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.

perl v5.38.2                                       2024-04-01               Crypt::Eksblowfish::Uklblowfish(3pm)