Description:

John the Ripper is a fast password cracker, currently available for many
flavors of Unix (11 are officially supported, not counting different
architectures), DOS, Win32, and BeOS. Its primary purpose is to detect
weak Unix passwords, but a number of other hash types are supported as
well.

NOTE: If you want to recompile specifically for your CPU, you can
rebuild RPM with following option:

rpmbuild --define='extra_cflags -march=athlon' \
--rebuild john*.src.rpm

For x86 or x86_64 CPUs, if you don't want optimization or
native 64 bit support, you can use '--without optimize' option.