Ethash - Ethereum's Former Mining Algorithm
Explore the algorithm that powered Ethereum mining before the transition to Proof-of-Stake
In real mining, miners would try millions of nonces seeking a hash below a target difficulty.
Note: This is a simplified demonstration. Actual Ethash involves DAG generation and memory-hard calculations.
What is Ethash?
Ethash was the Proof-of-Work (PoW) consensus algorithm used by Ethereum before its transition to Proof-of-Stake in September 2022 (The Merge). It was specifically designed to be ASIC-resistant, meaning it aimed to prevent specialized mining hardware from dominating the network, keeping mining more accessible to general users with GPUs.
Historical Note: While Ethash is no longer used on the Ethereum mainnet after The Merge, it remains an important part of Ethereum's history and is still used by some Ethereum-based networks that continue to use Proof-of-Work.
How Ethash Works
Key Components
- Directed Acyclic Graph (DAG) - A large dataset regenerated every 30,000 blocks (about 5 days)
- Keccak-256 - Used as the core hash function within the algorithm
- Memory-Hard Computation - Requires significant memory access, benefiting GPUs over ASICs
- Nonce Search - Miners try different nonce values to find a hash below the target difficulty
The Mining Process
- DAG Generation - A large dataset (1-4GB) is created based on the block number
- Header Hash - A Keccak-256 hash of the block header (without nonce) is computed
- Mix Creation - The header hash is combined with the nonce to create a "mix"
- DAG Lookups - The algorithm performs multiple pseudo-random lookups in the DAG
- Final Hash - After processing, a final hash is computed and compared against the difficulty target
- Mining Success - If the hash is below the target, the block is successfully mined
Ethash Design Goals
ASIC Resistance
- Memory-hard operations favor GPUs
- DAG size increases over time
- Promotes mining decentralization
- Allows consumer hardware to participate
Light Client Verification
- Enables quick verification without full DAG
- Supports mobile and lightweight devices
- Uses a smaller cache instead of full dataset
- Maintains security while reducing resource needs
Ethash vs. Other Mining Algorithms
| Feature | Ethash (Ethereum) | SHA-256 (Bitcoin) | Scrypt (Litecoin) |
|---|---|---|---|
| ASIC Resistance | High (memory-hard) | None (ASIC dominated) | Moderate (memory-hard) |
| Memory Requirements | Very High (GB scale) | Low | High (MB scale) |
| Verification Complexity | Light client friendly | Simple verification | Moderate |
| Energy Efficiency | Medium | Low | Medium |
The Transition to Proof-of-Stake
In September 2022, Ethereum completed "The Merge" - a historic transition from Proof-of-Work (using Ethash) to Proof-of-Stake. This change was made for several reasons:
- Energy Efficiency - Reducing Ethereum's energy consumption by ~99.95%
- Lower Barrier to Participation - Allowing more people to help secure the network
- Better Scalability - Preparing the foundation for future scaling upgrades
- Reduced Issuance - Decreasing the rate of new ETH creation
Legacy and Continued Use
While Ethereum has moved on from Ethash, the algorithm continues to be used in:
- Ethereum Classic (ETC) - A continuation of the original Ethereum blockchain
- Other Ethereum-based Networks - Several smaller blockchains that forked from Ethereum
- Academic Research - Studying memory-hard functions and mining algorithm design
About This Demonstration
The interactive tool above provides a simplified illustration of Ethash. In reality, the algorithm is much more complex, involving:
- A multi-gigabyte DAG that grows over time
- Complex mixing operations not practical to run in a browser
- Memory-hard functions designed to require significant RAM
This demonstration uses Keccak-256 as the base (which Ethash uses internally) to give you a feel for how changing the nonce affects the output hash.