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A library that provides signing middlewares for any ASGI application.

Project description

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ASGI Signing Middleware

The goal of this project is to provide a simple and straightforward way to securely sign data by providing ready-to-use middlewares, using blake2signer as signing backend.

Why would I need to use it?

If you need to store some data (state, generally), and want to avoid using a trusted DB for performance reasons, it is usually advisable to sign said data. This package will help you achieve that with ease, ready-to-use middlewares, without you needing to think on the details: just provide a signing secret and let this package handle the rest.

Why would I want to use it?

Because it is a relatively small (around 100 logical lines of code), simple (usage is very straight-forward) yet very customizable and fast middleware data signer. My idea is to keep it as uncomplicated as possible without much room to become a footgun. All defaults are very sane (secure) and everything just works out of the box.


  • Be safe and secure.
  • Be simple and straightforward.
  • Follow semver.
  • Be always typed.
  • 100% coverage.

Secondary goals

  • If possible, maintain active Python versions (3.8+).


This package is hosted on PyPi so just:

  • python3 -m pip install asgi-signing-middleware
  • poetry add asgi-signing-middleware
  • pipenv install asgi-signing-middleware

You can check the releases' page for package hashes and signatures.


Versions currently tested (check the pipelines):

  • CPython 3.8
  • CPython 3.9
  • CPython 3.10
  • CPython 3.11
  • PyPy 3.8
  • Stackless 3.8

Tl; Dr Example

"""Tl;dr example."""

import typing

from fastapi import FastAPI
from fastapi import Request

from asgi_signing_middleware import SerializedSignedCookieMiddleware

app = FastAPI()
    SerializedSignedCookieMiddleware,  # Any of the middlewares
    # Follows the middleware parameters
    secret=b'a very, very secret thing',  # This should probably come from some configs
    state_attribute_name='messages',  # Use in a request handler as `request.state.messages`
    cookie_ttl=60 * 5,  # 5 minutes, in seconds
    # You can also set extra signer kwargs and cookie properties, check the middleware
    # init for more info.

def cookie_endpoint(request: Request) -> None:
    # This will only have data that was correctly signed, or None
    cookie_data: typing.Optional[typing.Dict[str, str]] = request.state.messages

    # ...

    # This will be signed and written into the cookie
    request.state.messages = {'A Title': 'The message', 'Another title': 'With another msg'}

Tip: all modules, classes, methods and functions are documented so don't doubt asking for help().


Check out this project docs online or locally with inv docs. Alternatively, build them locally using inv docs --build.


I'm not a cryptoexpert, so this project needs a security review. If you are one and can do it, please contact me.


ASGI Signing Middleware is made by HacKan under MPL v2.0. You are free to use, share, modify and share modifications under the terms of that license. Derived works may link back to the canonical repository:

Copyright (C) 2022 HacKan (
This Source Code Form is subject to the terms of the Mozilla Public
License, v. 2.0. If a copy of the MPL was not distributed with this
file, You can obtain one at

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