ethereumjs-tx

What is ethereumjs-tx?

The ethereumjs-tx package is a JavaScript library for creating, signing, and serializing Ethereum transactions. It is part of the ethereumjs suite of tools and is widely used for interacting with the Ethereum blockchain at a low level.

What are ethereumjs-tx's main functionalities?

Creating a Transaction

This feature allows you to create a new Ethereum transaction by specifying parameters such as nonce, gas price, gas limit, recipient address, value, and data.

const Tx = require('ethereumjs-tx').Transaction;
const txParams = {
  nonce: '0x00',
  gasPrice: '0x09184e72a000',
  gasLimit: '0x2710',
  to: '0x0000000000000000000000000000000000000000',
  value: '0x00',
  data: '0x00',
};
const tx = new Tx(txParams);

Signing a Transaction

This feature allows you to sign a transaction using a private key. The transaction must be signed before it can be sent to the Ethereum network.

const privateKey = Buffer.from('your_private_key', 'hex');
tx.sign(privateKey);

Serializing a Transaction

This feature allows you to serialize a signed transaction into a format that can be sent over the network. The serialized transaction is typically represented as a hexadecimal string.

const serializedTx = tx.serialize();
console.log(serializedTx.toString('hex'));

Other packages similar to ethereumjs-tx

web3

Web3.js is a comprehensive library for interacting with the Ethereum blockchain. It provides higher-level abstractions for sending transactions, interacting with smart contracts, and querying blockchain data. Unlike ethereumjs-tx, which focuses on low-level transaction creation and signing, Web3.js offers a broader range of functionalities.

ethers

Ethers.js is a lightweight library for interacting with the Ethereum blockchain. It provides utilities for creating and signing transactions, interacting with smart contracts, and querying blockchain data. Ethers.js is known for its simplicity and ease of use, making it a popular alternative to ethereumjs-tx for developers who prefer a more streamlined API.

eth-lib

Eth-lib is a low-level library for Ethereum that provides utilities for creating and signing transactions, encoding and decoding data, and working with cryptographic primitives. It is similar to ethereumjs-tx in that it focuses on low-level operations, but it also includes additional utilities for working with Ethereum data structures.

README

SYNOPSIS

A simple module for creating, manipulating and signing Ethereum transactions.

CONTACT

Scrollback or #ethereumjs on freenode

INSTALL

npm install ethereumjs-tx

USAGE

• example

var Tx = require('ethereumjs-tx');
var privateKey = new Buffer('e331b6d69882b4cb4ea581d88e0b604039a3de5967688d3dcffdd2270c0fd109', 'hex');

var rawTx = {
  nonce: '00',
  gasPrice: '09184e72a000', 
  gasLimit: '2710',
  to: '0000000000000000000000000000000000000000', 
  value: '00', 
  data: '7f7465737432000000000000000000000000000000000000000000000000000000600057'
};

var tx = new Tx(rawTx);
tx.sign(privateKey);

var serializedTx = tx.serialize();

BOWSER

For standalone use in the browser inculde ./dist/ethereumjs-tx.js
This will give you a gobal varible EthTx to use. It will also create the globals Buffer and ethUtil
To build for standalone use in the browser install browserify and run npm run build.

API

• new Transaction([data])
• Transaction Properties
• Transaction Methods
• transaction.serialize()
• transaction.hash([signature])
• transaction.sign(privateKey)
• transaction.getSenderAddress()
• transaction.getSenderPublicKey()
• transaction.validate()
• transaction.validateSignature()
• transaction.getDataFee()
• transaction.getBaseFee()
• transaction.getUpfrontCost()
• transaction.toJSON([object])

new Transaction([data])

Creates a new transaction object

• data - a transaction can be initiailized with either a buffer containing the RLP serialized transaction or an array of buffers relating to each of the tx Properties, listed in order below. For example.

var rawTx = {
  nonce: '00',
  gasPrice: '09184e72a000', 
  gasLimit: '2710',
  to: '0000000000000000000000000000000000000000', 
  value: '00', 
  data: '7f7465737432000000000000000000000000000000000000000000000000000000600057',
  v: '1c', 
  r: '5e1d3a76fbf824220eafc8c79ad578ad2b67d01b0c2425eb1f1347e8f50882ab',
  s '5bd428537f05f9830e93792f90ea6a3e2d1ee84952dd96edbae9f658f831ab13'
};

var tx = new Transaction(rawTx);

Or lastly an Object containing the Properties of the transaction like in the Usage example

For Object and Arrays each of the elements can either be a Buffer, hex String , Number, or an object with a toBuffer method such as Bignum

transaction Properties

• raw - The raw rlp decoded transaction.
• nonce
• to - the to address
• value - the amount of ether sent
• data - this will contain the data of the message or the init of a contract.
• v - EC signature parameter
• r - EC signature parameter
• s - EC recovery ID

---

Transaction Methods

transaction.serialize()

Returns the RLP serialization of the transaction
Return: 32 Byte Buffer

---

transaction.hash([signature])

Returns the SHA3-256 hash of the rlp transaction
Parameters

• signature - a Boolean determining if to include the signature components of the transaction. Defaults to true.

Return: 32 Byte Buffer

---

transaction.sign(privateKey)

Signs the transaction with the given privateKey.
Parameters

• privateKey - a 32 Byte Buffer

---

transaction.getSenderAddress()

Returns the senders address
Return: 20 Byte Buffer

---

transaction.getSenderPublicKey()

returns the public key of the sender
Return: Buffer

---

transaction.validate()

Determines if the transaction is schematicly valid by checking its signature and gasCost.
Return: Boolean

---

transaction.validateSignature()

Determines if the signature is valid
Return: Boolean

---

transaction.getDataFee()

Returns the amount of gas to be paid for the data in this transaction
Return: bn.js

---

transaction.getBaseFee()

Returns the minimum amount of gas the tx must have (DataFee + TxFee)
Return: bn.js

---

transaction.getUpfrontCost()

The total amount needed in the account of the sender for the transaction to be valid
Return: bn.js

---

transaction.toJSON([object])

Returns transaction as JSON
Parameters

• object - a Boolean that defaults to false. If object is true then this will return an object else it will return an array

Return: Object or Array

TESTS

test uses mocha. To run
npm test

LICENSE

MPL-2.0