Page 203 - The Secret War in the Italian front in WWI (1915-1918)

CHAPTER NINE

showing the last efforts, on the Austrians’ part, to
avoid a war with Italy before 24 May 1915. For
each telegram of the list, two numbers, the date,
and a short summary of the contents are reported.
Many years after the war, Sacco said that in 1916 he
had asked the Minister of Foreign Affairs whether
it had intercepted and kept the telegrams between
Vienna and the Embassy in Rome, achieving
the information that many telegrams had been
intercepted and then piled up in a depot of the
central post office in Rome, piazza San Silvestro,
as they could not be decrypted.
Sacco requested that the whole lot of material
be confiscated, but despite the possession of the
cryptograms, breaking a over-encoded dictionary
with 20,000 items without any other information
regarding the code could be very hard to manage.
However, in the summer of 1915 the Austrians had
published the Rotbuch, the red book of plain text
telegrams between Burian and Macchio , in the
56
attempt to show that Austria had done everything
Picture 10 possible to avoid the war, committing a serious
cryptologic error. The list closing the Sacco
notebook is just based on the Rotbuch showing assumptions on the correspondence between the
numbering of the Rotbuch and the numbering of telegrams intercepted by the Ministry of Foreign
Affairs (picture 11). While Sacco had many encoded and plaintext telegrams yet it was not easy
to associate each ciphered to a clear telegram, also because the Austrians had not published all
telegrams between Burian and Macchio, having of course selected those that best served their
purpose.
Sacco reveals in his Manual:

We were in possession of many cryptograms and various plaintexts that we knew corresponded
to those cryptograms, although it was not possible to associate any cryptogram and its
corresponding plaintext. The cryptograms comprised groups of four letters and groups of
five letters. The latter all began by 1; therefore, the code must necessarily comprise 20,000
groups .
57

He continues explaining how he finally broke this code taking advantage of a naive Austrian
operator who suddenly decided to also encode the preamble in every telegram, which had been left
as plaintext until that moment. Those preambles were all structured in the same manner, therefore
the operator, while convinced of increasing security, was giving the cryptanalysts a tremendous

56 David Alvarez, Italian Diplomatic Cryptanalysis in World War 1, Cryptologia, 20, no.1, 1966.
57 L. Sacco, Manuale, op. cit., p. 238-240. Only in the 1947 edition of the Cryptography Manual, paragraph 157 (“The Italian
Cryptographic Unit during WWI”) Sacco confirmed that this was exactly the Austro-Hungarian diplomatic cipher: “We would
like to recall the decryption of an Austrian field cipher (N.108) as well as of the diplomatic code (N. 111)”. This paragraph,
just as the entire historical section, is not included in the English translation of the Sacco’s Manual of 1977. It is therefore
likely that Alvarez and other English-speaking researchers ignored the details of the forcing of the Austrian diplomatic code.

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