ETH_HASH(1)

NAME
eth_hash - eth-hash Documentation

The Ethereum hashing function, keccak256, sometimes (erroneously) called sha3

INSTALLATION

    python -m pip install eth-hash

  Quickstart

  Choose a hashing backend

If you're not sure, choose "pycryptodome" because it supports pypy3.

You can find a full list of each currently supported backend in eth_hash.backends.

  Install

Put the backend you would like to use in brackets during install, like:

    python -m pip install "eth-hash[pycryptodome]"

  Compute a Keccak256 Hash

    >>> from eth_hash.auto import keccak
    >>> keccak(b'')
    b"\xc5\xd2F\x01\x86\xf7#<\x92~}\xb2\xdc\xc7\x03\xc0\xe5\x00\xb6S\xca\x82';{\xfa\xd8\x04]\x85\xa4p"

You may also compute hashes incrementally

    >>> from eth_hash.auto import keccak
    >>> preimage = keccak.new(b'part-a')
    >>> preimage.update(b'part-b')
    >>> preimage.digest()
    b'6\x91l\xdd50\xd6[\x7f\xf9B\xff\xc9SW\x98\xc3\xaal\xd9\xde\xdd6I\xb7\x91\x9e\xf4`pl\x08'

The preimage object returned may be copied as well.

    >>> from eth_hash.auto import keccak
    >>> preimage = keccak.new(b'part-a')
    >>> preimage_copy = preimage.copy()
    >>> preimage.update(b'part-b')
    >>> preimage.digest()
    b'6\x91l\xdd50\xd6[\x7f\xf9B\xff\xc9SW\x98\xc3\xaal\xd9\xde\xdd6I\xb7\x91\x9e\xf4`pl\x08'
    >>> preimage_copy.update(b'part-c')
    >>> preimage_copy.digest()
    b'\xffcy45\xea\xdd\xdf\x8e(\x1c\xfcF\xf3\xd4\xa1S\x0f\xdf\xd8\x01!\xb2(\xe1\xc7\xc6\xa3\x08\xc3\n\x0b'

  Select one of many installed backends

If you have several backends installed, you may want to explicitly specify which one to load. You can specify in an environment variable, or at runtime.

  Specify backend by environment variable

    $ ETH_HASH_BACKEND="pysha3" python
    >>> from eth_hash.auto import keccak
    # This runs with the pysha3 backend
    >>> keccak(b'')
    b"\xc5\xd2F\x01\x86\xf7#<\x92~}\xb2\xdc\xc7\x03\xc0\xe5\x00\xb6S\xca\x82';{\xfa\xd8\x04]\x85\xa4p"

  Specify backend at runtime

    >>> from eth_hash.backends import pysha3
    >>> from eth_hash import Keccak256
    >>> keccak = Keccak256(pysha3)
    >>> keccak(b'')
    b"\xc5\xd2F\x01\x86\xf7#<\x92~}\xb2\xdc\xc7\x03\xc0\xe5\x00\xb6S\xca\x82';{\xfa\xd8\x04]\x85\xa4p"

  eth_hash.backends package

  Submodules

  eth_hash.backends.auto module

  eth_hash.backends.pycryptodome module

  eth_hash.backends.pysha3 module

  Module contents

  eth_hash package

  eth_hash.auto module

  eth_hash.main module

  Release Notes

  eth-hash v0.8.0 (2026-03-25)

No significant changes.

  eth-hash v0.8.0-beta.1 (2025-12-17)

  Breaking Changes

•   Drop support for Python 3.8 and 3.9 (#66 <https://github.com/ethereum/eth-hash/issues/66>)

  Features

•   Add support for Python 3.14 (#66 <https://github.com/ethereum/eth-hash/issues/66>)

  eth-hash v0.7.1 (2025-01-13)

  Internal Changes - for eth-hash Contributors

•   Merge template, updating CI runs and what is included in package files (#59 <https://github.com/ethereum/eth-hash/issues/59>)

•   Run mypy linting locally via a pre-commit hook (#60 <https://github.com/ethereum/eth-hash/issues/60>)

•   Merge template updates, notably adding support for py313 and moving docs from the README to ReadTheDocs (#61 <https://github.com/ethereum/eth-hash/issues/61>)

  eth-hash v0.7.0 (2024-03-01)

  Internal Changes - for eth-hash Contributors

•   Merge template updates, notably adding py312 support and testing docs build for all formats (#57 <https://github.com/ethereum/eth-hash/issues/57>)

  eth-hash v0.6.0 (2024-01-10)

  Breaking Changes

•   Drop python 3.7 support (#53 <https://github.com/ethereum/eth-hash/issues/53>)

  Internal Changes - for eth-hash Contributors

•   Merge project template updates, notably use pre-commit for linting and change the name of master branch to main (#53 <https://github.com/ethereum/eth-hash/issues/53>)

•   Correct booleans in pyproject.toml and add test for presence of eth_hash.__version__ attribute (#55 <https://github.com/ethereum/eth-hash/issues/55>)

  eth-hash v0.5.2 (2023-06-07)

  Internal Changes - for eth-hash Contributors

•   remove unused docs deps, bump version of remaining (#48 <https://github.com/ethereum/eth-hash/issues/48>)

•   merge updates from the python project template (#51 <https://github.com/ethereum/eth-hash/issues/51>)

  eth-hash v0.5.1 (2022-11-09)

  Features

•   Add support for Python 3.11 (#45 <https://github.com/ethereum/eth-hash/issues/45>)

  eth-hash v0.5.0 (2022-07-20)

  Performance improvements

•   Prefer pysha3 backend by default (#42 <https://github.com/ethereum/eth-hash/issues/42>)

  eth-hash v0.4.0 (2022-07-06)

  Features

•   Add support for Python 3.8, 3.9, 3.10 (#40 <https://github.com/ethereum/eth-hash/issues/40>)

  Deprecations and Removals

•   Drop support for Python 3.5 and 3.6 (#39 <https://github.com/ethereum/eth-hash/issues/39>)

  Miscellaneous changes

•   #40 <https://github.com/ethereum/eth-hash/issues/40>, #41 <https://github.com/ethereum/eth-hash/issues/41>

  eth-hash v0.3.3 (2022-06-30)

  Performance improvements

•   Keccak backend was initialized every time it was called. Now it's initialized only the first time it's called. (#36 <https://github.com/ethereum/eth-hash/issues/36>)

  Internal Changes - for eth-hash Contributors

•   Prune venv files from the release via MANIFEST.in (#38 <https://github.com/ethereum/eth-hash/issues/38>)

  eth-hash v0.3.2 (2021-09-03)

  Miscellaneous changes

•   Drop eth-utils requirement, to fix dependency cycle (#33 <https://github.com/ethereum/eth-hash/issues/33>)

  eth-hash v0.3.1 (2021-01-21)

  Bugfixes

•   Bugfix to export type annotations (#28 <https://github.com/ethereum/eth-hash/issues/28>)

  eth-hash v0.3.0 (2021-01-20)

  Features

•   Export type annotations, for use in importing projects (#29 <https://github.com/ethereum/eth-hash/issues/29>)

  Internal Changes - for eth-hash Contributors

•   Import 3 years worth of template updates (#29 <https://github.com/ethereum/eth-hash/issues/29>)

  v0.2.0

Released September 5, 2018

•   set pycryptodome version to >=3.6.6,<4 to fix a recently discovered vulnerability

  v0.1.4

Released May 28, 2018

•   Ensure the auto backend is pickleable (#19)

  v0.1.3

Released May 14, 2018

•   The pycryptodome backend now allows update(), then digest(), then update().

  v0.1.2

Released Apr 2, 2018

•   You can now import eth-hash without a backend, it won't fail until trying to generate a hash

  v0.1.1

Released Mar 15, 2018

•   upgrade pycryptodome to v3.5.1+

•   performance improvements with preimage

•   Better docs and tests

  v0.1.0

Released Feb 28, 2018

•   Add support for bytearray <https://docs.python.org/3.10/library/stdtypes.html#bytearray> input to keccak

•   Add support for incrementally building hash results

  v0.1.0-alpha.3

Released Feb 7, 2018

•   Add pycryptodome backend support

•   Add pysha3 backend support

•   Can specify backend in environment variable ETH_HASH_BACKEND

•   New Quickstart <#quickstart> docs

  v0.1.0-alpha.2

Released Feb 6, 2018

•   Bugfix pypy3 reference in pypi

  v0.1.0-alpha.1

•   Launched repository, claimed names for pip, RTD, github, etc

  Contributing

Thank you for your interest in contributing! We welcome all contributions no matter their size. Please read along to learn how to get started. If you get stuck, feel free to ask for help in Ethereum Python Discord server <https://discord.gg/GHryRvPB84>.

  Setting the stage

To get started, fork the repository to your own github account, then clone it to your development machine:

    git clone git@github.com:your-github-username/eth-hash.git

Next, install the development dependencies. We recommend using a virtual environment, such as virtualenv <https://virtualenv.pypa.io/en/stable/>.

    cd eth-hash
    virtualenv -p python venv
    . venv/bin/activate
    python -m pip install -e ".[dev]"
    pre-commit install

  Running the tests

A great way to explore the code base is to run the tests.

We can run all tests with:

    pytest tests

  Code Style

We use pre-commit <https://pre-commit.com/> to enforce a consistent code style across the library. This tool runs automatically with every commit, but you can also run it manually with:

    make lint

If you need to make a commit that skips the pre-commit checks, you can do so with git commit --no-verify.

This library uses type hints, which are enforced by the mypy tool (part of the pre-commit checks). All new code is required to land with type hints, with the exception of code within the tests directory.

  Documentation

Good documentation will lead to quicker adoption and happier users. Please check out our guide on how to create documentation for the Python Ethereum ecosystem <https://github.com/ethereum/snake-charmers-tactical-manual/blob/main/documentation.md>.

  Pull Requests

It's a good idea to make pull requests early on. A pull request represents the start of a discussion, and doesn't necessarily need to be the final, finished submission.

GitHub's documentation for working on pull requests is available here <https://docs.github.com/pull-requests/collaborating-with-pull-requests/proposing-changes-to-your-work-with-pull-requests/about-pull-requests>.

Once you've made a pull request, take a look at the Circle CI build status in the GitHub interface and make sure all tests are passing. In general pull requests that do not pass the CI build yet won't get reviewed unless explicitly requested.

If the pull request introduces changes that should be reflected in the release notes, please add a newsfragment file as explained here <https://github.com/ethereum/eth-hash/blob/main/newsfragments/README.md>.

If possible, the change to the release notes file should be included in the commit that introduces the feature or bugfix.

  Releasing

Releases are typically done from the main branch, except when releasing a beta (in which case the beta is released from main, and the previous stable branch is released from said branch).

  Final review before each release

Before releasing a new version, build and test the package that will be released:

    git checkout main && git pull
    make package-test

This will build the package and install it in a temporary virtual environment. Follow the instructions to activate the venv and test whatever you think is important.

Review the documentation that will get published:

    make docs

Validate and preview the release notes:

    make validate-newsfragments

  Build the release notes

Before bumping the version number, build the release notes. You must include the part of the version to bump (see below), which changes how the version number will show in the release notes.

    make notes bump=$$VERSION_PART_TO_BUMP$$

If there are any errors, be sure to re-run make notes until it works.

  Push the release to github & pypi

After confirming that the release package looks okay, release a new version:

    make release bump=$$VERSION_PART_TO_BUMP$$

This command will:

•   Bump the version number as specified in .pyproject.toml and setup.py.

•   Create a git commit and tag for the new version.

•   Build the package.

•   Push the commit and tag to github.

•   Push the new package files to pypi.

  Which version part to bump

$$VERSION_PART_TO_BUMP$$ must be one of: major, minor, patch, stage, or devnum.

The version format for this repo is {major}.{minor}.{patch} for stable, and {major}.{minor}.{patch}-{stage}.{devnum} for unstable (stage can be alpha or beta).

If you are in a beta version, make release bump=stage will switch to a stable.

To issue an unstable version when the current version is stable, specify the new version explicitly, like make release bump="--new-version 4.0.0-alpha.1"

You can see what the result of bumping any particular version part would be with bump-my-version show-bump

  Code of Conduct

  Our Pledge

In the interest of fostering an open and welcoming environment, we as contributors and maintainers pledge to make participation in our project and our community a harassment-free experience for everyone, regardless of age, body size, disability, ethnicity, gender identity and expression, level of experience, education, socio-economic status, nationality, personal appearance, race, religion, or sexual identity and orientation.

  Our Standards

Examples of behavior that contributes to creating a positive environment include:

•   Using welcoming and inclusive language

•   Being respectful of differing viewpoints and experiences

•   Gracefully accepting constructive criticism

•   Focusing on what is best for the community

•   Showing empathy towards other community members

    Examples of unacceptable behavior by participants include:

•   The use of sexualized language or imagery and unwelcome sexual attention or advances

•   Trolling, insulting/derogatory comments, and personal or political attacks

•   Public or private harassment

•   Publishing others' private information, such as a physical or electronic address, without explicit permission

•   Other conduct which could reasonably be considered inappropriate in a professional setting

  Our Responsibilities

Project maintainers are responsible for clarifying the standards of acceptable behavior and are expected to take appropriate and fair corrective action in response to any instances of unacceptable behavior.

Project maintainers have the right and responsibility to remove, edit, or reject comments, commits, code, wiki edits, issues, and other contributions that are not aligned to this Code of Conduct, or to ban temporarily or permanently any contributor for other behaviors that they deem inappropriate, threatening, offensive, or harmful.

  Scope

This Code of Conduct applies both within project spaces and in public spaces when an individual is representing the project or its community. Examples of representing a project or community include using an official project e-mail address, posting via an official social media account, or acting as an appointed representative at an online or offline event. Representation of a project may be further defined and clarified by project maintainers.

  Enforcement

Instances of abusive, harassing, or otherwise unacceptable behavior may be reported by contacting the project team at <snakecharmers@ethereum.org>. All complaints will be reviewed and investigated and will result in a response that is deemed necessary and appropriate to the circumstances. The project team is obligated to maintain confidentiality with regard to the reporter of an incident. Further details of specific enforcement policies may be posted separately.

Project maintainers who do not follow or enforce the Code of Conduct in good faith may face temporary or permanent repercussions as determined by other members of the project's leadership.

  Attribution

This Code of Conduct is adapted from the Contributor Covenant <https://www.contributor-covenant.org>, version 1.4, available at <https://www.contributor-covenant.org/version/1/4/code-of-conduct.html>

INDICES AND TABLES

•   Index <>

•   Module Index <>

Author
The Ethereum Foundation

Copyright
2018-2025, The Ethereum Foundation