Data::Entropy::RawSource::CryptCounter(3pm)

1Data::Entropy::RawSourcUes:e:rCrCyopnttCroiubnutteerdD(a3Pt)ear:l:EDnotcruompeyn:t:aRtaiwoSnource::CryptCounter(3)
2
3
4

NAME

6       Data::Entropy::RawSource::CryptCounter - counter mode of block cipher
7       as I/O handle
8

SYNOPSIS

10               use Data::Entropy::RawSource::CryptCounter;
11
12               my $rawsrc = Data::Entropy::RawSource::CryptCounter
13                               ->new(Crypt::Rijndael->new($key));
14
15               $c = $rawsrc->getc;
16               # and the rest of the I/O handle interface
17

DESCRIPTION

19       This class provides an I/O handle connected to a virtual file which
20       contains the output of a block cipher in counter mode.  This makes a
21       good source of pseudorandom bits.  The handle implements a substantial
22       subset of the interfaces described in IO::Handle and IO::Seekable.
23
24       For use as a general entropy source, it is recommended to wrap an
25       object of this class using "Data::Entropy::Source", which provides
26       methods to extract entropy in more convenient forms than mere octets.
27
28       The amount of entropy the virtual file actually contains is only the
29       amount that is in the key, which is at most the length of the key.  It
30       superficially appears to be much more than this, if (and to the extent
31       that) the block cipher is secure.  This technique is not suitable for
32       all problems, and requires a careful choice of block cipher and keying
33       method.  Applications requiring true entropy should generate it (see
34       Data::Entropy::RawSource::Local) or download it (see
35       Data::Entropy::RawSource::RandomnumbersInfo and
36       Data::Entropy::RawSource::RandomOrg).
37

CONSTRUCTOR

39       Data::Entropy::RawSource::CryptCounter->new(KEYED_CIPHER)
40           KEYED_CIPHER must be a cipher object supporting the standard
41           "blocksize" and "encrypt" methods.  For example, an instance of
42           "Crypt::Rijndael" (with the default "MODE_ECB") would be
43           appropriate.  A handle object is created and returned which refers
44           to a virtual file containing the output of the cipher's counter
45           mode.
46

METHODS

48       A subset of the interfaces described in IO::Handle and IO::Seekable are
49       provided:
50
51       $rawsrc->read(BUFFER, LENGTH[, OFFSET])
52       $rawsrc->getc
53       $rawsrc->ungetc(ORD)
54       $rawsrc->eof
55           Buffered reading from the source, as in IO::Handle.
56
57       $rawsrc->sysread(BUFFER, LENGTH[, OFFSET])
58           Unbuffered reading from the source, as in IO::Handle.
59
60       $rawsrc->close
61           Does nothing.
62
63       $rawsrc->opened
64           Retruns true to indicate that the source is available for I/O.
65
66       $rawsrc->clearerr
67       $rawsrc->error
68           Error handling, as in IO::Handle.
69
70       $rawsrc->getpos
71       $rawsrc->setpos(POS)
72       $rawsrc->tell
73       $rawsrc->seek(POS, WHENCE)
74           Move around within the buffered source, as in IO::Seekable.
75
76       $rawsrc->sysseek(POS, WHENCE)
77           Move around within the unbuffered source, as in IO::Seekable.
78
79       The buffered ("read" et al) and unbuffered ("sysread" et al) sets of
80       methods are interchangeable, because no such distinction is made by
81       this class.
82
83       "tell", "seek", and "sysseek" only work within the first 4 GiB of the
84       virtual file.  The file is actually much larger than that: for Rijndael
85       (AES), or any other cipher with a 128-bit block, the file is 2^52 YiB
86       (2^132 B).  "getpos" and "setpos" work throughout the file.
87
88       Methods to write to the file are unimplemented because the virtual file
89       is fundamentally read-only.
90

AUTHOR

97       Andrew Main (Zefram) <zefram@fysh.org>
98

COPYRIGHT

100       Copyright (C) 2006, 2007, 2009, 2011 Andrew Main (Zefram)
101       <zefram@fysh.org>
102

LICENSE

104       This module is free software; you can redistribute it and/or modify it
105       under the same terms as Perl itself.
106
107
108
109perl v5.30.0                      2019D-a0t7a-:2:6Entropy::RawSource::CryptCounter(3)