The operator is provided with am emergency method of obtaining
stecker board patching to be used if the key sheet should be
compromised. A word is furnished in advance. Let us assume the word
is Christensen. He is instructed to write the first line of a square,
using the alternate letters beginning with the first without
repeating letters. He then builds the rest or the square row by row
from the remaining letters or the alphabet.
Beginning with the top letter of the last column he then
writes the letters in two horizontal rows. The stecker board couplets
then read vertically as N/I, G/O &.
SECURITY OF THE ENIGMA MACHINE.
The enigma machine is capable or a tremendous number of
combinations. The selection of 3 wheels in a certain order introduces
5 x 4 x 3 combinations. The setting of the ringstellungs introduces
26 x 26 x 26 equals 17,576 combinations.
There are 26x25x24x23x22x21x19x17x15x13x11x9x7x5x3x1
combinations for patching the stecker board. This works out to
167,613,600x62,895 x 10,395/720 equals 152,418,964,472,775
combinations. Thus the total possible combinations introduced by all
elements of the machine combined is 150 million,million,miliion.
FIRST STEPS IN "BREAKING" ENIGMA MACHINE MESSAGES - PREPARATION OF
CRIB. Messages are intercepted in the following form:
The first six letter group (OMPQTZ) contains the indicators.
This group is divided into two three letter groups thus (OMP QTZ) by
either the receiving operator or the cryptanalyist. The first three
letter group (OMP) is the external indicator and is used to set the
wheels for decoding the second group (QTZ) or internal indicator to
obtain the starting position.
In order to break the message we must try various assumed texts
(cribs) derived from experience with the habits of the German
operators and the type of traffic handled over the intercepted
messages. It is known from call signs and direction finding what
organizations (ground forces, air forces or navy) originate the
messages and from what locality.
The German operator to encode his message is given the
steckers, wheel order and ringatellung for the day, but not the
starting position. He must pick six letters for this purpose, three
for the starting position and three for a setting in which to encode
the starting position. The selection of these letters is where
carelessness creeps in to assist us in the "breaking". The operator
is apt to pick easy stereotyped combinations, such as the first three
letters on the top and middle rows of the enigma machine keyboard
(QWE AST), and use them repeatedly. One operator with a girl friend
back in Germany by the name of Cillie continuously used the six
letters of her name. The term "Cillies" has come to be applied to all
sorts of stereotyped phraseology, of which the following are examples:
"Quiet night" - - used by operator in North Africa.
"Wine barrels on hand" - -. used by operator in Czechoslovakia.
"RAF plane over airport" - - used by obliging operator in France.
"Good morning" - - used by operator in Norway.