Cillis

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Cillis (also: Cillies ), not authentically known as "sillies" (German: "Dummchen"), is the English nickname for the incorrect choice of the basic position and the motto key when using the rotor used in communications by the German military during World War II . Enigma key machine .

Statutory headline

The operator of the Enigma had to select an individual basic setting as “randomly” as possible for the encryption of a radio message and set the key machine accordingly. The basic position indicates the letters that are set in the three windows of the key machine from left to right, and thus represents the initial position of the reel, which is then used to encrypt the slogan key . Like the three letters of the basic position, the cipher should also select the three letters of the slogan key as randomly as possible from the 26 capital letters of the Latin alphabet , so a total of six letters between A and Z are “thought up”.

In accordance with the regulations, the operator has opted for a roller position “RDK” that is not easy to guess

In accordance with regulations, he selects, for example, "RDK" and sets the three rollers so that exactly these three letters are visible in the display windows. Now he thinks up a secret key, also made up of three randomly chosen letters, for example "ZVP". He encrypts this with his Enigma and watches how the lamps, for example "UGN", light up one after the other. He openly communicates the message key encrypted in this way to the recipient together with the randomly selected basic position in the message header of the radio message. In this case it would be "RDK UGN". The encryptor can easily use this information to obtain the true message key, which he needs to decrypt the encrypted radio message.

The Enigma of the recipient is set identical to that of the sender according to the day key . To decipher the spell, he still lacks the secret spell key, i.e. the correct starting position of the reels. He receives this information from the message head, here "RDK UGN", which he interprets as follows: Set the rollers to the basic position "RDK" and then press "UGN". Now he can observe how the "ZVP" lamps light up on his Enigma one after the other. This is the key to be set.

According to the (at that time) secret “key instructions for the Enigma key machine”, it was expressly “forbidden to use the same letters (AAA), words (is), abbreviations (Rgt.), Callsigns for your own traffic area, traffic signs (QRM ), Letters in the keyboard order of the key machine (ERT) or in alphabetical order (forwards or backwards: ABC - CBA). "

Faulty saying head

Nevertheless, this mistake was made for whatever reason. The special circumstances caused by the war may have played a role, such as extreme time constraints or stress, but comfort, carelessness or negligence can also be the cause. It is crucial that these mistakes were made by the Enigma operators and were recognized by their British counterparts, the cryptanalysts in Bletchley Park , England , and were used to decipher the German radio messages, as they could easily guess the secret key.

In particular, letters directly next to one another on the keyboard of the machine, which looks like this: 

 Q  W  E  R  T  Z  U  I  O 
 A  S  D  F  G  H  J  K 
 P  Y  X  C  V  B  N  M  L

A typical example of an incorrect choice is "QWE" for the basic position and then "RTZ" for the spell key. In this case, after encrypting the key, the result is, for example, "EWG" and thus the header, which was openly transmitted, "QWE EWG". For the British code breakers, who could read the slogan directly as well as the authorized German recipient, it was easy to guess the slogan key correctly from the first three letters of the slogan using the neighboring letters on the keyboard as "RTZ".

Further examples for the incorrect choice of the basic position and the motto key are "ASD FGH" (adjacent letters on the second keyboard line), "PYX CVB" (adjacent letters on the third keyboard line), "QAY WSX" (adjacent letters on the first two "diagonals"), “EDC RFV” (letters adjacent to the second two “diagonals”) and so on. Well-known names such as the European capitals such as “BER” and “LIN” or “LON” and “DON” or “MAD” and “RID” were also very popular as defaults for the by no means random choice of the basic position and the motto. Even proper names such as “HIT” and “LER” helped the British code breakers to decipher German radio messages.

One of the first occurrences of this kind, which often appeared in the Enigma settings, was "CIL" and "LIS", derived from the first name "Cillis", a nickname of the female given name Cäcilie , the girlfriend of a German radio operator at the time. The name "Cillis" as a name for the incorrect choice of the slogan head described remained so common in Bletchley Park and thus also fulfilled the function of an alias for this German mistake.

Occasionally the term "sillies" (German: "Dummchen") appears, for example in Gordon Welchman's book The Hut Six Story . In a later addendum, Welchman regrets the use and explains that "Cillis" is the authentic name.

literature

Web links

Individual evidence

  1. ↑ a b Gordon Welchman: The Hut Six Story - Breaking the Enigma Codes . Allen Lane, London 1982; Cleobury Mortimer M&M, Baldwin Shropshire 2000, p. 220. ISBN 0-947712-34-8
  2. ↑ OKW: Key instructions for the Enigma key machine . H.Dv. G. 14, Reichsdruckerei, Berlin 1940. (Copy of the original manual with a few small typing errors.) Retrieved: March 12, 2010. PDF; 0.1 MB ( Memento of the original from September 24, 2015 in the Internet Archive ) Info: The archive link has been inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. @1@ 2Template: Webachiv / IABot / www.ilord.com
  3. ↑ Michael Smith: Enigma decrypted - The "Codebreakers" from Bletchley Park . Heyne, 2000, p. 87. ISBN 3-453-17285-X