Lorenz SZ40/42
The Lorenz cipher attached to teleprinters for high-command communications ("Tunny" to the British).
It used 12 wheels: 5 chi, 5 psi, and 2 motor wheels. Each wheel had pins (active/inactive) that
generated a pseudo-random key stream XORed with the plaintext using the Vernam cipher principle.
Used for Hitler's communications with his generals. Broken by Bill Tutte's brilliant deduction of the machine's structure from intercepted traffic alone -- without ever seeing the machine. This led to the creation of Colossus.