ll-15-17 Machines (Coast Guard). At least three types of the
ll-l5-l7 machines have been used. These machines in addition
to the three multiple-notch wheels have a reflector which is
mechanically stepped, a fixed QWERTZU input sequence and cyclo-
metric rather than enigma stepping. For these multiple notch
machines, as many as 61 (out of the theoretical maximum of 64)
grenade runs may be necessary to exhaust all of the possible
stepping sequences for a four letter crib. Modified techniques
on hypo (using hypo as a grenade) have been used on this type
problem, and another procedure makes the required number (from
37 to 61) of grenade runs on a four letter crib. At times,
knowledge of the ring positions which determines the stepping
sequence is available - but little or no use of this can be
made on the bombes. In the opinion of the writer, present
high speed equipment represents a makeshift rather than an
ideal approach to this problem. A click machine, a new type
of grenade, and a new type of bombe with greatly increased
turn-over possibilities have been proposed to aid in the at-
tack on this problem. A pluggable stecker sequence would
greatly complicate this problem.
New K.D. Machine (Coast Guard). About January 1945 a new En-
igma machine with three (chosen from a set of six) nine-notch
wheels appeared. The machine has the fixed QWERTZU input se-
quence, enigma stepping and a pluggable (Dora) reflector.
Attacks on Duenna are possible but the nine-notch pattern will
complicate the problem. A pluggable stecker sequence would
greatly complicate this problem.
T Machine. In the summer of 1944 a number of the so-called T
machines were captured in a warehouse in Normandy. These
machines had been built for the Japanese, and used three (from
a set of eight) five-notch wheels, a movable reflector, a
fixed non-reciprocal input sequence and enigma stepping. No
positively identified traffic has appeared in this system -
although early in 1945 exhaustive runs were made on two cribs
placed at the beginning of two messages suspected of having
been enciphered on the T machine. For four letter cribs, 8
(out of a theoretical maximum of 64) grenade runs must be made
to cover all the types of stepping sequences. If the T mach-
ines were equipped with a variable stecker, an extremely large