Page 129 - The Secret War in the Italian front in WWI (1915-1918)

CHAPTER SIX

oPeraTIonal securITy
In addition to a constant accuracy in encoding operations, frequent changes of keys and ciphers would
be assured, because the collection of a considerable number of uniformly encoded cryptograms
in the hands of enemy analysts facilitates the solving process enormously. Indeed, the abundant
homogeneous cryptographic material makes statistical analysis more reliable and increases, for
instance, the likelihood of repeated code groups being detected. As already mentioned, this can
mark the start of a code or chipher breaking.
The enemy’s skill in cryptolology must be never underestimated !
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It is intuitively clear that a short dispatch protected by a cipher and a key that are rarely used is
much safer than a long telegram or more telegrams encoded in the same manner. Claude Shannon
theoretically validated this concept in 1949, identifying a ‘minimum distance’, that is the maximum
length of a cryptogram or set of uniformly ciphered cryptograms below which multiple solutions
are allowed or, in other words, the text is not decryptable .
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Therefore, the more intense is the generated traffic, the shorter the operating lifetime of ciphers,
and especially of keys, must be. This avoids providing the enemy with enough cryptographic
material to break the system. Another method to achieve the same goal consists of using many
ciphers at the same time to reduce, for each of them, the number of intercepted cryptograms while
increasing the workload of enemy analysts who had to cope with many different encoding systems.
During the war, the undereducated or short-sighted operators who did not comply with coding rules,
jeopardized the security of even excellent cryptographic systems. French Colonel Marcel Giviérge
- one of the leading figures in the cryptologic war on the western front - stated that “One should code
well or not code at all”. In fact, when not coding, one risks disclosing some information to the enemy,
yet when coding inefficiently, one provides the enemy with the opportunity to break a cipher and
therefore to disclose a greater amount of information concerning oneself and his brothers in arms .
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A peculiarity of military cryptography therefore was the need to instruct in basic cryptography
methods hundreds and at times thousands of code operators and telegraphists who had to often
work in all but favourable conditions. The lack of a basic knowledge of cryptology for many
Italian operators, at the beginning of the WWI, was not a marginal cause of some of the successes
obtained by Austro-Hungarian analysts.
Another extremely crucial problem arising during the harsh radio cryptographic battle taking
place between the two opposed parties regarded the keys which, in addition to their programmed
changes, had to be immediately replaced whenever their loss was certain or even just suspected.
The frequent and sometimes unpredictable keys changes required very safe transmission channels.
In fact, according to a general principle that is still valid, the decrypting of encoded dispatches by
the enemy should be avoided, even when ciphers or codes fall into the enemy’s hands and security
relies exclusively on keys . On the other hand, keys had to be delivered - often in a short time -
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to numerous units deployed to extensive front lines, including faraway and remote locations, at
times connected via radio only. Solving the problem of the keys’ security transmission, which do

30 First principle of cryptography 1 (F.L. Bauer, Decrypted secrets, Methods and Maxims of Cryptology, Springer - Velag,
Berlin, 1997. p.205 – 207).
31 Claude Shannon, Communication Theory of Secrecy Systems, Bell System Technical Journal, 1949, Vol. 28(4), p. 656 - 715.
32 M. Givierge, Questions de Chiffre, op. cit, the statement is attributed to an important and unspecified French personality,
at the conclusion of the the article.
33 This principle was enunciated by Kerckhoffs, (Auguste Kerckhoffs, La Cryptographie Militaire. Journal Des Sciences
Militaires, Janvier 1883, 2° Desiderata) as one of the basic features of a cipher. Many of the ciphers used during the WWI
did not meet such criteria.

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