NAME

       Crypt::Eksblowfish::Uklblowfish - Blowfish cipher with unrestricted key length

SYNOPSIS

               use Crypt::Eksblowfish::Uklblowfish;

               $block_size = Crypt::Eksblowfish::Uklblowfish->blocksize;
               $key_size = Crypt::Eksblowfish::Uklblowfish->keysize;

               $cipher = Crypt::Eksblowfish::Uklblowfish->new($key);

               $block_size = $cipher->blocksize;
               $ciphertext = $cipher->encrypt($plaintext);
               $plaintext = $cipher->decrypt($ciphertext);

               $p_array = $cipher->p_array;
               $s_boxes = $cipher->s_boxes;
               if($cipher->is_weak) { ...

DESCRIPTION

       An object of this type encapsulates a keyed instance of the Blowfish block cipher, ready
       to encrypt and decrypt.  However, if you're looking for an implementation of Blowfish you
       most likely want Crypt::Eksblowfish::Blowfish.  This class differs from the standard
       Blowfish in that it accepts some keys that Blowfish officially does not permit.

       Blowfish is a symmetric cipher algorithm designed by Bruce Schneier in 1993.  It operates
       on 64-bit blocks, and takes a variable-length key.  Officially the key can vary from 32
       bits (4 octets) to 448 bits (56 octets) in increments of 8 bits (1 octet).  In fact the
       algorithm can easily operate on a key of any number of octets from 1 (8 bits) to 72 (576
       bits).  Some implementations don't enforce the official key length limits, and so for
       compatibility it is sometimes necessary to handle a Blowfish key of a prohibited length.
       That is what this class is for.  The "Ukl" in the name stands for "unrestricted key
       length".

       Using a very short key is generally a bad idea because there aren't very many keys of that
       length and so it's easy for an attacker to try them all.  The official 32-bit minimum for
       Blowfish was already far too short for serious security at the time that Blowfish was
       designed.  (A machine to crack 56-bit DES keys by brute force in a few days each was
       publicly built only five years later.)  Do not base your security on the secrecy of a
       short key.

       Using overlong keys has more interesting effects, which depend on internal features of
       Blowfish.  When the key exceeds 64 octets (512 bits), varying key bits past that length
       results in subkeys which have predictable relationships.  There is also some possibility
       of equivalent keys when the keys exceed 64 octets and differ only in the first 8 octets
       (64 bits).  These phenomena have not been extensively studied in the open literature, so
       it is difficult to judge the degree of cryptographic weakness that results from them.  It
       is clear that beyond some length Blowfish keys do not have as much strength as their
       length would suggest, and it is possible that overlong keys have specific weaknesses that
       render them weaker than shorter keys.  If choosing a key for security, it is advised to
       stay within the official length limit of 56 octets.

       In summary: using Blowfish keys of officially-unsupported lengths causes security
       problems.  If you are using Blowfish for security, and have the choice, use a key of an
       officially-supported length (and a standard implementation such as
       Crypt::Eksblowfish::Blowfish).  Use out-of-range key lengths (and this class) only for
       compatibility or cryptanalytic reasons.

CLASS METHODS

       Crypt::Eksblowfish::Uklblowfish->blocksize
           Returns 8, indicating the Blowfish block size of 8 octets.  This method may be called
           on either the class or an instance.

       Crypt::Eksblowfish::Uklblowfish->keysize
           Returns 0, indicating that the key size is variable.  This situation is handled
           specially by "Crypt::CBC".

CONSTRUCTOR

       Crypt::Eksblowfish::Uklblowfish->new(KEY)
           Performs key setup on a new instance of the Blowfish algorithm, returning the keyed
           state.  The KEY may be any length from 1 octet to 72 octets inclusive.

METHODS

       $cipher->blocksize
           Returns 8, indicating the Blowfish block size of 8 octets.  This method may be called
           on either the class or an instance.

       $cipher->encrypt(PLAINTEXT)
           PLAINTEXT must be exactly eight octets.  The block is encrypted, and the ciphertext is
           returned.

       $cipher->decrypt(CIPHERTEXT)
           CIPHERTEXT must be exactly eight octets.  The block is decrypted, and the plaintext is
           returned.

       $cipher->p_array
       $cipher->s_boxes
           These methods extract the subkeys from the keyed cipher.  This is not required in
           ordinary operation.  See the superclass Crypt::Eksblowfish::Subkeyed for details.

       $cipher->is_weak
           This method checks whether the cipher has been keyed with a weak key.  It may be
           desired to avoid using weak keys.  See the superclass Crypt::Eksblowfish::Subkeyed for
           details.

           This method does not detect any cryptographic weaknesses that might result from the
           related-key properties and other features of overlong keys.

SEE ALSO

       Crypt::Eksblowfish::Blowfish

AUTHOR

       Eksblowfish guts originally by Solar Designer (solar at openwall.com).

       Modifications and Perl interface by Andrew Main (Zefram) <zefram@fysh.org>.

COPYRIGHT

       Copyright (C) 2006, 2007, 2008, 2009, 2010, 2011 Andrew Main (Zefram) <zefram@fysh.org>

       The original Eksblowfish code (in the form of crypt()) from which this module is derived
       is in the public domain.  It may be found at <http://www.openwall.com/crypt/>.

LICENSE

       This module is free software; you can redistribute it and/or modify it under the same
       terms as Perl itself.