Frequently asked questions¶
I cannot suppress the deprecation warning that
cryptography emits on import¶
If your pytest setup follows the best practices of failing on
emitted warnings (
filterwarnings = error), you may ignore it
by adding the following line at the end of the list:
ignore:Python 2 is no longer supported by the Python core team. Support for it is now deprecated in cryptography, and will be removed in a future release.:UserWarning:cryptography
is not possible here because specifying it triggers
import cryptography internally that emits the warning before
the ignore rule even kicks in.
cryptography failed to install!¶
If you are having issues installing
cryptography the first troubleshooting
step is to upgrade
pip and then try to install again. For most users this will
take the form of
pip install -U pip, but on Windows you should do
python -m pip install -U pip. If you are still seeing errors after upgrading
pip install cryptography again, please see the Installation
cryptography compare to NaCl (Networking and Cryptography Library)?¶
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
If you prefer NaCl’s design, we highly recommend PyNaCl, which is also maintained by the PyCA team.
If you’ve done cryptographic work in Python before you have likely encountered
other libraries in Python such as M2Crypto, PyCrypto, or PyOpenSSL. In
cryptography we wanted to address a few issues we observed in the
cryptography on macOS produces a
fatal error: 'openssl/aes.h' file not found error¶
This happens because macOS 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
If you are using PyPy, we do not currently ship
cryptography wheels for
PyPy. You will need to install your own copy of OpenSSL – we recommend using
cryptography raised an
InternalError and I’m not sure what to do?¶
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
Please file an issue with instructions on how to reproduce it.
-Werror=sign-conversion: No option
-Wsign-conversion during installation¶
The compiler you are using is too old and not supported by
Please upgrade to a more recent version. If you are running OpenBSD 6.1 or
earlier the default compiler is extremely old. Use
pkg_add to install a
gcc and then install
CC=/path/to/newer/gcc pip install cryptography.
cryptography fails with
Invalid environment marker: python_version < '3'¶
setuptools are outdated. Please upgrade to the latest
pip install -U pip setuptools (or on Windows
python -m pip install -U pip setuptools).
Installing cryptography with OpenSSL 0.9.8, 1.0.0, 1.0.1 fails¶
The OpenSSL project has dropped support for the 0.9.8, 1.0.0, and 1.0.1 release
series. Since they are no longer receiving security patches from upstream,
cryptography is also dropping support for them. To fix this issue you
should upgrade to a newer version of OpenSSL (1.0.2 or later). This may require
you to upgrade to a newer operating system.
Why are there no wheels for Python 3.6+ on Linux or macOS?¶
Our Python3 wheels, for macOS and Linux, are
abi3 wheels. This means they
support multiple versions of Python. The Python 3.5
abi3 wheel can be used
with any version of Python greater than or equal to 3.5. Recent versions of
pip will automatically install
Why can’t I import my PEM file?¶
PEM is a format (defined by several RFCs, but originally RFC 1421) for encoding keys, certificates and others cryptographic data into a regular form. The data is encoded as base64 and wrapped with a header and footer.
If you are having trouble importing PEM files, make sure your file fits the following rules:
- has a one-line header like this:
-----BEGIN [FILE TYPE]-----(where
PRIVATE KEY, etc.)
- has a one-line footer like this:
-----END [FILE TYPE]-----
- all lines, except for the final one, must consist of exactly 64 characters.
For example, this is a PEM file for a RSA Public Key:
-----BEGIN PUBLIC KEY----- MIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEA7CsKFSzq20NLb2VQDXma 9DsDXtKADv0ziI5hT1KG6Bex5seE9pUoEcUxNv4uXo2jzAUgyRweRl/DLU8SoN8+ WWd6YWik4GZvNv7j0z28h9Q5jRySxy4dmElFtIRHGiKhqd1Z06z4AzrmKEzgxkOk LJjY9cvwD+iXjpK2oJwNNyavvjb5YZq6V60RhpyNtKpMh2+zRLgIk9sROEPQeYfK 22zj2CnGBMg5Gm2uPOsGDltl/I/Fdh1aO3X4i1GXwCuPf1kSAg6lPJD0batftkSG v0X0heUaV0j1HSNlBWamT4IR9+iJfKJHekOqvHQBcaCu7Ja4kXzx6GZ3M2j/Ja3A 2QIDAQAB -----END PUBLIC KEY-----