This site is moving to https://jorgicor.niobe.org/aenig4 and will eventually disappear. Please, update your links and bookmarks.
aenig4 emulates the Enigma M4 cipher machine used by the U-Boot division of the German Navy during World War II. It can be used as well to emulate the Enigma I machine (M1, M2, M3).
aenig4 is free software.