How do I derive new Accounts from xPub?

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]

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.
}

[vzelenko]

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