![]() All involved some aspect of the previous positions of the machine's wheels. These were of four different types and were called "Limitations" at Bletchley Park. On all but the earliest machines, there was an additional factor that played into the moving on or not of the psi wheels. This was a product of XOR-ing the 5-bit character generated by the right hand five wheels, the chi ( χ 37 and the psi wheels stayed still. The key stream was generated by ten of the twelve wheels. the system implemented a symmetric-key algorithm. ![]() At the receiving end, an identically configured machine produced the same key stream which was combined with the ciphertext to produce the plaintext, i. The key stream was combined with the plaintext to produce the ciphertext at the transmitting end using the exclusive or (XOR) function. The Lorenz SZ cipher attachments implemented a Vernam stream cipher, using a complex array of twelve wheels that delivered what should have been a cryptographically secure pseudorandom number as a key stream. German Tunny machines The Lorenz SZ machines had 12 wheels each with a different number of cams (or "pins"). The result is an outstanding contribution to cryptanalytic science. Each could have been overemphasised or underemphasised to the detriment of the solutions a remarkable fact is that the fusion of the elements has been apparently in perfect proportion. Each of these has been a necessary factor. Small, a cryptanalyst from the US Army Signal Corps who was seconded to Bletchley Park and worked on Tunny, said in his December 1944 report back to Arlington Hall that:ĭaily solutions of Fish messages at GC&CS reflect a background of British mathematical genius, superb engineering ability, and solid common sense. The problems of decrypting Tunny messages led to the development of " Colossus", the world's first electronic, programmable digital computer, ten of which were in use by the end of the war, by which time some 90% of selected Tunny messages were being decrypted at Bletchley Park. Unlike Enigma, no physical machine reached allied hands until the very end of the war in Europe, long after wholesale decryption had been established. ![]() Īs with the entirely separate cryptanalysis of the Enigma, it was German operational shortcomings that allowed the initial diagnosis of the system, and a way into decryption. " Tunny" (tunafish) was the name given to the first non-Morse link, and it was subsequently used for the cipher machines and their traffic. īletchley Park decrypts of messages enciphered with the Enigma machines revealed that the Germans called one of their wireless teleprinter transmission systems "Sägefisch" (sawfish), which led British cryptographers to refer to encrypted German radiotelegraphic traffic as " Fish". These machines were subsequently discovered to be the Lorenz SZ (SZ for Schlüssel-Zusatz, meaning "cipher attachment") for the army, the Siemens and Halske T52 for the air force and the Siemens T43, which was little used and never broken by the Allies. įor its high-level secret messages, the German armed services enciphered each character using various online Geheimschreiber (secret writer) stream cipher machines at both ends of a telegraph link using the 5-bit International Telegraphy Alphabet No. Decrypts of this traffic became an important source of " Ultra" intelligence, which contributed significantly to Allied victory. These were intercepted non- Morse radio transmissions that had been enciphered by the Lorenz SZ teleprinter rotor stream cipher attachments. The British Government Code and Cypher School (GC&CS) at Bletchley Park decrypted many communications between the Oberkommando der Wehrmacht (OKW, German High Command) in Berlin and their army commands throughout occupied Europe, some of which were signed "Adolf Hitler, Führer". Ten Colossi in use, first sight of a Tunny machine.Ĭryptanalysis of the Lorenz cipher was the process that enabled the British to read high-level German army messages during World War II.
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