nodejs-keccak256
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.
- Kind
- Skill
- Works with
- Claude Code, Codex
- Languages
- TypeScript / JavaScript
- Source
- affaan-m/ECC @ d3b8a3e90890
- Path
- skills/nodejs-keccak256/SKILL.md
- License
- MIT
- Jobs
- Debugging
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# 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
…