Page 255 - The Secret War in the Italian front in WWI (1915-1918)

CHAPTER ELEVEN

After a series of bureaucratic postponements, the
distribution of the final edition of the Code D also called
Dizionario di sillabe e parole (Dictionary of syllables and
words), occurred on 10 December and deferred, for some
units, until 24 January 1918 .
74
O. Marchetti recalled that “a coding and decoding dictionary
for lower units” was adopted in June 1917 instead of the
Pocket Military Cipher. The difference between the two
dates - June and December 1917 - could be the result of
either an error by Marchetti or the adoption, in June 1917,
of a dictionary equal or analogous to the already mentioned
Small Telephone Code compiled by Luigi Sacco in 1916.
No evidence supports this assumption to date, though it
is worth to mention that Ronge assumed in his memoirs
of 1943 that Marchetti’s pieces of information and date .
75
Summarised below are the fundamental characteristics of
the D code taken from a ‘blank form’ with pencil notes
corrections and comments, probably by Sacco himself,
which he kept for years. This is the first release, which 11.13 Cover of the “D Code”, first
differed slightly from the final one. Pictures 11.13 and 11.14 edition (ISCAG Library)
show the cover and two pages of this version, respectively .
76
The D code, a two-part booklet, including a coding and a decoding section, uses three-digit code
groups and have therefore very small dimensions compared, for example, to the SI, in accordance
with its application as a trench code . The main distinctive features of the D are its ‘temporary
77
nature’ and the related random drawn of the code group for each plain term . The set of draws
78
was the ‘key to the code’ that each Division or group of units was required to modify at least once
a month, if the D code was used in radiotelegraphy. Homophones were also present as shown in
picture 11.14.
This methodology application required a larger management effort by the operating units than non-
temporary codes, and it did not enable communications outside a set of correspondents that shared
the same version. However, the ’temporary nature’ was a remarkable innovation that protected
the code from cryptanalysis, for it ‘fed’ the enemy with several versions, variable in time . In
79
fact, the work to draw lots and draft specific ciphers for each group of units was well repaid by

74 AUSSME, Series F2, env.45. In an official document accompanying the distribution of the code to some units, the date of
10 December has been cancelled by hand and replaced by 24 January.
75 O. Marchetti, op. cit., p.173, M. Ronge, Der Radiohorch, op cit., p. 52a.
76 Library of the ISCAG, Coll. XXXI A, no. 11129. The codes and ciphers contained therein were delivered by Luigi Sacco
to the ISCAG library in the year 1947.
77 The encoding section comprises 1.000 entries, the first 800 of which include punctuation, numbers from 0 to 9 (part one)
and, in alphabetical order, letters, syllables, words, and phrases (part two). Another 200 items (part three) remained available
for Headquarters for names of units, places, officers, etc.
78 The three dots next to the plaintext entries indicate the three digits of the number to be drawn by lot.
79 Gylden himself, while being critical of Italian cryptology, did not hide the problems mentioned above and at the same time
acknowledged the validity of the choices made by the Cryptographic Unit. Thanks to those choices, “the classification of
codes was much more difficult and considerably increased the statistical work” of cryptanalysts (Y. Gylden, op. cit., p.80).
This piece of information, like some others reported by Gylden on Italian ciphers, does not appear in Ronge’s book and is
therefore unclear how Gylden became aware of it.

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