Bitcoin: How to Create and Sign a Segwit Transaction Using Any NPM Package

Creating Segwit Transactions with Bitcore Node: A Troubleshooting Guide

As a Node.js developer, you’ve probably encountered issues using the bitcore-lib package to create and sign Bitcoin transactions. One of the most common challenges is trying to use the Segwit feature introduced in Bitcoin Core 26.1. In this article, we’ll explore how to overcome these limitations and successfully create Segwit transactions using the same NPM package.

The Problem: Legacy Transactions

When creating legacy Bitcoin transactions using bitcore-lib, it appears that they don’t support Segwit by default. This is because the package is based on the old Bitcoin Core protocol, which doesn’t natively support Segwit. However, a few NPM packages have been created to close this gap.

The solution: using bitcore-segwit

To create and sign Segwit transactions using any npm package that supports it, you can use the bitcore-segwit package (available at [ This package provides an easy way to work with Segwit-compatible Bitcoin nodes and wallets.

Step-by-step instructions

Here is a step-by-step guide to creating and signing Segwit transactions with bitcore-lib and bitcore-segwit:

• Install the required packages

  : Run the following command in your terminal:

npm install bitcore libseaweed

• Create a new transaction: Create a new transaction using the newTransaction method provided by libseaweed:

const { Transaction } = require('libseaweed');
const bitcoreLib = require('./bitcore-lib');
// Create a new wallet (e.g. from a private key)
let wallet;
try {
const privateKey = 'your_private_key_here';
wallet = await bitcoreLib.createWallet(privateKey);
} catch(error) {
console.error(error);
}
// Create new transaction
const tx = newtransaction(
wallet.address,
[new BitcoindAddress('1.2.3.4:1234'), // sender address]
);
// Set Segwit flag for transaction
tx.setSegwits([
{ type: 'publicKey', privateKey: privateKey },
]);
// Sign transaction with new private key (or use existing one)
const signature = await bitcoreLib.signTransaction(tx, 'your_new_private_key_here');

In this example:

• We create a wallet with bitcore-lib and store it in the wallet variable.

• We create a new transaction with libseaweed.

• We set the Segwit flag for the transaction by adding an object with two properties: type = 'publicKey' and privateKey = privateKey. This tells libseaweed to use your private key as the public key in the transaction.

• Finally, we sign the transaction with the new private key.

Verify the transaction

To verify that the Segwit transaction was created successfully, you can use the following code:

const { Transaction } = require('libseaweed');
const bitcoreLib = require('./bitcore-lib');
// Create a new wallet (e.g. from a private key)
let wallet;
try {
const privateKey = 'your_private_key_here';
wallet = await bitcoreLib.createWallet(privateKey);
} catch(error) {
console.error(error);
}
// Create new transaction
const tx = newtransaction(
wallet.address,
[new BitcoindAddress('1.2.3.4:1234'), // sender address]
);
// Set Segwit flag for transaction
tx.setSegwits([
{ type: 'publicKey', privateKey: privateKey },
]);
// Sign transaction with new private key (or use existing one)
const signature = await bitcoreLib.signTransaction(tx, 'your_new_private_key_here');
// Verify transaction
const verificationTx = newtransaction(
wallet.address,
tx.hash,
);
await verificationTx.verify(signature);

If the transaction is successfully verified, you will see a message indicating that the transaction has been confirmed.