Coding and Decoding:
A Way of Communication During WWII
Prepared by: Kim Cox
Two things made the German Military a success during WWII, and that was organization and communication. “Blitzkrieg” allowed them victory after victory in Europe. This operation employed tanks (panzers) and dive bombers (Stukas). They cut off England’s supply line at sea with a well-aimed submarine “wolf pack” assaults on fleets.
The Germans used an electro-mechanical device; Enigma to encode information which assured the adversary would not seize critical data. They believed that even if the machine was captured by their enemy, it would be useless to them. Both receiver and sender had to have the same key, describing how the message was encoded.
The Enigma machine resembles a typewriter, but with rows of lights in the middle and three thumbwheels in the back. A project called Ultra which was a focused attempt to break the enciphered messages, and was the Allies greatest secret. The Poles begun this project, then the British continued it and later was supported by the Americans.
Messages sent to their various units had different keys. Messages meant for the Navy (Kriegsmarine) were not readable by the Air Force (Luftwaffe). Communication could be directed to the appropriate unit by assigning different keys to different units.
Three reasons for using codes for message transference was to hide the meaning of the message, in case the transference medium can’t carry voice (telegraphs can only transmit dashes and dots), and to make transmissions more efficient.
Encipherment, in which letters in plain text messages are represented by letters or characters according to some scheme and coding, in which words or phrases are represented by symbols were the two methods of preparing a message for transmission. Cryptology is a two-part science of making and breaking enciphered information. Cryptography is encoding. Cryptanalysis is the breaking of codes. Superencipherment is when the message is first coded, then enciphered. This makes the code twice as hard to break.
Codes are words made into numbers and usually kept on a list or book of phrases. Such as:
1006 rendezvous
1005 location
1004 ammunition
1003 attack
1002 will
1001 coast
“Attack coast location” would be 1003 1001 1005. This type of message is extremely complex if the code groups aren’t arranged alphabetically as you can see my example was not. This system was used by both sides during WWI. To use this type of system, every group needed a code-book and if the book was captured, the enemy could decipher the messages. During WWI, in 1914, the German warship, Magdeburg grounded in the Baltic and because of errors, the Russians were able to salvage the code-book and the German’s didn’t know the codes were no longer secure; therefore, they continued to use them.
Mono-alphabetic substitution was the simplest of all ciphers. A second alphabet is randomly written out under the original alphabet.
Example:
abcdefg . . . z
LHNTBER . . .
Rotating cylinders and mechanical ciphering rings have been used since ancient civilization. A ciphering devise consisting of a number of rings on a common shaft was invented by Thomas Jefferson. Three men simultaneously invented the first electro-mechanical rotor device. Edward Hugh Hebern from the US was first in 1918 and was used by the Americans in the second world war. Hugo Alexander Kock from the Netherlands in 1919 invented his own machine and Arvid Gerhard Damm from Sweden in 1919 came up with another version.
The Poles kept their eye on Germany, their neighbor during the period between the world wars. The Enigma codes were broke by a team, comprising of Henryk Zygalski, Jerzy Rozycki and Marian Rejewski. By the end of the war thousand of people, anyone with high tech computers were decoding Axis messages. And it could have never been accomplished without the pioneering efforts of these three men.
Germany’s naval messages abruptly underwent excessive major changes in 1926 and the Poles could no longer decipher them. By 1928, Army transmissions followed their lead. They learned by espionage that the Germans had begun to machine encode their messages.
Hans Thilo-Schmidt persuaded his brother, a Lieutenant Colonel to give him a job and part of that job was to destroy invalid Enigma codes. This granted him access to information he sold to the French. He equipped Gustave Bertrand, French Intelligence with a booklet containing the Enigma machine’s setup procedures. Only two things were missing from the book and this was the rotor wiring and information on the keys.
The French and the British agreed that the information was insufficient and could not be used. Bertrand offered it to Rejewski in Poland. He was happy to receive the booklet. Then Schmidt obtained some outdated Enigma keys which Rejewski had requested from Bertrand, and they were sent back to Poland.
The Poles had the keys used to convert plain text to code, messages in code and messages in plain text. Eventually they were able to make a duplicate Enigma machine, based on a commercial copy with the rotors rewired. They set up the machine according to the codes, but their first try at encoding came up as gibberish. They rechecked their equations numerous times until Rejewski was almost ready to give up. Then he wondered if the wiring from the keyboard to the scrambler was A to B, B to B, etc. instead of like the commercial model’s Q to A, W to B, (keyboard order). After rewiring, another test was ran and they succeeded with plain text. This was 1933 and their Enigma replica was functional.
However, this was only half the battle. It was still useless without the keys. A fragment of plain text in order to correspond to a section of code of the same length is a “crib.” The Poles were furnished with cribs unknowingly by the Germans. Most of their messages started with “anx” (an means to in German and x is a word separator).
It took the Poles a year to construct a card catalog of each of the possible positions. By November 1, 1937 the card catalog was useless because the Germans changed the umkherwalze wiring and it took the Poles less than a year to finish another card catalog, which the Germans changed their method of enciphering the keys, rendering the card catalog useless again.
There were many complications in breaking the Enigma machine codes. The Germans added two new rotors; making five available on December 15, 1938, but only three were used at any one time. Knowing that their country was about to be invaded by the Germans, the Poles shared their information with the French and the British. The British tried to break the codes but the Germans had added complications, making a break impossible. The Poles gave the British their complete solution of German codes, their Enigma copy and bomby (a machine that tried different cycles of codes, made a ticking noise as they worked and stopped when they arrived at a solution) to the British on July 25, 1939.
Four days after Hitler invaded Poland; the code breakers packed up their equipment and left for France, although they had to destroy their equipment on the way. They continued their work in France and shared with the British, using their equipment.
How was the Enigma codes ever ciphered? The codes could have been unbreakable with the methods available at that time. That is if the machine had been used correctly. The Germans believed the Enigma invincible and that was their biggest mistake. Occasional operator laziness combined with procedural errors allowed the Poles, then the British to break the invincible codes. Each army unit used two Enigma operators. One worked the machine while the other wrote down the lit-up letters on the lamp board. These men weren’t always properly trained how to use the machine and picked their own message keys, often making poor choices.
However in the navy, only officers were able to set up the machines, making them more secure. Sub-codes were carefully chosen, minimizing any possibility of a code breaker deducing it. The code lists that were printed with water-soluble ink were always kept under lock and key. These precautions proved to be very effective and the Allies didn’t crack the naval codes until two years after they did the army’s.
Sources: The Enigma Exhibit—Museum of National Security http://www.nsa.gov.8080/museum/enigma.html
The Alan Turing Internet Scrapbook—Critical Cryptology: The Second World War http://users.ox.ac.uk/~wadh0249/scrp2.html
The Enigma Machine—Museum of Science and Industry http://www.msichicago.org/exhibit/u505/ENIGMA.html
How The Poles Broke The Enigma Code Prior to WWII 1926-1939 http://members.aol.com/nbrass/1enigma.htm
Code breaking and Secret Weapons in WWII http://members.aol.com/nbrass/enigma.htm
German Enigma Cipher Machine/History of Solving http://www.gl.umbc.edu/~lmazia1/Enigma/text.html
