eth-hash: Ethereum Keccak256 Hashing Function

0.8.0 · active · verified Thu Apr 09

eth-hash is a low-level Python library that provides the Ethereum hashing function, Keccak256. While sometimes erroneously referred to as SHA3, it implements the specific Keccak variant used in Ethereum. It is primarily intended for internal use by other Ethereum development tools. The current version is 0.8.0, with releases driven by the needs of the broader Ethereum ecosystem.

Warnings

gotcha Ethereum's hashing algorithm is Keccak256, not SHA3. While often colloquially referred to as SHA3, it is a distinct function. Using libraries or functions explicitly named 'SHA3' might lead to incorrect hash values for Ethereum contexts.
Fix: Always refer to and use functions explicitly implementing 'Keccak256' for Ethereum compatibility. `eth-hash` correctly implements Keccak256.
breaking The `eth-hash` library requires a backend to be installed for the `keccak` function to be available. Installing just `eth-hash` will not provide the hashing functionality out-of-the-box.
Fix: Install `eth-hash` with a chosen backend as an extra, e.g., `pip install "eth-hash[pycryptodome]"` or `pip install "eth-hash[pysha3]"`. `pycryptodome` is generally recommended for its performance and broader compatibility.
gotcha eth-hash is a low-level utility. If you're looking for a more convenient and feature-rich hashing tool that integrates with other Ethereum utilities, `eth_utils.keccak()` is often a friendlier alternative built on top of `eth-hash`.
Fix: Consider using `from eth_utils import keccak` if you need a higher-level API or other Ethereum-related utilities, otherwise `eth-hash` is appropriate for direct Keccak256 operations.

Install

pip install "eth-hash[pycryptodome]" Recommended installation with backend
pip install eth-hash Basic installation (requires manual backend setup)

Imports

keccak
```
from eth_hash.auto import keccak
```
Automatically loads an available backend to provide the keccak256 hashing function.
Keccak256
```
from eth_hash import Keccak256
from eth_hash.backends import pysha3
keccak = Keccak256(pysha3)
```
For explicit backend selection or creating a Keccak256 instance. Avoid using 'SHA3' as it's a different function; Ethereum uses 'Keccak256'.

Quickstart

Demonstrates how to compute a Keccak256 hash using the automatically selected backend, both for a single input and incrementally. The output is a bytes object, which can be converted to a hexadecimal string for display.

from eth_hash.auto import keccak

# Hash a byte string
data_to_hash = b'hello world'
hashed_data = keccak(data_to_hash)
print(f"Hashed data: {hashed_data.hex()}")

# Incremental hashing
preimage = keccak.new(b'part-a')
preimage.update(b'part-b')
incremental_hash = preimage.digest()
print(f"Incremental hash: {incremental_hash.hex()}")

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