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/cvs/Crypt-Twofish2/Twofish2.pm
Revision: 1.1
Committed: Sat Sep 6 22:10:54 2003 UTC (21 years, 3 months ago) by root
Branch: MAIN
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File Contents

# Content
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 $VERSION = 0.06;
36 @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 Marc Lehmann <pcg@goof.com>
109 http://www.goof.com/pcg/marc/
110
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