page_title: General der Nachrichtenaufklärung
section_title: Technical description
hierarchical_section_title: General der Nachrichtenaufklärung / Soviet cryptanalysis / Cryptanalytic effort against Soviet Union / 3-Digit codes / Technical description
caption_attribution_description: English: Figure VI of TICOM document I-19d Report on Interrogation of KONA 1 at Revin, France, June 1945. Image is of 3-Figure semi-alphabetic code book Other information Image is printed on orange blotting paper.Dianna has already agreed TICOM files before 1956 are in public domain. This is from 1945, is military in nature.
context_page_description: The GdNA was the signals intelligence agency of the Heer, before and during World War II. It was the successor to the former cipher bureau known as Inspectorate 7/VI in operation between 1940 and 1942, when it was further reorganised into the Headquarters for Signal Intelligence between 1942 and 1944, until it was finally reorganised in October 1944 into the GdNA. The agency was also known at the OKH/Gend Na, GendNa or Inspectorate 7 or more commonly OKH/GdNA. Inspectorate 7/VI was also known as In 7 or In/7 or In 7/VI and also OKH/Chi.
context_section_description: The first 3-digit ciphers were very simple in form, consisting of several pages, ten at most, and contained alphabetically semi-hatted or completely hatted, the numbers 1 to 0 and punctuation marks. See Fig IV.
  Soon afterwards the letters of the alphabet were put in their alphabetic position in the book. See Fig V.
  Besides the above types of codes, syllabic codes contained few words but practically all the possible syllables which could be formed out of 2 or 3 letters. All codes of this kind which were broken were alphabetic. See Fig. VII
  After some months, the strictly alphabetic nature of the books was given up and the alphabeticity only maintained within the area of a letter. The numbers were at the same time distributed at random over the page. See Fig VI.  The book could have 1000 groups, but Oberleutnant Schubert stated that the average number of groups was 300–800, stating:  in general small scope, but frequent change. If the codes were smaller than 1000 groups, alternatives were given either to pages or first figures of the lines. The substitutions could be constructed without any recognizable system or they could be made up from a Latin square, with the square usually lasting about one month, although with the Air Force, it sometimes lasted longer. Schubert stated that towards the end of the war, there appeared quite isolated 4 to 7-digit substitution, presumably private systems of the respective cypher departments, but appeared very seldom.
  From the beginning of 1943, most 3-digit codes no longer contained single letters but used the initial letter of the words for this purpose. In order to indicate which meaning was to be used two groups were introduced:
  736 1) Read the initial letter
  737 2) Read the whole word
   
  The 3-digit groups were read in the order of page-line. The recipher of 3-digit ciphers was as varied as in the case of 2-figure ciphers.  Each figure was re-enciphered separately. This is to say, for the page numbers, a hatted order of the figures 1 to 0 was substituted. Thus Page 1 became 4, 2 became 6 and so on. Fig. VIII.
  3-digit code R3ZC which was mentioned by Corporal A. Faure of NAA 11 and was discovered as part of the Norway codes. It was a code with 10 pages of 100 positions each, 10 x 10 alphabetically arranged. One column of each page, the 8th was empty. Only the 100's and 10's figures of each group were reciphered.
  The 3-figure code, it is clear from all interrogations, was mainly used by the Army, but also by the Air Forces. According to a report by  Uffz. Karrenberg of Group VI, on regimental networks and for less important messages on the level of assault armies, mainly the 3-digit codes (with a 2-digit Latin square encipherment) was used. KONA 1 personnel stated that every Army Group down to Battalion had its own 3-digit code.
  It is curious to note that a good deal of plaintext was inserted into the 3-digit enciphered code as it was transmitted. Gerlich pointed out the advantages of plaintext insertion stating: They often gave words and names not contained in the code. 3-figure traffic was always solved when one encipherment was available 3-figure traffic was only slightly more secure that 2-digit code traffic and was 80% readable. It was known that Air Force codes were often current for much longer periods than those for the Army, and thus be able to find depth. Army 3-digit codes were changed after a big operation and were in use for one week to one month. However, all 3-digit codes were readable and Lt. Col. Mettig stated that from spring 1943 to 1945, 2-digit and 3-digit traffic was read regularly, providing a large amount of tactical intelligence.
  The operational 3-digit codes were discontinued in 1943 and replaced by 3-digit Signal Codes, which were different only in that they contained no letters, only words and phrases of importance, and were not alphabetic but had meanings grouped under headings such as attack, defend, enemy movements. Each meaning had two or three, 3-figure groups allotted to it. As in the case of the former code, anything not in the codebook was sent in pla
caption: Fig VI. Example of 3-figure semi-alphabetic code book
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