Crypt::Eksblowfish::Family - Eksblowfish cipher 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);
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
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" 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
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".
- 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
- Extracts and returns the cost parameter.
- Extracts and returns the salt parameter.
- Returns 8, indicating the Eksblowfish block size of 8
- Returns 0, indicating that the key size is variable. This
situation is handled specially by "Crypt::CBC".
- 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
- This method nominally exists, to satisfy
"Crypt::CBC". It can't really be used: it doesn't make any
- 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
Andrew Main (Zefram) <firstname.lastname@example.org>
Copyright (C) 2006, 2007, 2008, 2009, 2010, 2011 Andrew Main (Zefram)
This module is free software; you can redistribute it and/or modify it under the
same terms as Perl itself.