Railway Enigma Comic Strips, Rod and Alphabet Squares
This is a demonstration of the Railway Enigma, as described in
Turing's Treatise on Enigma.
The Rod Square was an important tool in breaking Enigma. It shows
for one wheel
the encipherment of the alphabet down the right hand side for each
of the wheel start positions along the top of the square.
Click on "Rod Squares" for Railway to show the squares for the left hand wheel
number in the "Wheels" text box.
Rod pairs were an important way of breaking the unsteckered Enigma. The
"Rod Pairs" part of the procedure demonstrates the breaking of the
right hand wheel and its setting.
Rod Pairs allow comparison between the rods and a cipher text and its guessed Crib.
If the right pair have been selected, the rods reveal some
same letter pairs, at the same positions, as in the cipher/crib. When
this happens more than once it was known as a "Click" and the seperation
between Clicks, known as the "Click Distance".
The rods have to be brought into a poition corresponding to the original
Enigma encipherment of the cipher text and this is achieved by the
letter following the rod pair letters. This in effect rotates the rod letters by the numeric value
of the start letter (A=0).
The default text settings show the correct position, E, of the start
and the correct rod pairs. The multiple Clicks confirm this start and wheel number.
The Alphabet Square is also shown for Railway Enigma. It was important in finding wheel start positions
when cribs were available for messages set in depth.
Click on "Alphabet Square" to show it.
The wheels selected
refer to the rightmost wheel selected and assume that any wheels to the
left of this wheel do not increment, ie there is no carry.
If just L is selected for the leftmost wheel, then it is as if the
middle and right hand wheels were not present. This therefore gives just the
encipherement by the left hand wheel and the Umkerwalze for all possible start
positions of the left hand wheel.
If LMR is selected then all wheels are included but again, only the right hand
wheel increments as per the letters along the top of the square. The
start positions of the middle and right hand wheels can be changed by altering
the wheel starts text box. Thus rod squares can be produced for various
combinations of wheels and starts except for the wheel being incremented.
The contents of the wheel starts box are ignored
for the wheel being incremented and any wheel to its right.
The rod or alphabet squares can be printed but make sure that the square has focus by
clicking on it just before printing.
The comic strips are also produced below the rod squares. These strips
are for the same wheel, rings and start positions as the rod square.
Any entry in the steckers box and the rings box, is ignored in producing the rod Square
but will be included in the comic strips.
The comic strips presentation is the same as in the Army Enigma comic strip decoding
procedure except that because the entry order (the diagonal) is QWERTZUIO..
this is used on all vertical strips excent the Ringstellungs
A background sheet of paper has printed on it vertical strips of
letters. On the left hand side is the
representation of the Umkehrwalze (reflector), U.K.W. Since, on the Railway enigma,
this can also be turned and its Ringstellung set iit is handled just like
the other wheels.
The wheel strips contain a lower case alphabet on the right hand side,
an upper case alphabet down the centre and the
wheel wiring in lower case in the left hand column. The letter entered into
this column is the letter to which it is connected on the right
The upper case alphabet down the centre represents the Ringstellung or
tyre setting on the wheel. It is placed so that the Ringstellung
letter on this strip is alongside the letter l,(this corresponds to "Z"
on the Army Enigma) in the left hand
column of the wheel.
For Railway Enigma the default settings are the same as in Turing's
"Treatise on Enigma".