Frequently asked questions

How does cryptography compare to NaCl (Networking and Cryptography Library)?

While cryptography and NaCl both share the goal of making cryptography easier, and safer, to use for developers, cryptography is designed to be a general purpose library, interoperable with existing systems, while NaCl features a collection of hand selected algorithms.

cryptography‘s recipes layer has similar goals to NaCl.

If you prefer NaCl’s design, we highly recommend PyNaCl.

Compiling cryptography on OS X produces a fatal error: 'openssl/aes.h' file not found error

This happens because OS X 10.11 no longer includes a copy of OpenSSL. cryptography now provides wheels which include a statically linked copy of OpenSSL. You’re seeing this error because your copy of pip is too old to find our wheel files. Upgrade your copy of pip with pip install -U pip and then try install cryptography again.

Starting cryptography using mod_wsgi produces an InternalError during a call in _register_osrandom_engine

This happens because mod_wsgi uses sub-interpreters, which can cause a problem during initialization of the OpenSSL backend. To resolve this set the WSGIApplicationGroup to %{GLOBAL} in the mod_wsgi configuration.

cryptography raised an InternalError and I’m not sure what to do?

Frequently InternalError is raised when there are errors on the OpenSSL error stack that were placed there by other libraries that are also using OpenSSL. Try removing the other libraries and see if the problem persists. If you have no other libraries using OpenSSL in your process, or they do not appear to be at fault, it’s possible that this is a bug in cryptography. Please file an issue with instructions on how to reproduce it.

Importing cryptography causes a RuntimeError about OpenSSL 1.0.0

The OpenSSL project has dropped support for the 1.0.0 release series. Since it is no longer receiving security patches from upstream, cryptography is also dropping support for it. To fix this issue you should upgrade to a newer version of OpenSSL (1.0.1 or later). This may require you to upgrade to a newer operating system.

For the 1.7 release, you can set the CRYPTOGRAPHY_ALLOW_OPENSSL_100 environment variable. Please note that this is temporary and will be removed in cryptography 1.8.

Installing cryptography with OpenSSL 0.9.8 fails

The OpenSSL project has dropped support for the 0.9.8 release series. Since it is no longer receiving security patches from upstream, cryptography is also dropping support for it. To fix this issue you should upgrade to a newer version of OpenSSL (1.0.1 or later). This may require you to upgrade to a newer operating system.