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TRANSPOSITION, (cont'd)
rearranged letters are again written in horizontally from left to
right and taken out in columns according to a numerical key which
may be the same as that used in the first operation or a different one
and the whole enciphering process is called "double transposition".
Complications or refinements are often introduced by using irregular
cages, e.g. combs or stencils or patterns or by variations in the
routing, i.e. direction or order in which the message is written
into the cage or taken out of it.
Transposition is also employed in conjunction with substitution, as
indicated above.
TRANSPOSITION KEY :
TRANSPOSITION CIPHER, TRANSPOSITION SYSTEM :
A cipher or cipher system using transposition.
TRIFID :
(of a cipher system or cipher). Characterised by a dividing of each
letter of the plain text into three elements (normally the co-ordinates
of that letter in a key-cube of 26 (or 27), letters), a systematic
rearrangement of these elements, and their substitution, in threes,
by the letters of which they are the co-ordinates in the same, or
another, key-cube.
TRIGRAM :
A set or group of three letters, figures, letters and figures, or
other symbols.
TRIPLET :
(in Naval Enigma). Any one of three consecutive days on which wheel-
order and ringstellung are the same, stecker and grundstellung being
changed daily, on any particular key.
TRUE :
1. (of the figures or letters of subtractors, code-groups, etc.)
(Requiring no further correction to make them) the same as those
actually used by the encipherers; (opposed to provisional).
2. (of machine-cipher depths). That are completely in depth, i.e.
as distinct from near-depth.
TUNER :
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