Crypt::Eksblowfish::Uklblowfish man page on Fedora

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Crypt::Eksblowfish::UkUserwContributed Perl Crypt::Eksblowfish::Uklblowfish(3)

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 v5.14.1			  2011-06-21Crypt::Eksblowfish::Uklblowfish(3)
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