Click for homepage
Security by obscurity

A codebook is a very old and effective method for concealing the contents of a message. Initially, codebooks were not intended for the encryption of messages, but as a simple means to make their distribution more efficient and cost-effective when sending them over telegraph lines or via radio by means of morse code. In most cases, frequently used expressions — and also words and single letters — were replaced by three, four or five-letter codes, making it easier (and cheaper) to send a message over a long distance. The international Q-Codes are a good example of this.

During WWII, codebooks were often used to encrypt a message, sometimes in addition to other cryptographic methods, such as Enigma or hand ciphers. Cracking a codebook is a difficult but not impossible task for a codebreaker. Once a codebook is captured or reconstructed, messages are no longer secret. For this reason, codebooks are often said to provide Security by obscurity.

Codebooks on this website
Österreichisches Geschäften-Lexikon (Austrian business lexicon) (1793, 1816)
Code International Lugagne (1914)
Radiokom I and II (1917)
The Peterson International Code, 3rd edition (1929)
Internationales Signalbuch 1931
S.P. 02201 - Signalling instructions of the British Admiralty (1935)
The New Boe Code (1937) - Commercial Traffic and Shipping Codes
International Q-codes
Funkverkehrsheft für die Küstenverteidigung (1943)
German Navy bigram tables used during WWII for Enigma traffic
Wetterkurzschlüssel (Short Weather Cipher) used for Enigma traffic
Reservehandverfahren (manual backup procedure)
Note that some books do not directly contain codes, but instead offer instructions on how to handle, encode and decode (specific parts of) a message. Such books are procedural rather than operational, but are nevertheless codebooks in the sens of this section of the website. A good example are the S.P. 02201 Signalling Instructions listed above, that were used throughout WWII.

Key material
When using mechanical cipher machines, such as the German Enigma, it was common practice to supply the daily settings of the machine, such as the order of the wheels and the initial position, on a so-called key sheet or key list. In most cases, a key sheet contained the settings for several days — sometimes even a full month — in advance. Please note that a key sheet is not a code­book. Nevertheless it is often treated as such, as they both contain classified cipher material.

  1. Signalschlüssel für den Funksignaldienst
    Oberkommando der Kriegsmarine, October 1939.

  2. Geheime Marinefunknamenliste (GFL)
    Oberkommando der Kriegsmarine, October 1943.

  3. GFL U.Boote (Geheime Funknamenliste)
    Oberkommando der Kriegsmarine, August 1944.
Further information

Any links shown in red are currently unavailable. If you like the information on this website, why not make a donation?
© Crypto Museum. Created: Friday 04 September 2015. Last changed: Monday, 12 February 2024 - 14:35 CET.
Click for homepage