The 1944 Bletchley Park Cryptographic Dictionary

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DRUM :

(in Hagelin). That cylindrical part of the machine which carries, and is in part constituted by, the clip-bearing bars, and which is made to revolve once for the encipherment or decipherment of each letter, then imparting a varying kick to the printing wheel. (see Hagelin).

DUD :

(esp.). An Enigma message, on an already solved key, which fails to decipher (Usually owing to faulty indicators).

DUDDERY :

(in Enigma). The room to which duds are sent for further investigation.

DUENNA :

A machine specially designed for breaking Enigma keys on a crib when the wiring of the Umkehrwalze is unknown.

DUMMY :

1. A letter, figure, or other symbol, or group of such, included in a cipher or code message, usually for no other or no other known purpose than to perplex the cryptographer.

2. A cipher or code message sent merely as practice, or to produce an impression of activity where real traffic is rare or non-existent, or to complicate the work of the cryptographer.

3. A letter, figure, or other symbol used e.g. to fill blanks in a stencil cipher or transposition cage or to complete the final group, e.g. in four-figure or four-letter traffic transmitted in groups of five; a filler.

DUMMY GROUP :

A group of dummies (see dummy 1).

E BAR :

1. n. A barred E (Ebar), sent in Morse as ..-..

2. a. Characterised by having Ebar in the preamble.

E BAR v :

(in Enigma). To determine the stecker after wheel-order, ringstellung and message-setting have been found, by testing stecker assumptions on a cribbed message.

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