Keccak-256 Hash Calculator
Keccak-256 Hash Function
What is Keccak-256?
Keccak-256 is the hash function used by Ethereum. It's based on the SHA-3 standard but differs from the finalized SHA-3 specification. Ethereum uses the original Keccak algorithm that was submitted to the NIST competition.
⚠️ Keccak vs SHA-3:
Keccak-256 (used by Ethereum) ≠ SHA3-256 (NIST standard). They produce different outputs! Ethereum uses the original Keccak before NIST made changes.
Ethereum Use Cases:
- Address Generation: Public key → Keccak-256 → address
- Function Signatures: First 4 bytes of Keccak hash
- Event Topics: Event signature hashing
- Storage Keys: Mapping key hashing
- Transaction Hashes: Unique transaction identifiers
Example: Ethereum Address Generation
1. Public Key: 04abc123...def789 (65 bytes)
2. Keccak-256 Hash: c5d2460186f7233c927e7db2dcc703c0e500b653ca82273b7bfad8045d85a470
3. Take last 20 bytes: 0x...ad8045d85a470
4. Add 0x prefix: 0x742d35Cc6634C0532925a3b844Bc9e7595f0bEb
Example: Function Selector
Function: transfer(address,uint256)
Keccak-256: a9059cbb2ab09eb219583f4a59a5d0623ade346d962bcd4e46b11da047c9049b
First 4 bytes: 0xa9059cbb
This becomes the function selector in the transaction data
How to Calculate (JavaScript):
// Using ethers.js
import { keccak256, toUtf8Bytes } from 'ethers';
const hash = keccak256(toUtf8Bytes('Hello'));
// Using keccak package
import { keccak256 } from 'keccak';
const hash = keccak256(Buffer.from('Hello')).toString('hex');💡 Key Differences from SHA-256:
- Ethereum uses Keccak-256 (not SHA3-256)
- Bitcoin uses SHA-256 (different algorithm)
- Keccak was selected as SHA-3 winner in 2012
- NIST made changes before standardizing as SHA-3 in 2015
- Ethereum had already adopted original Keccak by then
- Both produce 256-bit (64 hex character) hashes
🔧 Implementation Note:
True Keccak-256 calculation requires a specialized library. This calculator demonstrates the concept. For production use, install packages like:
ethers.jsorviem(for Ethereum development)keccakorjs-sha3(standalone hashing)
See Also
Other calculators in Blockchain & Crypto