ethereumjs-util

What is ethereumjs-util?

The ethereumjs-util package provides a set of utility functions for Ethereum. These utilities include functions for handling addresses, big numbers, hashing, and encoding/decoding data according to the Ethereum protocol standards. It is a foundational package that can be used to develop Ethereum-based applications, facilitating tasks such as transaction formatting, signature verification, and data conversion.

What are ethereumjs-util's main functionalities?

Address Formatting

Converts an Ethereum address to its checksummed version to prevent case sensitivity errors.

const { toChecksumAddress } = require('ethereumjs-util');
const checksumAddress = toChecksumAddress('0xfb6916095ca1df60bb79ce92ce3ea74c37c5d359');
console.log(checksumAddress);

Hashing

Generates a keccak256 hash of the input data, a common hashing function used in Ethereum.

const { keccak256 } = require('ethereumjs-util');
const hash = keccak256(Buffer.from('hello'));
console.log('Hash:', hash.toString('hex'));

Signature Verification

Signs a message hash with a private key and serializes the signature in a format compatible with RPC calls.

const { ecsign, toRpcSig } = require('ethereumjs-util');
const privateKey = Buffer.from('c87509a1c067bbde7aebb4d3c0a0b8ab8bd02b676c91662b5f41c4ec9863d8ee', 'hex');
const msgHash = keccak256(Buffer.from('hello'));
const sig = ecsign(msgHash, privateKey);
const serializedSig = toRpcSig(sig.v, sig.r, sig.s);
console.log('Signature:', serializedSig);

Other packages similar to ethereumjs-util

web3

Web3 is a comprehensive Ethereum library that includes utilities similar to ethereumjs-util but also provides a wide range of functionalities to interact with Ethereum nodes directly. It covers the entire Ethereum API and is more extensive for building DApps.

ethers

Ethers is a lightweight library that aims to be a complete and compact library for interacting with the Ethereum Blockchain and its ecosystem. It includes utilities for addresses, big numbers, and hashing, similar to ethereumjs-util, but also features a complete set of functions to interact with smart contracts and blockchain data.

README

SYNOPSIS

or #ethereumjs on freenode

A collection of utility functions for ethereum. It can be used in node.js or can be in the browser with browserify.

API

properties

• MAX_INTEGER - The max integer that the VM can handle
• TWO_POW256 - 2^256
• SHA3_NULL - SHA3-256 hash of null
• SHA3_RLP_ARRAY - SHA3-256 of an RLP of an empty array
• SHA3_RLP - SHA3-256 hash of the RLP of null
• BN
• rlp

methods

zeros(number)

Returns buffer filled with 0's
Parameters

• number - the number of bytes to return

Return: Buffer

pad(val, length)

Pads an Array or Buffer with leading zeros till it has length bytes Parameters

• val - the value to pad
• length - the of the resulting value

Return: Array or Buffer

rpad(val, length)

Pads an Array or Buffer with trailing zeros till it has length bytes Parameters

• val - the value to pad
• length - the of the resulting value

Return: Array or Buffer

unpad(val)

Trims leading zeros from a Buffer or an Array Parameters

• val - a Buffer or an Array to unpad

Return: Buffer or Array

toBuffer(val)

Attempts to turn a value into a Buffer. Attempts to turn a value into a Buffer. Supports Buffer, string, number, null/undefined, BN.js or other objects with a toArray() method.

Parameters

• val the object to be converted

Return: Buffer

intToHex(int)

Converts an Integer into a hex String Parameters

• int

Return: String

intToBuffer(int)

Converts an Integer to a Buffer Parameters

• int

Return: Buffer

bufferToInt(buf)

Converts a Buffer to an Integer Parameters

• buf

Return: Interger

fromSigned(buf)

Interprets a Buffer as a signed Integer Parameters

• buf

Return: BN.js

toUnsigned(num)

Converts a BN.js to an unsigned integer Parameters

• num - a BN.js

Return: buffer

publicToAddress(pubKey)

Returns the ethereum address of a given public key
Parameters

• pubKey - the public key as a Buffer

Return: : Buffer

privateToAddress(privateKey)

Returns the ethereum address of a given private key
Parameters

• privateKey - the private key as a Buffer

Return: Buffer

privateToPublic(privateKey)

Returns the ethereum public key of a given private key Parameters

• privateKey - the private key as a Buffer

Return: Buffer

generateAddress(from, nonce)

Generates an address of a newly created contract. Don't forget to increment the nonce to get the correct address. Parameters

• from - the address of the account creating the contract
• nonce - the creating accounts nonce

Return: Buffer

sha3(a, bytes)

Returns a sha3 of a of the length of bytes
Parameters

• a - the value to hash
• bytes - how many bytes the hash should be

Return: Buffer

sha256(a, bytes)

Returns a sha256 of a Parameters

• a - the value to hash

Return: Buffer

ripemd160(a, bytes)

Returns a ripemd160 of a Parameters

• a - the value to hash
• padded - pad the hash to 256 bits with zeroes

Return: Buffer

rlphash(a)

Returns a sha3 of the RLP encoded version of a Parameters

• a - the value to encode and hash

Return: Buffer

printBA(ba)

Print a Buffer Array
Parameters

• ba - an Array of Buffers

Return: a Buffer Array

baToJSON(ba)

Converts a buffer array to JSON Parameters

• ba - an Array of Buffers

Return: a JSON Object

isHexPrefixed(string)

Returns a Boolean on whether or not the String starts with 0x Parameters

• string - a String

Return: Boolean

stripHexPrefix(string)

Removes 0x from a given String
Parameters

• string - a String

Return: String

addHexPrefix(string)

Adds 0x to a given string if it does not already start with 0x
Parameters

• string - a String

Return: string

defineProperties(self, fields)

Defines properties on a Object. It make the assumption that underlying data is binary. Parameters

• self - the Object to define properties on
• fields - an array fields to define. Fields can contain:
• name the name of the properties
• length the number of bytes the field can have
• allowLess if the field can be less than the length
• allowEmpty

validate(fields, data)

Validate defined fields
Parameters

• fields
• data

Return: Boolean

LICENSE

MPL-2.0