John the Ripper – password cracker
John the Ripper is free and Open Source software, distributed primarily in source code form. If you would rather use a commercial product tailored for your specific operating system, please consider John the Ripper Pro, which is distributed primarily in the form of “native” packages for the target operating systems and in general is meant to be easier to install and use while delivering optimal performance.
Official free versions
This version integrates lots of contributed patches adding GPU support (CUDA and OpenCL), support for a hundred of additional hash and cipher types (including popular ones such as NTLM, raw MD5, etc., and even things such as encrypted OpenSSH private keys, ZIP and RAR archives, PDF files, etc.), as well as some optimizations and features. Unfortunately, its overall quality is lower than the official version’s. Requires OpenSSL 0.9.7 or newer. There are unofficial binary builds (by John the Ripper user community members) for Windows, Linux, Solaris, and Mac OS X.