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BEDSTEAD :
(in Tunny). That part of a Robinson which reads the tapes by
photo-electric means, and conbines and compares the results as
required.
BEETLE :
1. The adjacent letters on a rod of an Enigma wheel, especially a
clear bigram or any of its twenty-five possible encipherments
when no turn-over intervenes.
2. Two occurrences of a letter on (each of) the rods of an Enigma
wheel, corresponding to two circults in the wheel which have the
same interval between their right-hand terminals as between their
left-hand terminals measured in the same direction.
3. Two constatations involving the passage of current through the
same loop in the unmoved wheels and in the same direction;
cf. Starfish.
BEGINNER :
A crib or possible crib for the beginning of an enciphered message.
BERLINISMUS :
Practice, observed in a series of Enigma messages originating from
Berlin, of assigning successive outside indicators such that each
letter of any one of them was two places further down the alphabet
than the corresponding letter in the previous outside indicator
(e.g. CRM, ETO, GVQ, etc.), thereby suggesting that they had as
message settings the letters next to each (i.e. in the above example,
the letters DSN, FUP, HWR, etc.); as in fact proved to be the case.
BIFID :
(of a cipher system or cipher). Characterized by a dividing of
each letter of the plain text into two elements (normally the co-
ordinates of that letter in a key-square of 25 letters), a systematic
rearrangement of these elements, and their substitution, in pairs,
by the letters of which they are the co-ordinates in the same, or
another, key-square,
BIGRAM :
A pair of adjacent (or otherwise associated) letters, figures, or
other units in a text whether cipher or plain; vertical bigram,
a pair of letters occurring one below the other when a text is
written out in equal lines.
BIGRAM COUNT :
A tabulated record of the frequency of occurrence of different
bigrams in one or more texts. (Also called bigram frequency
count)
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