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Editing: random-numbers.rst
Random number generation ======================== When generating random data for use in cryptographic operations, such as an initialization vector for encryption in :class:`~cryptography.hazmat.primitives.ciphers.modes.CBC` mode, you do not want to use the standard :mod:`random` module APIs. This is because they do not provide a cryptographically secure random number generator, which can result in major security issues depending on the algorithms in use. Therefore, it is our recommendation to `always use your operating system's provided random number generator`_, which is available as :func:`os.urandom`. For example, if you need 16 bytes of random data for an initialization vector, you can obtain them with: .. doctest:: >>> import os >>> iv = os.urandom(16) If you need your random number as an big integer, you can use ``int.from_bytes`` to convert the result of ``os.urandom``: .. code-block:: pycon >>> serial = int.from_bytes(os.urandom(16), byteorder="big") In addition, the `Python standard library`_ includes the ``secrets`` module, which can be used for generating cryptographically secure random numbers, with specific helpers for text-based formats. .. _`always use your operating system's provided random number generator`: https://sockpuppet.org/blog/2014/02/25/safely-generate-random-numbers/ .. _`Python standard library`: https://docs.python.org/3/library/secrets.html
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