How do I derive new Accounts from xPub?

[vzelenko]

I am trying to derive a new address based on xPub key on Testnet.

const rootKey = bitcoin.HDNode.fromBase58(WALLET_XPUB_KEY, bitcoin.networks.testnet).neutered();
const key = { accountNumber: 20, lastAddressNumber: 10 };
const txtPath = `m/49'/1'/${key.accountNumber}'/0/${key.lastAddressNumber}`;
const child = rootKey.derivePath(txtPath);
return child.getAddress();

It fails on derivePath with message Error: Not a master node - what is the correct way of getting N'th account addresses?

[dabura667]

You can’t derive hardened paths with the xpub alone. You need the private xprv.

[dcousens]

Error: Not a master node means exactly the Error message.
You can only derive m/ paths from a master node.

If you don't need m/, drop the m/.

Additionally, as pointed out by @dabura667, to derive hardened paths you need the private key.

[vzelenko]

@dabura667 & @dcousens - please excuse my ignorance and thank you both for answering! I still do NOT understand HOW to alter the Account digit on the hardened path during the derivation, private or public based. Where can I learn more about it?

[dabura667]

function getBIP44AccountXPub(xprv, accountNumber) {
  const rootKey = bitcoin.HDNode.fromBase58(xprv, bitcoin.networks.testnet);
  const txtPath = `m/44'/1'/${accountNumber}'`;
  const child = rootKey.derivePath(txtPath);
  return child.neutered().toBase58(); // returns xpub
}

function xPubToAddress(xpub, index, isChange) {
  if (isChange === undefined) isChange = 0
  else isChange = 1

  if (index === undefined) index = 0

  if (xpub === undefined) throw new Error('Need xpub')

  const accountRootKey = bitcoin.HDNode.fromBase58(xpub, bitcoin.networks.testnet);
  const txtPath = `${isChange}/${index}`;
  const child = accountRootKey.derivePath(txtPath);
  return child.keyPair.getAddress();
  // Note: getAddress() only returns a non-segwit address that starts with a 1 (or m/n in testnet)
  // So to generate BIP49 addresses (P2WPKH-in-P2SH) you need to manually hash the public key
  // and generate the scripts to hash for the P2SH.
}

[dabura667]

You can find out how to generate the BIP49 addresses here:

bitcoinjs-lib/test/integration/bip32.js

Lines 66 to 81 in fdcd7aa

	it('can create a BIP49, bitcoin testnet, account 0, external address', function () {
	var mnemonic = 'abandon abandon abandon abandon abandon abandon abandon abandon abandon abandon abandon about'
	var seed = bip39.mnemonicToSeed(mnemonic)
	var root = bitcoin.HDNode.fromSeedBuffer(seed)
	var path = "m/49'/1'/0'/0/0"
	var child = root.derivePath(path)
	var keyhash = bitcoin.crypto.hash160(child.getPublicKeyBuffer())
	var scriptSig = bitcoin.script.witnessPubKeyHash.output.encode(keyhash)
	var addressBytes = bitcoin.crypto.hash160(scriptSig)
	var outputScript = bitcoin.script.scriptHash.output.encode(addressBytes)
	var address = bitcoin.address.fromOutputScript(outputScript, bitcoin.networks.testnet)
	assert.equal(address, '2Mww8dCYPUpKHofjgcXcBCEGmniw9CoaiD2')
	})

[vzelenko]

Thank you!

…

On Feb 17, 2018, at 22:18, Dabura667 ***@***.***> wrote: function getBIP44AccountXPub(xprv, accountNumber) { const rootKey = bitcoin.HDNode.fromBase58(xprv, bitcoin.networks.testnet); const txtPath = `m/44'/1'/${accountNumber}'`; const child = rootKey.derivePath(txtPath); return child.toBase58(); // returns xpub } function xPubToAddress(xpub, index, isChange) { if (isChange === undefined) isChange = 0 else isChange = 1 if (index === undefined) index = 0 if (xpub === undefined) throw new Error('Need xpub') const accountRootKey = bitcoin.HDNode.fromBase58(xpub, bitcoin.networks.testnet); const txtPath = `${isChange}/${index}`; const child = accountRootKey.derivePath(txtPath); return child.keyPair.getAddress(); // Note: getAddress() only returns a non-segwit address that starts with a 1 (or m/n in testnet) // So to generate BIP49 addresses (P2WPKH-in-P2SH) you need to manually hash the public key // and generate the scripts to hash for the P2SH. } — You are receiving this because you authored the thread. Reply to this email directly, view it on GitHub, or mute the thread.

[dcousens]

@vzelenko could you help us improve this example to help others in future?

[vzelenko]

I'd be happy to give it a shot today/tomorrow.