Crypt::Eksblowfish(3pm)
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 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.