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NAME |
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Crypt::Twofish2 - Crypt::CBC compliant Twofish encryption module |
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SYNOPSIS |
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use Crypt::Twofish2; |
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# keysize() is 32, but 24 and 16 are also possible |
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# blocksize() is 16 |
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$cipher = new Crypt::Twofish2 "a" x 32, Crypt::Twofish2::MODE_CBC; |
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$crypted = $cipher->encrypt($plaintext); |
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# - OR - |
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$plaintext = $cipher->decrypt($crypted); |
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DESCRIPTION |
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This module implements thw twofish cipher in a less braindamaged (read: |
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slow and ugly) way than the existing "Crypt::Twofish" module. |
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Although it is "Crypt::CBC" compliant you usually gain nothing by using |
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that module (except generality), since "Crypt::Twofish2" can work in |
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either ECB or CBC mode. |
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keysize |
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Returns the keysize, which is 32 (bytes). The Twofish2 cipher |
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actually supports keylengths of 16, 24 or 32 bytes, but there is no |
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way to communicate this to "Crypt::CBC". |
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blocksize |
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The blocksize for Twofish2 is 16 bytes (128 bits), which is somewhat |
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unique. It is also the reason I need this module myself ;) |
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$cipher = new $key [, $mode] |
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Create a new "Crypt::Twofish2" cipher object with the given key |
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(which must be 128, 192 or 256 bits long). The additional "$mode" |
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argument is the encryption mode, either "MODE_ECB" (electronic |
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cookbook mode, the default), "MODE_CBC" (cipher block chaining, the |
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same that "Crypt::CBC" does) or "MODE_CFB1" (1-bit cipher feedback |
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mode). |
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ECB mode is very insecure (read a book on cryptography if you don't |
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know why!), so you should probably use CBC mode. CFB1 mode is not |
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tested and is most probably broken, so do not try to use it. |
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In ECB mode you can use the same cipher object to encrypt and |
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decrypt data. However, every change of "direction" causes an |
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internal reordering of key data, which is quite slow, so if you want |
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ECB mode and encryption/decryption at the same time you should |
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create two seperate "Crypt::Twofish2" objects with the same key. |
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In CBC mode you have to use seperate objects for |
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encryption/decryption in any case. |
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The "MODE_*"-constants are not exported by this module, so you must |
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specify them as "Crypt::Twofish2::MODE_CBC" etc. (sorry for that). |
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$cipher->encrypt($data) |
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Encrypt data. The size of "$data" must be a multiple of "blocksize" |
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(16 bytes), otherwise this function will croak. Apart from that, it |
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can be of (almost) any length. |
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$cipher->decrypt($data) |
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The pendant to "encrypt" in that it *de*crypts data again. |
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SEE ALSO |
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the Crypt::CBC manpage, the Crypt::Twofish manpage. |
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BUGS |
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Should EXPORT or EXPORT_OK the MODE constants. |
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The testsuite does not check wether the encrypted valued are correct. |
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There should be a way to access initial IV contents :( |
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Although I tried to make the original twofish code portable, I can't say |
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how much I did succeed. The code tries to be portable itself, and I hope |
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I got the endianness issues right. The code is also copyright |
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Counterpane Systems, no license accompanied it, so using it might |
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actually be illegal ;) |
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AUTHOR |
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Marc Lehmann <pcg@goof.com> |
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http://www.goof.com/pcg/marc/ |
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The actualy twofish encryption is written in horribly microsoft'ish looking |
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almost ansi-c by Doug Whiting. |
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