Cryptanalysis of the Lorenz cipher was the process that enabled the British to read high-level German army messages during World War II. The British Government Code and Cypher School at Bletchley Park
Cams on wheels 9 and 10 showing their raised (active) and lowered (inactive) positions. An active cam reversed the value of a bit (•→x and x→•).
A Lorenz SZ42 cipher machine with its covers removed at The National Museum of Computing on Bletchley Park
A rebuilt British Tunny at the National Museum of Computing, Bletchley Park. It emulated the functions of the Lorenz SZ40/42, producing printed cleartext from ciphertext input.
A Mark 2 Colossus computer. The Wren operators are (left to right) Dorothy Du Boisson and Elsie Booker. The slanted control panel on the left was used to set the pin patterns on the Lorenz. The "bedstead" paper tape transport is on the right.
Colossus computer
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Colossus was a set of computers developed by British codebreakers in the years 1943–1945 to help in the cryptanalysis of the Lorenz cipher. Colossus used thermionic valves to perform Boolean and count
Cryptanalysis of the Lorenz cipher
…end of the war in Europe, long after wholesale decryption had been established. 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…
The Lorenz SZ machines had 12 wheels, each with a different number of cams (or "pins"). Wheel number 123456789101112 BP wheel name ψ1 ψ2 ψ3 ψ4 ψ5 μ37 μ61 χ1 χ2 χ3 χ4 χ5 Number of cams (pins) 434751535937614131292623