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