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/cvs/Crypt-Twofish2/Twofish2.pm
Revision: 1.4
Committed: Thu Mar 3 17:22:20 2005 UTC (19 years, 9 months ago) by root
Branch: MAIN
Changes since 1.3: +2 -2 lines
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# 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     require DynaLoader;
34    
35 root 1.4 $VERSION = '1.01';
36 root 1.1 @ISA = qw/DynaLoader/;
37    
38     bootstrap Crypt::Twofish2 $VERSION;
39    
40     =item keysize
41    
42     Returns the keysize, which is 32 (bytes). The Twofish2 cipher actually
43     supports keylengths of 16, 24 or 32 bytes, but there is no way to
44     communicate this to C<Crypt::CBC>.
45    
46     =item blocksize
47    
48     The blocksize for Twofish2 is 16 bytes (128 bits), which is somewhat
49     unique. It is also the reason I need this module myself ;)
50    
51     =item $cipher = new $key [, $mode]
52    
53     Create a new C<Crypt::Twofish2> cipher object with the given key (which
54     must be 128, 192 or 256 bits long). The additional C<$mode> argument is
55     the encryption mode, either C<MODE_ECB> (electronic cookbook mode, the
56     default), C<MODE_CBC> (cipher block chaining, the same that C<Crypt::CBC>
57     does) or C<MODE_CFB1> (1-bit cipher feedback mode).
58    
59     ECB mode is very insecure (read a book on cryptography if you don't know
60     why!), so you should probably use CBC mode. CFB1 mode is not tested and is
61     most probably broken, so do not try to use it.
62    
63     In ECB mode you can use the same cipher object to encrypt and decrypt
64     data. However, every change of "direction" causes an internal reordering
65     of key data, which is quite slow, so if you want ECB mode and
66     encryption/decryption at the same time you should create two seperate
67     C<Crypt::Twofish2> objects with the same key.
68    
69     In CBC mode you have to use seperate objects for encryption/decryption in
70     any case.
71    
72     The C<MODE_*>-constants are not exported by this module, so you must
73     specify them as C<Crypt::Twofish2::MODE_CBC> etc. (sorry for that).
74    
75     =item $cipher->encrypt($data)
76    
77     Encrypt data. The size of C<$data> must be a multiple of C<blocksize> (16
78     bytes), otherwise this function will croak. Apart from that, it can be of
79     (almost) any length.
80    
81     =item $cipher->decrypt($data)
82    
83     The pendant to C<encrypt> in that it I<de>crypts data again.
84    
85     =back
86    
87     =head1 SEE ALSO
88    
89     L<Crypt::CBC>, L<Crypt::Twofish>.
90    
91     =head1 BUGS
92    
93     Should EXPORT or EXPORT_OK the MODE constants.
94    
95     There should be a way to access initial IV contents :(
96    
97     Although I tried to make the original twofish code portable, I can't say
98     how much I did succeed. The code tries to be portable itself, and I hope
99     I got the endianness issues right. The code is also copyright Counterpane
100     Systems, no license accompanied it, so using it might actually be illegal
101     ;)
102    
103     I also cannot guarantee for security, but the module is used quite a bit,
104     so there are no obvious bugs left.
105    
106     =head1 AUTHOR
107    
108 root 1.4 Marc Lehmann <schmorp@schmorp.de>
109 root 1.3 http://home.schmorp.de/
110 root 1.1
111     The actual twofish encryption is written in horribly microsoft'ish looking
112     almost ansi-c by Doug Whiting.
113    
114     =cut
115    
116     1;
117