The 1944 Bletchley Park Cryptographic Dictionary

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GROUP :

1. Two or more letters, figures, or other symbols forming a unit in any code or cipher.

2. (especially). A series (usually 3, 4 or 5) of letters or figures or letters and figures used for a unit of plain language in a particular code; a code-group.

5. One of the series of letters, or figures, or letters and figures (usually 5 in number) separated by pauses in which a code or cipher message is normally transmitted or set out.

A number of wireless stations associated or working together.

GRUNDSTELLUNG :

(especially). The basic setting, changing daily, employed by all users of a particular Enigma key for enciphering (or rather, enciphering twice) their message settings.

G.T.O. :

Short for German time of origin.

HAGELIN :

1. A machine cipher in which the plain language is subtracted (by letter subtraction) from a key of great length produced from (five or) six short-period components embodied in the wheel-patterns and the arrangement of clips on the bars of a revolving drum. Each wheel has a number of pegs round its circumference corresponding to its period (the periods of all the wheels being prime to each other); and the same number of letters in alphabetical order round its outer edge for setting the wheels in any indicated, position.
Each peg is set in the active or inactive position, according to the set-up in use at the time, the sequence of active and inactive positions constituting the pattern of the wheel. At a fixed point behind each wheel each active peg moves a lever which, in turn, activates as many (usually) of 27 bars on a revolving drum as have their clips set opposite it. The number of bars so activated constitutes the kick of the wheel.

Some models have one clip, some two, on each bar, capable of being set opposite any of the wheels or in a neutral (non-operative) position. When the two clips on any one bar are both placed opposite wheels they are said to overlap and the total number of activated bars (when both such wheels have active pegs in contact with their respective levers) is one less than the total kicks of the wheels concerned for each such overlap. The wheel at the left side of the machine, by which the letter to be enciphered (or deciphered) is set, is normally lettered in the opposite direction to the printing-wheel alongside it, and capable of being set in any of 26 different positions relative to the latter, giving 26 different slides and 26 corresponding, self- reciprocal, substitutions.

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