May 26, 2018

Perl module for the Eksblowfish block cipher

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.

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.

This distribution also includes an implementation of “bcrypt”, the Unix crypt password hashing algorithm based on Eksblowfish.

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