Page 153 - The Secret War in the Italian front in WWI (1915-1918)

CHAPTER SEVEN

identified a decryption method. In 1883, Auguste Kerckoffs created another method that could be
useful only when one had many dispatches of equal lenght coded by the same key .
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Yet, by adopting keys with appropriate length and characteristics, for instance long as the dispatch
and variable from one dispatch to the next, the work of enemy analysts becomes much more
difficult, even when they had the basic table.
The instruction manual for the Pocket Military Cipher deals with the keys and suggests -
appropriately - that they would change frequently . However, no instruction is provided about
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the length of the keys, so that the short keys distributed every five days by the STM Inspectorate,
facilitated quick decryption of Italian dispatches.
Moreover, the same manual contains a serious cryptographic error as it recommends ciphering
just “very few words in a message” , in order to make encoding and decoding operations faster
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and easier. As a matter of fact, this procedure was applied during the early months of the war - and
not only to dispatches coded with the Pocket Cipher - greatly helping their decryption process.
In his memoirs, General Ronge expressed some criticism about the use of that cipher also because,
as he writes, “Italians had been aware of its weaknesses since 1901”. Therefore, he wonders why
they had not changed it . The validity of Ronge’s statement is out of question, but it could be
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fully accepted if the Austrians had not employed ciphers analogous to the Italian one, as will be
discussed further ahead.
Andreas Figl, noticed the small number of the intercepted radio dispatches coded by the Pocket
Military Cipher, limited to “communications on the front line and, in any case, rare”, consistent
with the initial limited diffusion of radio communication in the subordinate units . When between
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late 1917 and early 1918, radio communications started being widespread inside Italian Divisions,
ciphers much harder to break than the Pocket one had already replaced it.

7.6 THE CODE SUK

The ITalIan codes and cIPhers PurchasIng
Intelligence’s most obvious method to overcome, at least in part, the difficulty of breaking codes,
consisted of acquiring them via one of the many available channels.
During WWI, the most common way was the seizure, usually during or immediately after battles,
of the mostly diffused ciphers or coding-decoding tools, such as table, grilles, ciphering discs,
rulers, trench codes, etc. In case of major turmoil, the gaining also included bulkier and more
complex codes.

49 As already mentioned, the Babbage - Kasinski and the Kerckoffs methods are based upon the reduction of poly-alphabetic
systems to mono-alphabetic systems which can be solved by means of frequency analysis. The Babbage - Kasinski method
consists in determining the length of a key exploiting repetitions of coding groups and then in dividing cryptograms into
blocks whose length equals the length of the key. Since the first letters of each block are all coded with the same key letter and
the same applies to the following, it is possible to apply mono-alphabetic system decryption methods to each set made up of
the first letters, the second letters, etc. In the Kerckoffs method the same procedure applies when one has several cryptograms
with the same length that can be juxtaposed. Thus, all letters in the first column are supposed to be coded with the same key
letter, the letters in the second column are coded with the second key letter, and so on.
50 For instance, the circular letter of the Supreme Headquarters in 1916 reports the following keys for the next month of May:
Isonzo, Plezzo, Sile, Padua and Brenta (Very confidential circular letter of the Supreme Headquarters no. 8544 of 23 April
1916).
51 Istruzione sul Cifrario Militare Tascabile, op. cit., p.15.
52 M. Ronge, Der Radiohorch, op cit., p. 51.
53 Andreas Figl, op. cit., p. 85.

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