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data::entropy
Data::Entropy(3pm) User Contributed Perl Documentation Data::Entropy(3pm)
NAME
Data::Entropy - entropy (randomness) management
SYNOPSIS
use Data::Entropy qw(entropy_source);
$i = entropy_source->get_int(12345);
use Data::Entropy qw(with_entropy_source);
with_entropy_source $source, sub {
@a = shuffle(@a);
};
DESCRIPTION
This module maintains a concept of a current selection of entropy source. Algorithms that require entropy, such as those in
Data::Entropy::Algorithms, can use the source nominated by this module, avoiding the need for entropy source objects to be explicitly
passed around. This is convenient because usually one entropy source will be used for an entire program run and so an explicit entropy
source parameter would rarely vary. There is also a default entropy source, avoiding the need to explicitly configure a source at all.
If nothing is done to set a source then it defaults to the use of Rijndael (AES) in counter mode (see
Data::Entropy::RawSource::CryptCounter and Crypt::Rijndael), keyed using Perl's built-in "rand" function. This gives a data stream that
looks like concentrated entropy, but really only has at most the entropy of the "rand" seed. Within a single run it is cryptographically
difficult to detect the correlation between parts of the pseudo-entropy stream. If more true entropy is required then it is necessary to
configure a different entropy source.
FUNCTIONS
entropy_source
Returns the current entropy source, a "Data::Entropy::Source" object. This will be the source passed to the innermost call to
"with_entropy_source", if any, or otherwise the default entropy source.
with_entropy_source SOURCE, CLOSURE
The SOURCE is selected, so that it will be returned by "entropy_source", and CLOSURE is called (with no arguments). The SOURCE is
selected only during the dynamic scope of the call; after CLOSURE finishes, by whatever means, the previously selected entropy source
is restored.
SOURCE is normally a "Data::Entropy::Source" object. Alternatively, it may be "undef" to cause use of the default entropy source. It
may also be a reference to a function of no arguments, which will be called to generate the actual source only if required. This
avoids unnecessarily initialising the source object if it is uncertain whether any entropy will be required. The source-generating
closure may return a normal source or "undef", but not another function reference.
SEE ALSO
Data::Entropy::Algorithms, Data::Entropy::Source
AUTHOR
Andrew Main (Zefram) <zefram@fysh.org>
COPYRIGHT
Copyright (C) 2006, 2007, 2009, 2011 Andrew Main (Zefram) <zefram@fysh.org>
LICENSE
This module is free software; you can redistribute it and/or modify it under the same terms as Perl itself.
perl v5.12.3 2011-05-09 Data::Entropy(3pm)
