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.
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
The Lorenz SZ42 machine with its covers removed. Bletchley Park museum
The Lorenz SZ machines had 12 wheels each with a different number of cams (or "pins"). OKW/Chi wheel name ABCDEFGHIKLM BP wheel name ψ1 ψ2 ψ3 ψ4 ψ5 μ37 μ61 χ1 χ2 χ3 χ4 χ5 Number of cams (pins) 434751535937614131292623