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:py:mod:`rand` --- An interface to the OpenSSL pseudo random number generator
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=============================================================================
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.. py:module:: OpenSSL.rand
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:synopsis: An interface to the OpenSSL pseudo random number generator
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This module handles the OpenSSL pseudo random number generator (PRNG) and
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declares the following:
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.. py:function:: add(string, entropy)
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Mix bytes from *string* into the PRNG state. The *entropy* argument is
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(the lower bound of) an estimate of how much randomness is contained in
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*string*, measured in bytes. For more information, see e.g. :rfc:`1750`.
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.. py:function:: bytes(num_bytes)
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Get some random bytes from the PRNG as a string.
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This is a wrapper for the C function :py:func:`RAND_bytes`.
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.. py:function:: cleanup()
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Erase the memory used by the PRNG.
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This is a wrapper for the C function :py:func:`RAND_cleanup`.
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.. py:function:: egd(path[, bytes])
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Query the `Entropy Gathering Daemon <http://www.lothar.com/tech/crypto/>`_ on
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socket *path* for *bytes* bytes of random data and uses :py:func:`add` to
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seed the PRNG. The default value of *bytes* is 255.
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.. py:function:: load_file(path[, bytes])
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Read *bytes* bytes (or all of it, if *bytes* is negative) of data from the
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file *path* to seed the PRNG. The default value of *bytes* is -1.
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.. py:function:: screen()
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Add the current contents of the screen to the PRNG state.
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Availability: Windows.
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.. py:function:: seed(string)
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This is equivalent to calling :py:func:`add` with *entropy* as the length
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.. py:function:: status()
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Returns true if the PRNG has been seeded with enough data, and false otherwise.
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.. py:function:: write_file(path)
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Write a number of random bytes (currently 1024) to the file *path*. This
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file can then be used with :py:func:`load_file` to seed the PRNG again.
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.. py:exception:: Error
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If the current RAND method supports any errors, this is raised when needed.
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The default method does not raise this when the entropy pool is depleted.
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Whenever this exception is raised directly, it has a list of error messages
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from the OpenSSL error queue, where each item is a tuple *(lib, function,
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reason)*. Here *lib*, *function* and *reason* are all strings, describing
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where and what the problem is. See :manpage:`err(3)` for more information.
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doc/api/rand.rst
