PyHSM - Python YubiHSM Project


PyHSM is a Python package to talk to a YubiHSM. The YubiHSM is Yubico’s take on the Hardware Security Module (HSM), designed for protecting secrets on authentication servers, including cryptographic keys and passwords, at unmatched simplicity and low cost.


The project is licensed under the BSD license, see the file COPYING for exact wording.


PyHSM aims to be a reference implementation implementing all the functions available in the YubiHSM.

PyHSM also includes the regression test suite for the YubiHSM. Instructions on running this test suite can be found in test/README.adoc.

In general, see the files in examples/ to get an idea of how to use this code.

In addition to the YubiHSM communication library, PyHSM also contains some applications utilizing the YubiHSM:

  • yhsm-val: a simple validation server supporting validation of YubiKey OTPs, OATH codes and password hashes.

  • yubikey-ksm: ykval YubiKey OTP decryption backend using the YubiHSM.

Some smaller scripts are also available:

  • yhsm-linux-add-entropy: Feed Linux kernel with random entropy from the TRNG on the YubiHSM.

  • yhsm-keystore-unlock: Unlock the key storage in the YubiHSM with your HSM password. Use with incorrect password to lock it again.

  • yhsm-daemon: Talk to the YubiHSM directly over TCP.

And some more in examples/:

  • Print basic system information about the connected YubiHSM.

  • Get a YubiHSM in debug mode to enter configuration mode again, without having to press the little button while inserting it into the USB port.

  • Example of how to turn passwords (or hashes of passwords if you like PBKDF2) into AEADs that can be used to verify the password later on.


PyHSM is known to work with Python 2.6 and 2.7, and is primarily tested using Debian/Ubuntu, but is of course meant to work on as many platforms as possible.

If you want to use any of the daemons (yhsm-validation-server, yhsm-yubikey-ksm) you will want to use Python 2.7 or later. lacks critical timeout handling in Python 2.6.

The pyserial package is needed.

Debian: apt-get install python-serial

You will also need pycrypto.

Debian: apt-get install python-crypto

Please note that the pycrypto version has to be 2.1 or higher — it is known that RHEL6 has a lower version.

For database support SQLAlchemy is needed.

Debian: apt-get install python-sqlalchemy

PyHSM easily installed via pip, which will also take care of the dependencies automatically, though some of these require other build dependencies to correctly install (note the added optional dependencies needed for yubikey-ksm, yhsm-val and tools):

pip install pyhsm[db,daemon]

or, on Debian based systems (dependencies will also be handled automatically):

sudo apt-get install python-pyhsm

additional Debian packages available are:

yhsm-tools yhsm-yubikey-ksm yhsm-validation-server yhsm-daemon

Working with the source code repository

To work with the source code repository, if you wish to build your own release or contribute pull requests, follow these steps to set up your environment. If you just wish to install the application use the source release packages. This project is developed on a Debian based system, other OSes may not be supported for development.

Check out the code

Run these commands to check out the source code:

git clone
cd python-pyhsm