TheCodeBreakers
It was during the Spanish Civil War, in which Russia actively aided
the Loyalists, that a cryptographic element that had served the
revolutionary predecessors of Lenin & Co. reappeared in a form both
streamlined and more secure. This was the straddling checkerboard. Its
straddling feature makes use of cipher equivalents of two different
lengths—lengths usually of one digit and two digits; the two sets of
equivalents are so constructed that the cryptographer can
unambiguously separate them when they are run together. The
cryptanalyst, however, not knowing which digits are singletons and
which form,pairs, may divide the ciphertext incorrectly, thereby
"straddling" many of the true pairs and combining two singletons into a
false
pair. The device also reduces the length of the numerical text as
compared with checkerboards in which all letters are replaced by
numerical pairs. Straddling was first employed by the Argentis in some of
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