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- Frequently asked questions
- ==========================
- ``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
- and trying ``pip install cryptography`` again, please see the :doc:`/installation`
- documentation.
- 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 :ref:`recipes <cryptography-layout>` layer has similar goals
- to NaCl.
- If you prefer NaCl's design, we highly recommend `PyNaCl`_, which is also
- maintained by the PyCA team.
- Why use ``cryptography``?
- -------------------------
- If you've done cryptographic work in Python before you have likely encountered
- other libraries in Python such as *M2Crypto*, *PyCrypto*, or *PyOpenSSL*. In
- building ``cryptography`` we wanted to address a few issues we observed in the
- legacy libraries:
- * Extremely error prone APIs and insecure defaults.
- * Use of poor implementations of algorithms (i.e. ones with known side-channel
- attacks).
- * Lack of maintenance.
- * Lack of high level APIs.
- * Lack of PyPy and Python 3 support.
- * Absence of algorithms such as
- :class:`AES-GCM <cryptography.hazmat.primitives.ciphers.modes.GCM>` and
- :class:`~cryptography.hazmat.primitives.kdf.hkdf.HKDF`.
- Compiling ``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
- try install ``cryptography`` again.
- 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
- Homebrew.
- ``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.
- error: ``-Werror=sign-conversion``: No option ``-Wsign-conversion`` during installation
- ---------------------------------------------------------------------------------------
- The compiler you are using is too old and not supported by ``cryptography``.
- 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
- newer ``gcc`` and then install ``cryptography`` using
- ``CC=/path/to/newer/gcc pip install cryptography``.
- Installing ``cryptography`` fails with ``Invalid environment marker: python_version < '3'``
- -------------------------------------------------------------------------------------------
- Your ``pip`` and/or ``setuptools`` are outdated. Please upgrade to the latest
- versions with ``pip install -U pip setuptools`` (or on Windows
- ``python -m pip install -U pip setuptools``).
- Importing cryptography causes a ``RuntimeError`` about OpenSSL 1.0.1
- --------------------------------------------------------------------
- The OpenSSL project has dropped support for the 1.0.1 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 (1.0.2 or later). This may require you to upgrade to a newer
- operating system.
- For the 2.9 release, you can set the ``CRYPTOGRAPHY_ALLOW_OPENSSL_101``
- environment variable. Please note that this is *temporary* and will be removed
- in ``cryptography`` 3.0.
- Installing cryptography with OpenSSL 0.9.8 or 1.0.0 fails
- ---------------------------------------------------------
- The OpenSSL project has dropped support for the 0.9.8 and 1.0.0 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 ``abi3`` wheels.
- ``ImportError``: ``idna`` is not installed
- ------------------------------------------
- ``cryptography`` deprecated passing :term:`U-label` strings to various X.509
- constructors in version 2.1 and in version 2.5 moved the ``idna`` dependency
- to a ``setuptools`` extra. If you see this exception you should upgrade your
- software so that it no longer depends on this deprecated feature. If that is
- not yet possible you can also install ``cryptography`` with
- ``pip install cryptography[idna]`` to automatically install the missing
- dependency. This workaround will be available until the feature is fully
- removed.
- 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 ``[FILE TYPE]`` is ``CERTIFICATE``, ``PUBLIC KEY``, ``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-----
- .. _`NaCl`: https://nacl.cr.yp.to/
- .. _`PyNaCl`: https://pynacl.readthedocs.io
- .. _`WSGIApplicationGroup`: https://modwsgi.readthedocs.io/en/develop/configuration-directives/WSGIApplicationGroup.html
- .. _`issue`: https://github.com/pyca/cryptography/issues
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