affaan-m/everything-claude-code/nodejs-keccak256

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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.

Install

npx vskill@latest install affaan-m/everything-claude-code/nodejs-keccak256

SKILL.md

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

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],
);
viem
typescript
import { keccak256, toBytes } from 'viem';
const hash = keccak256(toBytes('hello'));
web3.js
javascript
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]),
  );
}
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);
}
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

Rule

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

Security

  • Security scanPassed, 96 of 100Pattern checks on the skill's files.
  • Model reviewPassed

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Source

Popularity

Repository stars
169,782
Repository forks
26,313
Repository npm downloads, 7 days
1,548
7-day trend score
78

Stars and forks are for the whole GitHub repository, not this skill alone. Downloads are for the repository's npm package. Refreshed 26 Apr 2026, 6 months ago.

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