| 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 ``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) |
| |
| .. _`always use your operating system's provided random number generator`: http://sockpuppet.org/blog/2014/02/25/safely-generate-random-numbers/ |
