Nodejs Keccak256

by affaan-mef648e01899ba3e8dc6371642deaaf64b4477775No license275K starsListed Oct 9, 2026Updated Oct 9, 2026Repository updated 4 days ago

Prevent Ethereum hashing bugs in JavaScript and TypeScript. Node's sha3-256 is NIST SHA3, not Ethereum Keccak-256, and silently breaks selectors, signatures, storage slots, and address derivation. Use when hashing for Ethereum in JavaScript or TypeScript, or when a selector, signature, storage slot, or derived address is wrong.

Instructions onlySoftware Development

AI-generated overview

Guides JavaScript and TypeScript developers to use Keccak-256 instead of Node's NIST SHA3 for Ethereum hashing.

What it does: This skill explains that Ethereum uses Keccak-256, while Node's crypto.createHash('sha3-256') implements the NIST SHA3 variant, and that the two produce different outputs without warning. It provides code examples for computing hashes, function selectors, event topics, EIP-712 type hashes, storage slots, and addresses using ethers, viem, and web3.js. It also suggests grep commands for auditing a codebase for incorrect sha3 usage.
When to use it: Use it when hashing Ethereum data in JavaScript or TypeScript, such as computing function selectors, event topics, signatures, Merkle trees, or storage slots. It is also relevant when reviewing code that hashes Ethereum data with Node crypto directly, or when a selector, signature, storage slot, or derived address is wrong.
Requirements: No scripts are included; it is instructions and code examples only. Following the examples requires a JavaScript or TypeScript project with a Keccak-aware library such as ethers, viem, or web3.js, and optionally Node's crypto module for comparison.

Node.js Keccak-256

Ethereum uses Keccak-256, not the NIST-standardized SHA3 variant exposed by Node's crypto.createHash('sha3-256').

When to Use

Computing Ethereum function selectors or event topics
Building EIP-712, signature, Merkle, or storage-slot helpers in JS/TS
Reviewing any code that hashes Ethereum data with Node crypto directly

How It Works

The two algorithms produce different outputs for the same input, and Node will not warn you.

javascript

import crypto from 'crypto';import { keccak256, toUtf8Bytes } from 'ethers';
const data = 'hello';const nistSha3 = crypto.createHash('sha3-256').update(data).digest('hex');const keccak = keccak256(toUtf8Bytes(data)).slice(2);
console.log(nistSha3 === keccak); // false

import crypto from 'crypto';import { keccak256, toUtf8Bytes } from 'ethers';
const data = 'hello';const nistSha3 = crypto.createHash('sha3-256').update(data).digest('hex');const keccak = keccak256(toUtf8Bytes(data)).slice(2);
console.log(nistSha3 === keccak); // false

Examples

ethers v6

typescript

import { keccak256, toUtf8Bytes, solidityPackedKeccak256, id } from 'ethers';
const hash = keccak256(new Uint8Array([0x01, 0x02]));const hash2 = keccak256(toUtf8Bytes('hello'));const topic = id('Transfer(address,address,uint256)');const packed = solidityPackedKeccak256(  ['address', 'uint256'],  ['0x742d35Cc6634C0532925a3b8D4C9B569890FaC1c', 100n],);

import { keccak256, toUtf8Bytes, solidityPackedKeccak256, id } from 'ethers';
const hash = keccak256(new Uint8Array([0x01, 0x02]));const hash2 = keccak256(toUtf8Bytes('hello'));const topic = id('Transfer(address,address,uint256)');const packed = solidityPackedKeccak256(  ['address', 'uint256'],  ['0x742d35Cc6634C0532925a3b8D4C9B569890FaC1c', 100n],);

viem

web3.js

javascript

const hash = web3.utils.keccak256('hello');const packed = web3.utils.soliditySha3(  { type: 'address', value: '0x742d35Cc6634C0532925a3b8D4C9B569890FaC1c' },  { type: 'uint256', value: '100' },);

const hash = web3.utils.keccak256('hello');const packed = web3.utils.soliditySha3(  { type: 'address', value: '0x742d35Cc6634C0532925a3b8D4C9B569890FaC1c' },  { type: 'uint256', value: '100' },);

Common patterns

typescript

import { id, keccak256, AbiCoder } from 'ethers';
const selector = id('transfer(address,uint256)').slice(0, 10);const typeHash = keccak256(toUtf8Bytes('Transfer(address from,address to,uint256 value)'));
function getMappingSlot(key: string, mappingSlot: number): string {  return keccak256(    AbiCoder.defaultAbiCoder().encode(['address', 'uint256'], [key, mappingSlot]),  );}

import { id, keccak256, AbiCoder } from 'ethers';
const selector = id('transfer(address,uint256)').slice(0, 10);const typeHash = keccak256(toUtf8Bytes('Transfer(address from,address to,uint256 value)'));
function getMappingSlot(key: string, mappingSlot: number): string {  return keccak256(    AbiCoder.defaultAbiCoder().encode(['address', 'uint256'], [key, mappingSlot]),  );}

Address from public key

typescript

import { keccak256 } from 'ethers';
function pubkeyToAddress(pubkeyBytes: Uint8Array): string {  const hash = keccak256(pubkeyBytes.slice(1));  return '0x' + hash.slice(-40);}

import { keccak256 } from 'ethers';
function pubkeyToAddress(pubkeyBytes: Uint8Array): string {  const hash = keccak256(pubkeyBytes.slice(1));  return '0x' + hash.slice(-40);}

Audit your codebase

bash

grep -rn "createHash.*sha3" --include="*.ts" --include="*.js" --exclude-dir=node_modules .grep -rn "keccak256" --include="*.ts" --include="*.js" . | grep -v node_modules

grep -rn "createHash.*sha3" --include="*.ts" --include="*.js" --exclude-dir=node_modules .grep -rn "keccak256" --include="*.ts" --include="*.js" . | grep -v node_modules

Rule

For Ethereum contexts, never use crypto.createHash('sha3-256'). Use Keccak-aware helpers from ethers, viem, web3, or another explicit Keccak implementation.

Source and attribution

Source:affaan-m/ECCinskills/nodejs-keccak256at commitef648e0

License: No license

Content belongs to its original authors. SourceWeft indexes it from a public repository.

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Nodejs Keccak256

Node.js Keccak-256

When to Use

How It Works

Examples

ethers v6

viem

web3.js

Common patterns

Address from public key

Audit your codebase

Rule

Source and attribution

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