NAME

       Crypt::Eksblowfish - the Eksblowfish block cipher

SYNOPSIS

               use Crypt::Eksblowfish;

               $block_size = Crypt::Eksblowfish->blocksize;

               $cipher = Crypt::Eksblowfish->new(8, $salt, $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 Eksblowfish block cipher,
       ready to encrypt and decrypt.

       Eksblowfish is a variant of the Blowfish cipher, modified to make the key setup very
       expensive.  ("Eks" stands for "expensive key schedule".)  This doesn't make it
       significantly cryptographically stronger, but is intended to hinder brute-force attacks.
       It also makes it unsuitable for any application requiring key agility.  It was designed by
       Niels Provos and David Mazieres for password hashing in OpenBSD.  See
       Crypt::Eksblowfish::Bcrypt for the hash algorithm.  See Crypt::Eksblowfish::Blowfish for
       the unmodified Blowfish cipher.

       Eksblowfish is a parameterised (family-keyed) cipher.  It takes a cost parameter that
       controls how expensive the key scheduling is.  It also takes a family key, known as the
       "salt".  Cost and salt parameters together define a cipher family.  Within each family, a
       key determines an encryption function in the usual way.  See Crypt::Eksblowfish::Family
       for a way to encapsulate an Eksblowfish cipher family.

CLASS METHODS

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

CONSTRUCTOR

       Crypt::Eksblowfish->new(COST, SALT, KEY)
           Performs key setup on a new instance of the Eksblowfish algorithm, returning the keyed
           state.  The KEY may be any length from 1 octet to 72 octets inclusive.  The SALT is a
           family key, and must be exactly 16 octets.  COST is an integer parameter controlling
           the expense of keying: the number of operations in key setup is proportional to
           2^COST.  All three parameters influence all the subkeys; changing any of them produces
           a different encryption function.

           Due to the mandatory family-keying parameters (COST and SALT), this constructor does
           not match the interface expected by "Crypt::CBC" and similar crypto plumbing modules.
           To use Eksblowfish with them it is necessary to have an object that encapsulates a
           cipher family and provides a constructor that takes only a key argument.  That
           facility is supplied by "Crypt::Eksblowfish::Family".

METHODS

       $cipher->blocksize
           Returns 8, indicating the Eksblowfish 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.

SEE ALSO

       Crypt::Eksblowfish::Bcrypt, Crypt::Eksblowfish::Blowfish, Crypt::Eksblowfish::Family,
       Crypt::Eksblowfish::Subkeyed,
       <http://www.usenix.org/events/usenix99/provos/provos_html/node4.html>

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.