Geheimschreiber

A German word meaning "secret writer," Geheimschreiber was the name of a cipher machine that produced an encrypted punched tape, which could be fed through a teleprinter for transmission via radio lines. The transmitting stations had first been detected by British intelligence in 1940, and by 1942 most had been identified. Interception and decryption operations began in mid-1942 and presented an even greater challenge than decrypting messages produced by the more famous Enigma cipher and machine because the Geheimschreiber used more encryption rotors: 10 as opposed to the three to five rotors of the Enigma. Indeed, it required the invention of some of the first practical computers—an experimental machine dubbed "Heath Robinson," followed by the more celebrated "Colossus I" and "Colossus II"—to perform the work. Colossus II is considered by some historians of computer science to be the first genuine fully electronic computer. It came on line on June 6, 1944, the very day of the Normandy landings (D-day), and was invaluable in its yield of important intelligence through the end of the war in Europe. Geheimschreiber decrypts were code named "FISH" by the Allies.