TENTATIVE LIST OF ENIGMA AND OTHER MACHINE USAGES 30 March 1945

Page 3

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29 March 1945 page 3

GERMAN ARMY AND AIR FORCE ENIGMA

The machine itself, except for modifications introduced dur-
ing 1944, is exactly the same as the Naval 3-wheel model. It
uses any three out of five wheels, these being the five single-
notch Naval wheels with settable rings. It has a fixed re-
flector (Unkehrwalz "B", same as Naval). The Stecker is plug-
gable, and, as on the Naval machine, necessarily reciprocal.

During 1944 a pluggable reflector ("D") was gradually intro-
duced, and is now widespread though not yet universal. Some
Air Force keys, e.g. Jaguar, have a device called Enigma Uhr
which can be attached to the Stecker board; by setting it in
any one of 40 positions, 40 (mostly non-reciprocal) Steckers
can be produced from the one plugged up for the day.

Whee1-order and Ringstellung usually changes daily (rather
than two-daily), as well as Stecker. On some keys, the daily
wheel-order is changed cyclically after eight-hour periods.
The pluggable reflector is usually changed about every ten
days.

There are more keys than in the Navy - about 50 Air and 40
Army keys have been identified. Up to the Fall of 1943, these
were distinguishable by external discriminants. Double en-
cipherment is used only as an emergency measure.

A six-letter indicator is used. If, for example, XVE JLG is
received, the operator sets his machine at XVE and deciphers
JLG, the result being the message setting. "Cillis" are pro-
duced by the tendency on the part of the encipherer (1) to
take the final setting of one message as the "Grund" (XVE in
the example) of the next, and (2) to choose "keyboards" (like
PYX, ASD, etc. - adjacent keyboard letters) for message set-
tings.

If the reflector is known, the usual attack is by 3-wheel
bombe, using a medium length crib or a menu derived from
Cillis. If the reflector is unknown, it may be recovered by
means of a long crib (4 to 8 lines of 26 letters) by (1) hand
"5tecker-knock-out" method, (2) Duenna, (3) Autoscritcher, or
(4) Giant. If the Uhr is used, these "D-methods" are unaffect-
ed, since they do not assume Stecker reciprocity. But for a
bombe run with known reflector, the diagonal board must be dis-
pensed with.

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This page was originally created by the late Tony Sale, the original curator of the Bletchley Park Museum, and Secretary of the Bletchley Park Heritage Society. Maintenance/upkeep of this page is sponsored by ClaimControl Incident Management Software