With
the success of the recent movie "The Imitation Game" most people
are familiar with the Enigma cipher machine and its critical
role in WWII.
The Germans used the cipher with great success to hide the
positions of their submarines and take a heavy toll on Allied
cargo traffic. Had the Enigma code not been cracked by the
British team (led by Alan Turing) it is possible that the war
might have gone the other direction. The facility that
headed the code cracking is located at Bletchley Park northwest
of London, about an hour away by light rail.
The photos below are what we saw.
Along
the Fleet Street path to the tube station, we passed these great
griffin terra cotta statues on an old bank building. Sub Hoc
Floresco roughly
means "under
this I flourish".
Despite
an attractive seat mate, Steve looks solemn.
Bletchley
Park was 2 tube rides and one train ride away from central
London. There was a large museum that spanned 2 buildings
and a set of outbuildings that housed smaller exhibits.
The key aspect (if you will excuse the pun) of the this class of
cipher machine is the concept of a mapping rotor. Most
machines use multiple rotors and more rotors mean a higher
complexity ("stronger") cipher. A single rotor permutes a set of
characters into another set, but in a known fixed way.
When multiple rotors are used, the input set is mapped by the
first rotor and then the output of the mapping is mapped again
by the second rotor and so on. The power of the machine
was that the position of the rotors changed after each character
as mapped greatly increasing the difficulty of breaking the
cipher. Usually, there were multiple rotors to choose
from, say 3 out of a set of 8. Each rotor's wiring
contains a different mapping. Wikipedia has a nice writeup
on Enigma and even NSA's
historian has written a paper about the German's machines.
To crack
a cipher, you must first have messages to work on, so
Bletchley's past was very much associated with radios. The
intercepted messages were in morse code over radio and civilian
ham radio operators were drafted to be "listeners" of the code
traffic. Early radios were made using vacuum tubes, called
"valves" by the Brits. These valves came in all sizes and
shapes with varying degrees of complexity. This exhibit
shows a sample of some of the diverse valves used in radios of
the era.
The
"Mansion" at BP was on the grounds when they were purchased by
the crown for wartime activities. This estate had
beautiful grounds and a small lake.
The out
buildings, built later, housed the actual work efforts.
Some of the early structures were mere shacks referred to as
"huts".
This
swan was enjoying his breakfast in the shallow waters of the
pond.
May is
early spring in England and some of the trees were sporting
glorious blooms. Others were throwing off mountains of
pollen that had us sneezing like crazy.
The
Mansion served in a number of roles at Bletchley including the
commander's HQ, canteen and mess hall. And, the building
served as the filming set for "The Imitation Game".
The
entrance to the mansion had this plaque from the American IEEE.
Alan
Turing and his team designed an electro-mechanical machine
called the "bombe" that was used to test key hypotheses in
parallel. Motors turned shafts that turned rotors.
Very complex, very intricate, very ingenious and very
successful. This was used as a prop in the movie but was
not capable of actually solving a cipher.
The
machine consisted of relay logic and lots and lots of discrete
wires.
There
was a small period vehicle display area.
It was
not clear if this nice Packard was ever actually in service at
Bletchley.
Back in
the main museum there were examples of cipher machines.
This one, called the Lorenz, was designated the SZ-42 and had 12
rotors.
The
Lorenz was part of a cryptographic teletype system used by the
German high command.
This
bombe machine, named "Phoenix" because it was re-built from raw
parts stored after the war is functional. The operation
was demonstrated and just as described in a number of the
exhibits, it was noisy.
The
rotor dials are driven by geared shafts behind the front
panel. Every 24 rotations of an upper rotor produces a
single position change on the rotor below.
This is
an electromechanical assembly and therefore is subject to
friction. Friction requires some kind of lubrication,
usually oil. The oil is delivered using a copper tube
plumbing system dripping oil on the worm gears.
The plug
panel provides the programmability of the Bombe. Wiring
changes were done when a new day's code was being cracked.
Changes were performed each day.
The
inner wiring of the bombe rotors was quite a rat's nest and
required special fixtures to assemble and test.
The
local rail infrastructure is impressive. Plenty of tracks
and plenty of above-ground wiring. Note the nest of wires
above.
Back in
the Fleet Street area, the sun was out (sorta) and allowed a
photo of the Royal Courts of Justice building.
I did not
realize until I uploaded photos that I did not get a single
photo of an actual Enigma machine, but these are available on the
web. Bletchley Park was very interesting and we could have easily
spent more time in the main museum. But, as it was, we
burned a whole day there including travel to and from the
facility.
| Previous Adventure | ||
| Trip Home Page |
Photos and Text Copyright Bill Caid 2015, all rights
reserved.
For your enjoyment only, not for commercial use.