The Bletchley Park 1944 Cryptographic Dictionary formatted by Tony ...

The Bletchley Park 1944 Cryptographic Dictionary formatted by Tony Sale (c) 2001
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ADDER :
A series of figures or letters (or a group or single unit of such
a series) which is added figure by figure or letter by letter, usually
non-carrying, especially to the figures or letters of code-groups in
the process of reciphering, and subtracted from cipher groups in the
process of stripping a reciphered code message; a reciphering key or
subtractor.
ADDER NUMBER :
A daily-changing number which is added to a basic number in the
process of determining the page of the call-sign book, known as the
Bird book, to be used on a particular day.
ADDER TABLE :
A reciphering table applied by addition.
ADDITION :
A process (used in enciphering, reciphering, deciphering, etc.)
whereby two figures, two letters, or a letter and a figure are
combined and the result denoted by a figure, a letter, and a
letter respectively, on a conventional basis.
1. Addition of figures is usually non-carrying and in the
scale of 10, the series 0 1 2 3 4 5 6 7 8 9 being treated
as cyclic; so that 1 + 2 = 3, 5 + 9 = 4; but ordinary
"carrying" addition is occasionally used, and non-carrying
addition in other scales, e.g. 11, when 5 + 9 = 3.
2. In the addition of letters the letters A - Z may be treated
as having the values 0 - 25 and as forming a cyclic series;
addition is always non-carrying in the scale of 26, so that
A + O = O, I + O = W, M + S = E. Or A - Z may be treated
as having the values 1 - 26, i.e. 1 - 0, so that A + O = P
I + O = X, M + S = F.
3. Addition of a letter and a figure is similarly non-carrying
in the scale of 26, the figure indicating the number of places
to move to the right in a cyclic alphabet, so that A + 4 = E
Y + 5 = D, cf. Gronsfeld.
ADDITIVE. a :
(used especially of recipher keys). Applied by addition.
ADDITIVE. n :
= Adder.
ADMIT :
(of an Enigma message). To produce no crashes with (a particular
version of a crib).