SKILL.md
$27
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
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
import { keccak256, toBytes } from 'viem';
const hash = keccak256(toBytes('hello'));
### web3.js
const hash = web3.utils.keccak256('hello');
const packed = web3.utils.soliditySha3(
{ type: 'address', value: '0x742d35Cc6634C0532925a3b8D4C9B569890FaC1c' },
{ type: 'uint256', value: '100' },
);
### Common patterns
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
import { keccak256 } from 'ethers';
function pubkeyToAddress(pubkeyBytes: Uint8Array): string {
const hash = keccak256(pubkeyBytes.slice(1));
return '0x' + hash.slice(-40);
}
### Audit your codebase
grep -rn "createHash.sha3" --include=".ts" --include="*.js" --exclude-dir=node_modules .
grep -rn "keccak256" --include=".ts" --include=".js" . | grep -v node_modules