The 1944 Bletchley Park Cryptographic Dictionary

- 43 -

(continued)

In operating the machine the requisite patterns are set on the wheels, the appropriate disposition of clips is made on the bars, the wheels are set at the positions corresponding to the indicator, the slide to be used is set between the outer left-hand wheel and the printing-wheel; the first letter to be enciphered (or deciphered) is set on the outer wheel (thereby subtracting it from the slide) and the drum is rotated e.g. by a handle on the right-side of the machine. Each of the activated bars on the drum (their number on each occasion being determined, as stated above, by the total number of clips opposite wheels which have an active peg for that position, less one for each overlap) advances the printing-wheel one letter, and the final letter reached is printed on the tape, the wheels all moving on one position as soon as one letter is thus enciphered, (if the slide is S, the kick of the bars K, the plain letter P, and the cipher letter C, the above operation can be expressed by the equation S - P + K = C; and as this can be re-arranged as S -C + K = P, it is clear that the operations for enciphering and deciphering are the same).

2. (any traffic). Enciphered on the above machine.

HAT, n :

1. (in Transposition). More or less hat-shaped figure into which the text of a message in simple transposition is written by the cryptographer when the key-length is known (or guessed) and the cage is not a complete rectangle.




2. Rearrangement of a series of letters or figures or groups of these in a new and other than alphabetic or numerical order.

HAT, v :

To rearrange in any non-alphabetical or non-numerical order.

HAT BOOK :

A code-book characterized by the fact that when the plain-language terms are arranged in alphabetical order the code groups are not in numerical (or alphabetical) order; a two-part code.

HATTED :

Arranged in other than numerical (or alphabetical) order.

HAT-DIAGRAM, HAT-FIGURE :

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