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/cvs/Crypt-Twofish2/Twofish2.pm
Revision: 1.6
Committed: Sun Aug 1 18:09:47 2021 UTC (3 years, 3 months ago) by root
Branch: MAIN
CVS Tags: rel-1_03, HEAD
Changes since 1.5: +1 -1 lines
Log Message:
1.03

File Contents

# User Rev Content
1 root 1.1 =head1 NAME
2    
3     Crypt::Twofish2 - Crypt::CBC compliant Twofish encryption module
4    
5     =head1 SYNOPSIS
6    
7     use Crypt::Twofish2;
8    
9     # keysize() is 32, but 24 and 16 are also possible
10     # blocksize() is 16
11    
12     $cipher = new Crypt::Twofish2 "a" x 32, Crypt::Twofish2::MODE_CBC;
13    
14     $crypted = $cipher->encrypt($plaintext);
15     # - OR -
16     $plaintext = $cipher->decrypt($crypted);
17    
18     =head1 DESCRIPTION
19    
20     This module implements the twofish cipher in a less braindamaged (read:
21     slow and ugly) way than the existing C<Crypt::Twofish> module.
22    
23     Although it is C<Crypt::CBC> compliant you usually gain nothing by using
24     that module (except generality, which is often a good thing), since
25     C<Crypt::Twofish2> can work in either ECB or CBC mode itself.
26    
27     =over 4
28    
29     =cut
30    
31     package Crypt::Twofish2;
32    
33 root 1.5 use XSLoader;
34 root 1.1
35 root 1.6 $VERSION = '1.03';
36 root 1.1
37 root 1.5 XSLoader::load __PACKAGE__, $VERSION;
38 root 1.1
39     =item keysize
40    
41     Returns the keysize, which is 32 (bytes). The Twofish2 cipher actually
42     supports keylengths of 16, 24 or 32 bytes, but there is no way to
43     communicate this to C<Crypt::CBC>.
44    
45     =item blocksize
46    
47     The blocksize for Twofish2 is 16 bytes (128 bits), which is somewhat
48     unique. It is also the reason I need this module myself ;)
49    
50     =item $cipher = new $key [, $mode]
51    
52     Create a new C<Crypt::Twofish2> cipher object with the given key (which
53     must be 128, 192 or 256 bits long). The additional C<$mode> argument is
54     the encryption mode, either C<MODE_ECB> (electronic cookbook mode, the
55     default), C<MODE_CBC> (cipher block chaining, the same that C<Crypt::CBC>
56     does) or C<MODE_CFB1> (1-bit cipher feedback mode).
57    
58     ECB mode is very insecure (read a book on cryptography if you don't know
59     why!), so you should probably use CBC mode. CFB1 mode is not tested and is
60     most probably broken, so do not try to use it.
61    
62     In ECB mode you can use the same cipher object to encrypt and decrypt
63     data. However, every change of "direction" causes an internal reordering
64     of key data, which is quite slow, so if you want ECB mode and
65     encryption/decryption at the same time you should create two seperate
66     C<Crypt::Twofish2> objects with the same key.
67    
68     In CBC mode you have to use seperate objects for encryption/decryption in
69     any case.
70    
71     The C<MODE_*>-constants are not exported by this module, so you must
72     specify them as C<Crypt::Twofish2::MODE_CBC> etc. (sorry for that).
73    
74     =item $cipher->encrypt($data)
75    
76     Encrypt data. The size of C<$data> must be a multiple of C<blocksize> (16
77     bytes), otherwise this function will croak. Apart from that, it can be of
78     (almost) any length.
79    
80     =item $cipher->decrypt($data)
81    
82     The pendant to C<encrypt> in that it I<de>crypts data again.
83    
84     =back
85    
86     =head1 SEE ALSO
87    
88     L<Crypt::CBC>, L<Crypt::Twofish>.
89    
90     =head1 BUGS
91    
92     Should EXPORT or EXPORT_OK the MODE constants.
93    
94     There should be a way to access initial IV contents :(
95    
96     Although I tried to make the original twofish code portable, I can't say
97     how much I did succeed. The code tries to be portable itself, and I hope
98     I got the endianness issues right. The code is also copyright Counterpane
99     Systems, no license accompanied it, so using it might actually be illegal
100     ;)
101    
102     I also cannot guarantee for security, but the module is used quite a bit,
103     so there are no obvious bugs left.
104    
105     =head1 AUTHOR
106    
107 root 1.4 Marc Lehmann <schmorp@schmorp.de>
108 root 1.3 http://home.schmorp.de/
109 root 1.1
110     The actual twofish encryption is written in horribly microsoft'ish looking
111     almost ansi-c by Doug Whiting.
112    
113     =cut
114    
115     1;
116