John the Ripper is a fast password cracker, currently available for many
flavors of Unix (11 are officially supported, not counting different
architectures), Windows, DOS, BeOS, and OpenVMS. Its primary purpose is to
detect weak Unix passwords. Besides several crypt(3) password hash types
most commonly found on various Unix flavors, supported out of the box are
Kerberos AFS and Windows NT/2000/XP/2003 LM hashes, plus several more with
contributed patches.

SlackBuild contain updated version of Ryan Lim's patch for john the
ripper to support MPI. MPI allows you to use multiple processors on a
single system, or a cluster of systems for cracking passwords using
john the ripper. You need in this case OpenMPI, also available from
the SlackBuilds.org repository. But the author of the program does not
recommend use any hacks for parallel processing (see in the bottom of page
http://www.openwall.com/lists/john-users/2005/08/24/4). Use it at own risk!

Slackbuild contain also jambo patch. The jumbo patch enables processing
of many password hash types and ciphers that are not supported by the
official JtR. Both patches are disabled by default.

Note this will not build in parallel, set MAKEFLAGS="-j1" if you have
problems.