1Data::Entropy(3)      User Contributed Perl Documentation     Data::Entropy(3)
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NAME

6       Data::Entropy - entropy (randomness) management
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SYNOPSIS

9               use Data::Entropy qw(entropy_source);
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11               $i = entropy_source->get_int(12345);
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13               use Data::Entropy qw(with_entropy_source);
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15               with_entropy_source $source, sub {
16                       @a = shuffle(@a);
17               };
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DESCRIPTION

20       This module maintains a concept of a current selection of entropy
21       source.  Algorithms that require entropy, such as those in
22       Data::Entropy::Algorithms, can use the source nominated by this module,
23       avoiding the need for entropy source objects to be explicitly passed
24       around.  This is convenient because usually one entropy source will be
25       used for an entire program run and so an explicit entropy source
26       parameter would rarely vary.  There is also a default entropy source,
27       avoiding the need to explicitly configure a source at all.
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29       If nothing is done to set a source then it defaults to the use of
30       Rijndael (AES) in counter mode (see
31       Data::Entropy::RawSource::CryptCounter and Crypt::Rijndael), keyed
32       using Perl's built-in "rand" function.  This gives a data stream that
33       looks like concentrated entropy, but really only has at most the
34       entropy of the "rand" seed.  Within a single run it is
35       cryptographically difficult to detect the correlation between parts of
36       the pseudo-entropy stream.  If more true entropy is required then it is
37       necessary to configure a different entropy source.
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FUNCTIONS

40       entropy_source
41           Returns the current entropy source, a "Data::Entropy::Source"
42           object.  This will be the source passed to the innermost call to
43           "with_entropy_source", if any, or otherwise the default entropy
44           source.
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46       with_entropy_source SOURCE, CLOSURE
47           The SOURCE is selected, so that it will be returned by
48           "entropy_source", and CLOSURE is called (with no arguments).  The
49           SOURCE is selected only during the dynamic scope of the call; after
50           CLOSURE finishes, by whatever means, the previously selected
51           entropy source is restored.
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53           SOURCE is normally a "Data::Entropy::Source" object.
54           Alternatively, it may be "undef" to cause use of the default
55           entropy source.  It may also be a reference to a function of no
56           arguments, which will be called to generate the actual source only
57           if required.  This avoids unnecessarily initialising the source
58           object if it is uncertain whether any entropy will be required.
59           The source-generating closure may return a normal source or
60           "undef", but not another function reference.
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SEE ALSO

63       Data::Entropy::Algorithms, Data::Entropy::Source
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AUTHOR

66       Andrew Main (Zefram) <zefram@fysh.org>
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69       Copyright (C) 2006, 2007, 2009, 2011 Andrew Main (Zefram)
70       <zefram@fysh.org>
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LICENSE

73       This module is free software; you can redistribute it and/or modify it
74       under the same terms as Perl itself.
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78perl v5.34.0                      2022-01-21                  Data::Entropy(3)
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