The 1944 Bletchley Park Cryptographic Dictionary

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STRIP, v :

1. To remove the true or provisional key (from a depth of reciphered code), especially by identifying good groups from good differences; also, to reduce a reciphered code message to true or provisional code-groups, the true or provisional key and the starting-point of the message on it having been previously determined.

2. To remove (the true or provisional key) from a depth of reciphered code messages, from a column of such a depth, or from a single message as above.

STUMER :

A corrupt or incorrect letter, figure or other unit in a cipher or code message.

STURGEON :

1. A German electric teleprinter letter-subtracting and impulse- permuting machine having ten wheels whose periods are prime to each other and whose patterns (representable either by series of crosses and dots or by ones and noughts for arithmetical addition and subtraction, non-carrying, in the scale of 2, cf. Tunny) are utilized in any desired order and either singly or in combination (e.g. of fours and sixes) first to alter, by addition or subtraction, the impulses of the plain Language letter as in Tunny and then to permute the resulting five impulses by causing or not causing an interchange in each of five pairs of adjacent impulses in turn, according to whether the impulse controlling that part of the permuting mechanism is a dot or a cross. Combinations of wheel-patterns to form the subtracting and permuting series are effected, e.g. in the model known as T.52C, by a mechanism called the Pentagon (q.v.) The latest model, T.52D, has no Pentagon, single wheel patterns being used instead of combinations, the regular motion of all ten wheels has been replaced by intermittent motion, the movement or non-movement of any particular wheel between the encipherment of two consecutive letters being determined by the patterns of the other wheels one- third of a revolution distant from their active (enciphering) positions, and a KTF has been introduced whose nature is as yet unascertained. As in Tunny the plain language is enciphered by one machine, transmitted in cipher, received, deciphered, and printed in clear on a tape by the receiving machine, the wheels of both machines being set in the same initial positions and the same steckers and combinations (if any) being applied in both. Thus as in Tunny, the cipher version of the message has normally only a momentary existence as electrical impulses, except when otherwise intercepted.

2. Any traffic enciphered on a machine of the above type.

STUTTERING DUMMY :

A dummy which is a repetition of the preceding letter or other symbol.

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