Crypt::Eksblowfish::Family(3pm) 			User Contributed Perl Documentation			   Crypt::Eksblowfish::Family(3pm)

NAME

       Crypt::Eksblowfish::Family - Eksblowfish cipher family

SYNOPSIS

	       use Crypt::Eksblowfish::Family;

	       $family = Crypt::Eksblowfish::Family->new_family(8, $salt);

	       $cost = $family->cost;
	       $salt = $family->salt;
	       $block_size = $family->blocksize;
	       $key_size = $family->keysize;
	       $cipher = $family->new($key);

DESCRIPTION

       An object of this class represents an Eksblowfish cipher family.  It contains the family parameters (cost and salt), and if combined with a
       key it yields an encryption function.  See Crypt::Eksblowfish for discussion of the Eksblowfish algorithm.

       It is intended that an object of this class can be used in situations such as the "-cipher" parameter to "Crypt::CBC".  Normally that
       parameter is the name of a class, such as "Crypt::Rijndael", where the class implements a block cipher algorithm.  The class provides a
       "new" constructor that accepts a key.  In the case of Eksblowfish, the key alone is not sufficient.  An Eksblowfish family fills the role
       of block cipher algorithm.  Therefore a family object is used in place of a class name, and it is the family object the provides the "new"
       constructor.

   Crypt::CBC
       "Crypt::CBC" itself has a problem, with the result that this class can no longer be used with it in the manner originally intended.

       When this class was originally designed, it worked with "Crypt::CBC" as described above: an object of this class would be accepted by
       "Crypt::CBC" as a cipher algorithm, and "Crypt::CBC" would happily supply it with a key and encrypt using the resulting cipher object.
       "Crypt::CBC" didn't realise it was dealing with a family object, however, and there was some risk that a future version might accidentally
       squash the object into a string, which would be no use.	In the course of discussion about regularising the use of cipher family objects,
       the author of "Crypt::CBC" got hold of the wrong end of the stick, and ended up changing "Crypt::CBC" in a way that totally breaks this
       usage, rather than putting it on a secure footing.

       The present behaviour of "Crypt::CBC" is that if an object (rather than a class name) is supplied as the "-cipher" parameter then it has a
       completely different meaning from usual.  In this case, the object supplied is used as the keyed cipher, rather than as a cipher algorithm
       which must be given a key.  This bypasses all of "Crypt::CBC"'s usual keying logic, which can hash and salt a passphrase to generate the
       key.  It is arguably a useful feature, but it's a gross abuse of the "-cipher" parameter and a severe impediment to the use of family-keyed
       cipher algorithms.

       This class now provides a workaround.  For the benefit of "Crypt::CBC", and any other crypto plumbing that requires a keyable cipher
       algorithm to look like a Perl class (rather than an object), a family object of this class can in fact be reified as a class of its own.
       See the method "as_class".

CONSTRUCTOR

       Crypt::Eksblowfish::Family->new_family(COST, SALT)
	   Creates and returns an object representing the Eksblowfish cipher family specified by the parameters.  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.

METHODS

       $family->cost
	   Extracts and returns the cost parameter.

       $family->salt
	   Extracts and returns the salt parameter.

       $family->blocksize
	   Returns 8, indicating the Eksblowfish block size of 8 octets.

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

       $family->new(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 object returned is of class "Crypt::Eksblowfish"; see Crypt::Eksblowfish for the encryption and decryption
	   methods.

	   Note that this method is called on a family object, not on the class "Crypt::Eksblowfish::Family".

       $family->encrypt
	   This method nominally exists, to satisfy "Crypt::CBC".  It can't really be used: it doesn't make any sense.

       $family->as_class
	   Generates and returns (the name of) a Perl class that behaves as a keyable cipher algorithm identical to this Eksblowfish cipher
	   family.  The same methods that can be called as instance methods on $family can be called as class methods on the generated class.

	   You should prefer to use the family object directly wherever you can.  Aside from being a silly indirection, the classes generated by
	   this method cannot be garbage-collected.  This method exists only to cater to "Crypt::CBC", which requires a keyable cipher algorithm
	   to look like a Perl class, and won't operate correctly on one that looks like an object.

SEE ALSO

       Crypt::CBC, Crypt::Eksblowfish

AUTHOR

       Andrew Main (Zefram) <zefram@fysh.org>

COPYRIGHT

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

LICENSE

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

perl v5.14.2							    2011-11-15					   Crypt::Eksblowfish::Family(3pm)