Messages sent over the wireless in the World War II era could be intercepted so the Germans used a cryptographic device. On the surface, the Enigma cipher machine looked like a regular typewriter, but it wasn't. A keyboard was linked to rotors, powered by an electric current, which transposed every keystroke several times. Corresponding messages went out in Morse code and required keys, which changed daily, to decipher -- get it? "De-cipher. " Which is exactly what the Allies did, cracking a code the Germans thought was unbreakable.