http://www.enigmaathome.net/



Enigma@Home is a wrapper between BOINC and Stefan Krah's M4 Project. 'The M4 Project is an effort to break 3 original Enigma messages with the help of distributed computing. The signals were intercepted in the North Atlantic in 1942 and are believed to be unbroken.' [read more] You can participate by downloading and running a free program on your computer.