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.