Python library and tests for the YubiHSM 2.

The current version (3.0) supports Python 3.8 and later.

Communicates with the YubiHSM 2 connector daemon, which must already be running. It can also communicate directly with the YubiHSM 2 via USB (requires libusb).


Copyright 2023 Yubico AB

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
See the License for the specific language governing permissions and
limitations under the License.


From PyPI:

pip install yubihsm[http,usb]

From a source .tar.gz:

pip install yubihsm-<version>.tar.gz[http,usb]

Omitting a tag from the brackets will install the library without support for that backend, and will avoid installing unneeded dependencies.

Quick reference commands:

from yubihsm import YubiHsm
from yubihsm.defs import CAPABILITY, ALGORITHM
from yubihsm.objects import AsymmetricKey

# Connect to the YubiHSM via the connector using the default password:
hsm = YubiHsm.connect('http://localhost:12345')
session = hsm.create_session_derived(1, 'password')

# Generate a private key on the YubiHSM for creating signatures:
key = AsymmetricKey.generate(  # Generate a new key object in the YubiHSM.
    session,                   # Secure YubiHsm session to use.
    0,                         # Object ID, 0 to get one assigned.
    'My key',                  # Label for the object.
    1,                         # Domain(s) for the object.
    CAPABILITY.SIGN_ECDSA,     # Capabilities for the object, can have multiple.
    ALGORITHM.EC_P256          # Algorithm for the key.

# pub_key is a ec.PublicKey, see
pub_key = key.get_public_key()

# Write the public key to a file:
with open('public_key.pem', 'w') as f:

# Sign some data:
signature = key.sign_ecdsa(b'Hello world!')  # Create a signature.

# Clean up:


For development of the library, poetry is used. To set up the dev environment, run this command in the root directory of the repository:

poetry install -E http -E usb

Pre-commit checks

This project uses to run several checks on the code prior to committing. To enable the hooks, run this command in the root directory of the repository:

pre-commit install

Once the hooks are installed, they will run automatically on any changed files when committing. To run the hooks against all files in the repository, run:

pre-commit run --all-files

Running tests

Running the tests require a YubiHSM2 to run against, with the default authentication key enabled (as is the case after performing a factory reset).

The YubiHSM under test will be factory reset by the tests!
poetry run pytest

See pytest documentation for instructions on running a specific test.

By default the tests will connect to a yubihsm-connector running with the default settings on http://localhost:12345. To change this, use the --backend argument, eg:

poetry run pytest --backend "yhusb://"

Access to the device requires proper permissions, so either use sudo or setup a udev rule. Sample udev configuration can be found here.

Generating HTML documentation

To build the HTML documentation, run:

poetry run make -C docs/ html

The resulting output will be in docs/_build/html/.

Source releases for distribution

Build a source release:

poetry build

The resulting .tar.gz and .whl will be created in dist/.