Lorenz cipher

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The Lorenz SZ40, SZ42a, and SZ42b were German rotor stream cipher machines used by the German Army during World War II. They were developed by C. Lorenz AG in Berlin. The model name SZ is derived from Schlüssel-Zusatz, meaning cipher attachment. The machines implemented a Vernam stream cipher. British cryptanalysts, who referred to encrypted German teleprinter traffic as Fish, dubbed the machine and its traffic Tunny (meaning 'tunafish') and deduced its logical structure three years before they saw such a machine. The SZ machines were in-line attachments to standard teleprinters. An experimental link using SZ40 machines was started in June 1941. The enhanced SZ42 machines were brought into substantial use from mid-1942 onwards for high-level communications between the German High Command in Wünsdorf close to Berlin, and Army Commands throughout occupied Europe. The more advanced SZ42A came into routine use in February 1943 and the SZ42B in June 1944. Radioteletype (RTTY) rather than land...

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