WWII German Cipher Machines: Enigma & Lorenz SZ


Germany entered the second World War with experience in the use of the ENIGMA cipher machine for secret military communications. The basis of ENIGMA cipher machines was a glorified character substitution involving two static encoders, the Plugboard and the Reflector, and three or four dynamic encoders, the rotors mounted within the wheels of the machine. The entry rotor stepped every character, and after a predetermined number of characters the next wheel would step on. The other wheels movement, again, determined by the previous wheel's movement. ENIGMA encrypted messages were transmitted as (ordinary) morse code character sequences between radio operators, and converted back to plain text with the use of a second machine, upon reception of the message. The machines needed to be set-up exactly the same, otherwise the received message would be nonsense! The bottom line is that the whole process was labour intensive and quite time-consuming. Mid-WWII the German High Command adopted the near-instant communication of messages provided by the LORENZ SZ teletypewriter. These machines encoded the plain text message and automatically converted it to an encrypted binary form based on the 32-symbol, 5-bit Baudot Code. The encoding process was the result of twelve moving wheels, ten of which generated a pair of obscuring characters that were successively Half-Added (binary Exclusive-OR, XOR) to the input character, in the style of the Vernam cipher. As with ENIGMA, radio was the means of communication between cipher machines. However instead of Morse Code a system of two tones representing ones and noughts was employed. The plain text of the message would be automatically typed on the receiving machine, character by character, providing the machines initial settings were identical.

For the war-time British code-beakers, it was extremely difficult to decrypt ENIGMA messages, but they were, relatively, much easier to decrypt than LORENZ messages, which were near impossible without assistance. And of course, in war-time, the German messages needed to be decrypted in the shortest possible time for the information they contained to be of significant military value.

Captain Jerry Roberts, one of the Bletchley Park's shift-leaders in the group known as The Testery, involved in decoding the LORENZ (FISH) traffic codenamed TUNNY summarised the military value of Bletchley Park's codebreakers' work as:-

    ENIGMA decrypts helped Britain not to lose the War in 1941.
    TUNNY decrypts helped shorten the European War by at least 2 years.

An ENIGMA Machine Emulator - Open / Close
Visual explanation of ENIGMA Rotor Encoding - Open / Close


A LORENZ SZ Machine Emulator - Open / Close
Visual explanation of LORENZ SZ Encoding - Open / Close