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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'' was derived from ''Schlüsselzusatz'', meaning ''cipher attachment''. The instruments implemented a Vernam stream cipher. British cryptographers, who referred to encrypted German teleprinter traffic as ''Fish'', dubbed the machine and its traffic ''Tunny''. 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. Wireless telegraphy (WT) rather than land-line circuits was used for this traffic.〔 of ''German Tunny''〕 These non-Morse (NoMo) messages were picked up by Britain's Y-stations at Knockholt and Denmark Hill and sent to Government Code and Cypher School at Bletchley Park (BP). Some were deciphered using hand methods before the process was partially automated, first with Robinson machines and then with the Colossus computers. The deciphered Lorenz messages made one of the most significant contributions to British ''Ultra'' military intelligence and to Allied victory in Europe, due to the high-level strategic nature of the information that was gained from Lorenz decrypts.〔http://cs.stanford.edu/people/eroberts/courses/soco/projects/colossus/history.html〕 ==The Vernam cipher== (詳細はGilbert Vernam was an AT&T Bell Labs research engineer who, in 1917, invented a cipher system that used the Boolean "exclusive or" (XOR) function, symbolized by ⊕. This is represented by the following "truth table", where 1 represents "true" and 0 represents "false". Other names for this function are: Not equal (NEQ), modulo 2 addition (without 'carry') and modulo 2 subtraction (without 'borrow'). Vernam's cipher is a Symmetric-key algorithm, i.e. the same key is used both to encipher plaintext to produce the ciphertext and to decipher ciphertext to yield the original plaintext: ::::Plaintext ⊕ Key = Ciphertext and: ::::Ciphertext ⊕ Key = Plaintext This produces the essential reciprocity that allows the same machine with the same settings to be used for both enciphering and deciphering. Vernam's idea was to use conventional telegraphy practice with a paper tape of the plaintext combined with a paper tape of the key. Each key tape would have been unique (a one-time tape), but generating and distributing such tapes presented considerable practical difficulties. In the 1920s four men in different countries invented rotor cipher machines to produce a key stream to act instead of a tape. The 1940 Lorenz SZ40/42 was one of these.〔 of ''German Tunny''〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Lorenz cipher」の詳細全文を読む スポンサード リンク
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