1Crypt::Eksblowfish::UklUbsleorwfCiosnht(r3i)buted Perl DCorcyupmte:n:tEaktsibolnowfish::Uklblowfish(3)
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NAME

6       Crypt::Eksblowfish::Uklblowfish - Blowfish cipher with unrestricted key
7       length
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SYNOPSIS

10               use Crypt::Eksblowfish::Uklblowfish;
11
12               $block_size = Crypt::Eksblowfish::Uklblowfish->blocksize;
13               $key_size = Crypt::Eksblowfish::Uklblowfish->keysize;
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15               $cipher = Crypt::Eksblowfish::Uklblowfish->new($key);
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17               $block_size = $cipher->blocksize;
18               $ciphertext = $cipher->encrypt($plaintext);
19               $plaintext = $cipher->decrypt($ciphertext);
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21               $p_array = $cipher->p_array;
22               $s_boxes = $cipher->s_boxes;
23               if($cipher->is_weak) { ...
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DESCRIPTION

26       An object of this type encapsulates a keyed instance of the Blowfish
27       block cipher, ready to encrypt and decrypt.  However, if you're looking
28       for an implementation of Blowfish you most likely want
29       Crypt::Eksblowfish::Blowfish.  This class differs from the standard
30       Blowfish in that it accepts some keys that Blowfish officially does not
31       permit.
32
33       Blowfish is a symmetric cipher algorithm designed by Bruce Schneier in
34       1993.  It operates on 64-bit blocks, and takes a variable-length key.
35       Officially the key can vary from 32 bits (4 octets) to 448 bits (56
36       octets) in increments of 8 bits (1 octet).  In fact the algorithm can
37       easily operate on a key of any number of octets from 1 (8 bits) to 72
38       (576 bits).  Some implementations don't enforce the official key length
39       limits, and so for compatibility it is sometimes necessary to handle a
40       Blowfish key of a prohibited length.  That is what this class is for.
41       The "Ukl" in the name stands for "unrestricted key length".
42
43       Using a very short key is generally a bad idea because there aren't
44       very many keys of that length and so it's easy for an attacker to try
45       them all.  The official 32-bit minimum for Blowfish was already far too
46       short for serious security at the time that Blowfish was designed.  (A
47       machine to crack 56-bit DES keys by brute force in a few days each was
48       publicly built only five years later.)  Do not base your security on
49       the secrecy of a short key.
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51       Using overlong keys has more interesting effects, which depend on
52       internal features of Blowfish.  When the key exceeds 64 octets (512
53       bits), varying key bits past that length results in subkeys which have
54       predictable relationships.  There is also some possibility of
55       equivalent keys when the keys exceed 64 octets and differ only in the
56       first 8 octets (64 bits).  These phenomena have not been extensively
57       studied in the open literature, so it is difficult to judge the degree
58       of cryptographic weakness that results from them.  It is clear that
59       beyond some length Blowfish keys do not have as much strength as their
60       length would suggest, and it is possible that overlong keys have
61       specific weaknesses that render them weaker than shorter keys.  If
62       choosing a key for security, it is advised to stay within the official
63       length limit of 56 octets.
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65       In summary: using Blowfish keys of officially-unsupported lengths
66       causes security problems.  If you are using Blowfish for security, and
67       have the choice, use a key of an officially-supported length (and a
68       standard implementation such as Crypt::Eksblowfish::Blowfish).  Use
69       out-of-range key lengths (and this class) only for compatibility or
70       cryptanalytic reasons.
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CLASS METHODS

73       Crypt::Eksblowfish::Uklblowfish->blocksize
74           Returns 8, indicating the Blowfish block size of 8 octets.  This
75           method may be called on either the class or an instance.
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77       Crypt::Eksblowfish::Uklblowfish->keysize
78           Returns 0, indicating that the key size is variable.  This
79           situation is handled specially by "Crypt::CBC".
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CONSTRUCTOR

82       Crypt::Eksblowfish::Uklblowfish->new(KEY)
83           Performs key setup on a new instance of the Blowfish algorithm,
84           returning the keyed state.  The KEY may be any length from 1 octet
85           to 72 octets inclusive.
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METHODS

88       $cipher->blocksize
89           Returns 8, indicating the Blowfish block size of 8 octets.  This
90           method may be called on either the class or an instance.
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92       $cipher->encrypt(PLAINTEXT)
93           PLAINTEXT must be exactly eight octets.  The block is encrypted,
94           and the ciphertext is returned.
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96       $cipher->decrypt(CIPHERTEXT)
97           CIPHERTEXT must be exactly eight octets.  The block is decrypted,
98           and the plaintext is returned.
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100       $cipher->p_array
101       $cipher->s_boxes
102           These methods extract the subkeys from the keyed cipher.  This is
103           not required in ordinary operation.  See the superclass
104           Crypt::Eksblowfish::Subkeyed for details.
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106       $cipher->is_weak
107           This method checks whether the cipher has been keyed with a weak
108           key.  It may be desired to avoid using weak keys.  See the
109           superclass Crypt::Eksblowfish::Subkeyed for details.
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111           This method does not detect any cryptographic weaknesses that might
112           result from the related-key properties and other features of
113           overlong keys.
114

SEE ALSO

116       Crypt::Eksblowfish::Blowfish
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AUTHOR

119       Eksblowfish guts originally by Solar Designer (solar at openwall.com).
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121       Modifications and Perl interface by Andrew Main (Zefram)
122       <zefram@fysh.org>.
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125       Copyright (C) 2006, 2007, 2008, 2009, 2010, 2011 Andrew Main (Zefram)
126       <zefram@fysh.org>
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128       The original Eksblowfish code (in the form of crypt()) from which this
129       module is derived is in the public domain.  It may be found at
130       <http://www.openwall.com/crypt/>.
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LICENSE

133       This module is free software; you can redistribute it and/or modify it
134       under the same terms as Perl itself.
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138perl v5.30.1                      2020-01-29Crypt::Eksblowfish::Uklblowfish(3)
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