“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. Ralph Erskine has presented the intercepts in a letter to the journal Cryptologia. The signals were presumably enciphered with the four rotor Enigma M4 – hence the name of the project.
This project has officially started as of January 9th, 2006. You can help out by donating idle time of your computer to the project.”
I’m having trouble downloading the client from their site, so, since it’s (mostly) GPL-licenced, I’m hosting version 0.73.3 of the Windows XP Pro client here.