitwiseshiftleft/sjcl
 */

var bitcore = require('bitcore');

// For 2-of-3 multisig, you need all 3 xpubs
var pubkeys = [
    // List xpubs for all singers here
];

// Number of signers required
var signers = 1;

var keys = [];
for (var x in pubkeys) {
    var parent = new bitcore.HDPublicKey(pubkeys[x]);

    // WTF COPAY? Why use 2147483647?
    // Spent hours trying to figure this out
    // Finally discovered the solution in bitcore-wallet-serivce : lib/model/addressmanager.js
    // Stored as SHARED_INDEX = 0x80000000 - 1
    // Again... WTF. BIP45 says to use m/<cosigner>/0/0,
    // so this should be m/0/0/0 and m/1/0/0 for the first 2 addresses
    var key = parent.derive('m/2147483647/0/0').publicKey;
    keys.push(key);
}

var address = new bitcore.Address(keys, signers, 'livenet');

// Verify first address to confirm proper derivation
console.log('First Address: ', address.toString());