The Enigma project was a WW2 allied effort to crack German codes encrypted on the mechanical computing machine of the same name. More than 60 years later, some of the messages remain unencoded. There's a project underway to crack them.

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.