Operation
The teleprinters of the day emitted each character as five parallel bits on five lines, typically encoded in the Baudot code or something similar. The T52 had ten pinwheels, which were stepped in a complex nonlinear way, based in later models on their positions from various delays in the past, but in such a way that they could never stall. Each of the five plaintext bits was then XORed with the XOR sum of 3 taps from the pinwheels, and then cyclically adjacent pairs of plaintext bits were swapped or not, according to XOR sums of three (different) output bits. The numbers of pins on all the wheels were coprime, and the triplets of bits that controlled each XOR or swap were selectable through a plugboard.
This produced a much more complex cipher than the Lorenz machine, and also means that the T52 is not just a pseudorandom number generator-and-XOR cipher. For example, if a cipher clerk erred and sent two different messages using exactly the same settings — a depth of two in Bletchley jargon — this could be detected statistically but was not immediately and trivially solvable as it would be with the Lorenz.
Read more about this topic: Siemens And Halske T52
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