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Rotor Enigma Tree I → Z → A28 → K → ← C
The machine has several improvements over the Enigma C.
The top lid was made more accessible by adding
a hinge at the rear and two retaining bolts at the front.
This made it easier to access the rotors and alter the internal settings.
There are four settable rotors
that protrude the machine's top lid,
which is why this machine is sometimes erroneously called a
4-rotor Enigma. In reality there are three driven cipher rotors
(i.e. the rightmost three).
They are mounted on a removable spindle, so that their order can be
changed as part of the daily key settings.
The leftmost rotor is the Umkehrwalze (UKW, reflector).
It can be set to any of 26 positions, but is not driven by the
cipher rotors. This is different from earlier machines, in which the
UKW could be set to two or four positions, or could not be set
at all. Enigma D is also the first Enigma machine on which
the keyboard and the lamp panel are arranged in typewriter
order (QWERTZ...) rather than the alphabet (ABC...).
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It seems likely that in 1926, the Enigma D was the core design on
which all future designs
would be (partly) based. The Enigma D itself
was short-lived and was succeeded a year later – in 1927 – by the
Enigma K (A27). Military Enigma I and Zählwerk Enigma A28
are both based on Enigma D.
The machine shown above has serial number A319 and was
(re)discovered in 2024
at an auction in Florida (USA). It is currently unknown who the
original user was. It is known however that its twin brother — serial
number A320 — was bought in 1926 or 1927 by the UK
's codebreaking establishment,
the Government Code & Cipher School (GC&CS, now: GCHQ).
It was subsequently scrutinised in 1927 by cryptanalyst
Hugh Foss, who wrote
a detailed report
and developed a method for breaking it [6].
Ten years later, in 1937 — during the Spanish Civil War (1936-1939) — it helped
codebreakers William Bodsworth and Dillwyn (Dilly) Knox
to break the Enigma traffic between the Spanish Navy of General Franco,
and the Italian Navy of dictator Mussolini [7].
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The images below provide a quick overview of the features of Enigma D.
The image on the left shows the machine after opening the lid of the wooden
case. The device has three cipher rotors and a
settable reflector (Umkehrwalze, UKW).
To the right of the rotors is the
power selector.
It offers a choice
between HELL (bright) DKL (dunkel, dark), AUS (off) and SAMMLER (accumulator). 1
In the latter case, an external 4V power source should be applied to the two black
terminals at the right edge. 10 spare light bulbs
are stowed in a bracket inside
the upper edge of the case lid.
The image on the right shows the same machine with open lid. This exposes the
cipher rotors, the ETW (entry disc), the UKW (reflector), the battery
compartment and the light bulbs. It should be noted that the power knob and the
external power terminals are on the machine body
and protrude three cut-outs in the lid
when it's closed. This is different from later machines, such as
the Enigma I and Enigma K, were the power selector knob
and the terminals are fitted to the lid.
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Literally translated, the German word 'Sammler' means 'accumulator'
or 'rechargeable battery'. What is probably meant here is that it can be used
with the external battery of, say, a vehicle.
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Differences with Enigma C
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Compared to its predecessor — Enigma C — the following differences can be
observed:
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Immediately after the introduction of the Enigma D, several developments
of improved machines were started. This led to a range of commercial and military
machines, the first of which was introduced
in 1927. The following machines are more or less based on the design of Enigma D.
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- Reichswehr D (Ch.11a)
Machine with a single-ended Steckerbrett.
This eventually led to the developement of the Enigma I (Ch.11f),
which was used by the Reichswehr
(later: Wehrmacht) throughout WWII.
As far as we know there are no surviving examples of the Reichswehr Enigma D,
as the existing machines were all recalled and upgraded to Enigma I (Ch.11f).
- Enigma K (A27, Ch.11b)
From 1927 onwards, right up to 1944, this was the main commercial
(non-Stecker) machine. It replaced Enigma D and has several improvements.
This machine was also the base for the Enigma T (Tirpitz),
the Swiss Enigma K variant
and the Enigma KD.
- Zählwerk Enigma (A28, Ch.15)
This was the first of a range of Enigma machines that had a counter
and cog-wheel based rotor stepping mechanism. In addition, the rotors had multiple
turnover notches, resulting in an irregular stepping pattern.
The later Enigma G (G31, Ch.15a) is based
on the A28.
- Enigma Z (Z30, Ch.16)
This was a numbers-only version of the Enigma machine. It had just 10 keys
(0-9), 10 lamps and the rotors each had 10 contact points at either side.
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The simplified circuit diagram below, shows how the Enigma D operated.
At the right are the keys (switches), the lamps and the battery. The current
is supplied to the contacts of the right side of the first rotor, via the
entry disc (German: Eintrittswalze, or ETW). The current then passes
the three cipher rotors, each of which can be advanced by a key-press,
like the odometer of a car.
At the far left is the reflector (German: Umkehrwalze, or UKW), which returns
the current through the rotors. The current leaves the rotors via the
ETW again, and causes a lamp to be lit. Note that the process is symmetric,
or reversable, meaning that the same settings can be used for coding and
decoding. This is a property of the reflector. Unfortunately it has the
unwanted side effect that a letter can never be enciphered into itself.
This is true for all glow lamp Enigma machines.
At the bottom right is the four-position rotary selector that acts as the
power switch. It allows selection between hell (bright), dkl (dark),
aus (off) and Sammler (accumulator). When set to dkl,
a series resistor (R) reduces the current through the lamps.
When Sammler (accumulator) is selected,
the voltage from an external battery or transformer can be applied
to the terminals (P).
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Enigma D has three cipher rotors
and a settable reflector (UKW).
All four rotors protrude the top lid of the machine.
As the UKW has a thumbwheel for setting its position, it is nearly identical
to a cipher rotor. As a result, the machine is sometimes erroneously
classed as a 4-rotor Enigma, but is actually a 3-rotor Enigma with a settable
UKW. The UKW does not move during encipherment.
Each rotor has 26 positions and 26 contacts at either side, corresponding
to the letters A-Z that are engraved in the outer ring. This index-ring
can also be set to 26 positions (Ringstellung).
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The rotors are made from steel and aluminium,
and have a Bakelite inner core with
26 contact pads at one side
and 26 spring-loaded pins at the other.
Each rotor can be set to 26 positions,
each of which is identified with a letter (A-Z).
As with earlier Enigma machines, the notch ring is attached to the
body of the rotor (rather than to the letter ring).
The image on the right shows the left side of an Enigma D rotor.
The frontmost ring is called the notch ring.
It has a triangular cut-out (notch),
that is responsible for advancing
the rotor to the left of this rotor.
The notch ring has no mounting screws and is attached to the rotor body.
As a result, the Ringstellung (ring setting) serves no
cryptographic purpose, and does not contribute to the machine's key space.
This can be seen as a design flaw. It is fixed in later machines like
Enigma K and Enigma I,
in which the notch is attached to the letter ring.
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This means that with Enigma K, the Ringstellung affects
the position of the notch relative to the wiring.
The image below shows the rotors sets of Enigma D and Enigma K
side by side. If we take a closer look at the rotors,
we'll see that
the rotors of Enigma K have horizontal screws
by which the notch ring is attached to the letter ring.
These screws are missing from the Enigma D rotors.
Although the diameters of Enigma K and Enigma D rotors are identical,
they are physically incompatible. The rotors of Enigma D are 2 mm wider
than those of Enigma K. Furthermore, the spacing between the rotors is
2 mm wider on the Enigma D. As a result, the total distance between UKW and
ETW is 12 mm higher on Enigma D, which means that the rotors are not
interchangeable.
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Distance between the rotors of Enigma D.
Move the mouse over this image to see the rotors of Enigma K.
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Standard commercial wiring
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Below is the wiring of Enigma D and its rotors, as described in 1927
by Hugh Foss in his report
The Reciprocal Enigma [6].
The wiring is identical to the wiring of the later Enigma K (A27)
and can therefore be classed as 'commercial wiring'.
Note that on Enigma D rotors, the turnover notch is attached to
the rotor body, rather than the alphabet ring (index)
as on Enigma K rotors. This means that when the
ring setting is changed, the turnover of the adjacent rotor will happen at
a different letter. Furthermore, the position of the notch was identical
on all three rotors (I, II, III).
The table below shows the position of the notch when the ring is set to 'A'.
In that case, the notch is located at the position of the letter 'H', and
a turnover of the adjacent rotor will occur when the letter 'Z' in visible
in the window.
When the ring is set to 'B', the turnover will occur at 'A', etc.
Turnover = RingSetting - 1
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Rotor
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ABCDEFGHIJKLMNOPQRSTUVWXYZ
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Notch 1
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Turnover 1
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#
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ETW
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QWERTZUIOASDFGHJKPYXCVBNML
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I
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LPGSZMHAEOQKVXRFYBUTNICJDW
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H
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Z
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1
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II
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SLVGBTFXJQOHEWIRZYAMKPCNDU
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H
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Z
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1
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III
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CJGDPSHKTURAWZXFMYNQOBVLIE
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H
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Z
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1
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UKW 2
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IMETCGFRAYSQBZXWLHKDVUPOJN
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Notch and Turnover position shown when Ringstellung is at 'A'.
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This wiring is measured using the contact at the white dot as the
reference point. When the UKW is installed in the machine with its
ring setting at 'A' and the letter 'A' visible through the window in the lid,
this is the contact just in front of the contact at the top.
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With the first Enigma machines, the operating instructions were no more
than a few A4 pages created on a typewriter. With the arrival of Enigma D,
and the later Enigma K, a professionally printed instruction manual
was included, complete with photographs and a fold-out at the rear.
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Original operating instructions are extremely rare, but it is known that
the contents of the booklet were revised several times, probably to reflect
the differences between Enigma D and K.
The image on the right shows an original A5-size instruction booklet that was
probably supplied with an Enigma K. The first page of this booklet however,
shows a photograph of an earlier model, which is most likely an Enigma D.
Although it is a low-resolution photograph, it is clear that there are
no numbers printed above the upper row of lamps on the lamp panel.
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The photographs in the fold-out at the rear of this booklet,
show a different machine on which the numbers (0-9) are printed
above the upper row of letters on the lamp panel. Likewise, the
upper row of keys holds both letters and numbers. This is thought
to be a property of Enigma K.
Furthermore, the power selector is of a later construction, in
which the knob was fitted to the lid. On Enigma D, the knob is fitted to
the power selector and protrudes a cut-out in the top lid.
➤ Read the booklet
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About the booklet
The front cover holds a stamp with the number 33. The meaning of this
number is not known, but it could be the year in which it was issued (1933).
In the upper right corner,
the number A833 is written with a red pencil. This is probably
the serial number of the machine it was issued with.
As the machine with serial number A818 in the Crypto Museum Collection
has been identified as an Enigma K,
it is likely that A833 was also an Enigma K.
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Enigma D (A26) is an extremely rare machine, as it was only in production
during the course of 1926. Only a handful have survived, of which
serial numbers A319 and A320 are described below. A320 is the machine
that was acquired in 1926/27 by GC&CS (later: GCHQ) for analysis.
We will deal with that machine further down this page,
but we will first take a look at the A319.
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The machine featured above – serial number A319 –
was found in an abandoned storage locker in the US. It was auctioned in
February 2024 and is now part of the Crypto Museum collection.
Little is known about the provenance of this machine, but from the other
items in the estate it seems likely that the previous owner was a
military officer who was stationed in Germany around 1958.
The machine was found with three rotors, numbered I, II and III, all with
matching serial numbers (A319).
All rotors have paper rings with handwritten numbers 1-26, glued to
both sides. This suggests that at some point the machine may have been used
for statistical analysis or even for cryptanalysis.
Although it seems likely that this machine was manufactured at the same time
as the A320 below, there are significant – cosmetic– differences, which are
further described below.
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In 1926, Enigma manufacturer
Chiffriermaschinen Aktiengesellschaft (ChiMaAG)
had two machine offerings: (1)
Die Schreibende Enigma (the printing Enigma) — a large, heavy
and expensive non-reciprocal cipher machine —
and (2) Glühlampenchiffriermaschine (glow lamp cipher machine) Enigma D
— a portable light-weight reciprocal cipher machine that was developed
as a cheaper alternative.
As the former had been sold out completely and its successor was
not expected for another year or so, it was suggested that the British Army
might want to try the Enigma D [12].
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British Naval Attaché in Berlin Lt. Hume took up the offer and
secured an Enigma D with serial number A320.
In late 1926 or early 1927, on a visit from his friend
Commander Edward Travis – deputy head of the
British codebreaking agency GC&CS (now: GCHQ) –
Hume passed the machine to Travis, who brought to the UK
for analysis.
It is rumoured that another Enigma D (A323) prompted the British Air Force
to develop its own rotor-based cipher machine,
which became known as
RAF Enigma with Type-X attachments, commonly abbreviated
Type-X or simply Typex.
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The machine was analysed in 1927 by GC&CS cryptanalyst
Hugh Foss, who reported his findings in
The Reciprocal Enigma
[6]. In his report, Foss describes the machine and suggest a method for
breaking it, assuming that a crib (known plaintext) of sufficient length
is available. 10 years later, in 1937, Foss' analysis was used by codebreaker
Dillwyn (Dilly) Knox, to develop two methods for breaking Enigma: Rodding
and Buttoning Up. It allowed codebreakers William Bodworth and Dilly Knox
to break the Enigma K of the Spanish Navy and the Italian Navy respectively,
in 1937 [12].
On 14 September 2021, GCHQ issued a Tweet about the visit of veteran
codebraker Charlotte 'Betty' Webb to their offices at Cheltenham [7].
One of the photographs (above)
shows Betty Webb in front of a display with
two Enigma machines. Although these are a commercial Enigma K and a
Japanese Enigma T (Tirpitz), a barely readable text card in between
the two machines, provides some details about the A320 and
Hugh Foss' analysis of it: 1
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It is not clear how GC&CS heard about Enigma, the new commercial
encryption device which was being sold in Germany, but the Deputy Head
of GC&CS visited a friend of his who was Naval Attaché, and bought
one, serial number A-320. This was passed to the cryptanalyst Hugh Foss
who produced a diagnosis entitled "The Reciprocal Enigma" which
listed the conditions in which material encrypted with this Enigma
machine might be broken.
As it became clearer in the late 1920s and early 1930s that the German
military were aiming to make Enigma their main encryption device,
GC&CS cryptanalysts began to use A-320 to design attacks against
traffic encrypted on Enigma machines. At this stage no operational
traffic was available to them but that changed in 1936.
After the failure of General Franco's attempted coup in July 1936,
Hitler sent the Condor Legion, equipped with Enigma machines, to fight
for Franco in the Civil War. Two of the machines were retained at his
civil and military Headquarters, while the rest were sent in
conditions of maximum security to the principal military units.
The traffic passing between these units, and later, between them and
the German and Italian volunteers who were sent to support Franco, was
intercepted in the UK. Spanish traffic was first broken in April 1937
by cryptanalyst William Bodsworth, the first broken message being
between Franco's Navy and Mussolini's Navy.
Although much further work, and cooperation with Poland and France,
would be needed to break into German military use of Enigma, it was
the success against the network in Spain which gave the GC&CS
cryptanalysts the confidence that success was possible.
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Thanks to Anastasios Pingios for the above transcription [8].
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Differences between A319 and A320
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Despite the fact that the above two machines have consecutive serial numbers
(A319 and A320) and were probably manufactured around the same time, there
are several cosmetic differences. So far, the following differences have been
observed:
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- Position of the leather grip
On the A319 the leather carrying grip is
at the rear,
whilst on the A320 it is at the right side panel.
Looking carefully at the
wooden enclosure, the case has
pre-drilled holes at both locations.
On the A319 the
holes at the side have been stuffed.
- Window panes
The metal cover of the Enigma D, has
four oval holes
through which the current position of the three rotors and the UKW can be
observed. On the A319, these holes are covered by
shiny panes with a circular cut-out at the centre.
The cut-out is covered with transparent celluloid.
These window panes and their mounting screws, are
missing from the A320.
It is possible that they were originally present but were removed for some
reason.
- Numbers on lamp panel and keyboard
On the A319, white numbers are visible on the
top row of the lamp panel,
and also below the keys.
These numbers are missing from the A320.
It is believed that the numbers were introduced on Enigma K (A27),
and were originally not present on Enigma D.
After close examination of the A319, it has become clear
that these numbers are handpainted (rather than screen printed).
From the discolouration of the white paint,
it is obvious that the numbers were added many years ago,
probably when the machine was issued in 1926.
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Apart from the differences, there are also similarities:
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- Missing power knob
The black knob of the power selector is missing from both machines
(A319 and A320).
It is narrower than that of the later Enigma K, and
protudes a cut-out in the metal lid.
As it was probably cast in a light metal alloy, and has a 4 mm hole to
fit the axis of the power selector,
it might have been fragile, as a result of which it could have been broken.
A more likely explanation is perhaps that the knob was removed deliberately by
the original user, as it was a nuisance to place it in the
north/south position – in
between two settings – each time the lid had to be opened. This is especially
true when the machine is used for analysis, which was the case with the
A320 and probably also with the A319.
- Serial number position
The serial number is
stencilled to the front of the wooden case.
The serial number is also impressed into the bottom of the machine's
base plate (near the rear edge),
on the lamp panel mask (inside the machine), and
at the right side of the cipher rotors and the UKW.
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The Enigma D is held in the wooden case by four large bolts at the
bottom of the case.
After removing these four bolts, the machine can be lifted from
the case. Unlike the later Enigma K and Enigma I, Enigma D
does not have a metal case shell. The wooden case acts as an enclosure.
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This is particularly visible when looking inside the battery compartment
before lifting the machine from the wooden case, as shown in the image
on the right. There is no box to hold the battery, just four metal brackets
at the edges.
Also visible in the image on the right are the power selector and the external
power terminals which are permanently mounted to the machine body. They
protrude the top lid
through three cut-outs.
This is different from later machines, were they are
mounted to the lid.
Note that the knob of the power selector is missing here.
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The image at the top of this section shows the
bare machine after removing
it from the wooden case. At the bottom is a
large steel plate
that acts as the machine's base. Just above the base plate is a horizontal
bar – made of bended steel – that actuates the wheel stepping mechanism
when a key is pressed. In later models, the base plate and the
bar were cast in a light metal alloy.
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Enigma D is the first machine with a hinged top lid, which makes it
easier to access the rotors and alter the settings. The lid is held in
place by two retaining bolts, just above the keyboard.
The image on the right also shows the construction of the lamp
panel. It consists of a metal plate with 26 circular holes – one for each
letter of the alphabet – to which 26 rings are soldered. It acts as a mask
for the 26 light bulbs of the lamp panel and the alphabet film (A-Z).
In later machines, this was also a cast in light metal.
Also visible in the image are the rotor windows.
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Although the cut-outs in the top lid are oval shaped, the
actual window panes
– mounted at the upper side of the lid – are circular.
Note that these circular window panes are not present on the A320.
It is possible that they were originally
present, but were removed for some reason.
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Opening the lid provides access to the machine's interior, which
consists of the lamp panel, the battery compartment, the power selector
and the rotors. The rotors can be released by putting the
rotor locking lever in the
upright position, after which the UKW can be
shifted to the left and the three cipher rotors –
fitted to a common spindle
– can be lifted from the machine. This reveals the stepping mechanism
as shown in this image.
The UKW (on the left) can be
removed from its axle.
The ETW (on the right) however, is
permanently wired and can therefore not be removed.
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The rotor stepping mechanism consists of
three spring-loaded stepping levers,
that are actuated by the large stepping bar underneath the keyboard.
Each stepping lever has a triangular-shaped tip at the top, but the rightmost one
is narrower than the other two. It drives the sawtooth ring (ratchet) of the
rightmost rotor, as a result of which it advances by
one step on each key press.
The other two stepping levers move in tandem
with the rightmost one, but can only drive the corresponding rotor
when its triangular tip engages with the
triangular cut-out (i.e. the notch)
of the rotor to its right. This principle is known as Enigma Stepping,
and has the inherent property that the middle rotor can make an extra
step on two successive key presses.
This so-called
double stepping anomaly
was described in 1997 by David Hamer [13].
It marginally reduces the machine's
key space and the cipher period, but the effect is not as dramatic as it may seem.
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June/July 2024
The Enigma D with serial number A319 – featured on this page – was acquired
at an auction in Florida (USA) in February 2024. Judging by the photographs
of the auction house, it was in good condition – especially for its age –
but it was uncertain whether it would be in working order.
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As soon as it arrived, we closely inspected it. The case was complete,
but had green stains at the front,
probably from a leaking paint can.
It was clear that this had happened many years ago, probably when the
machine was stored in an attic or garage.
Furthermore the lock was badly damaged
and the mating pin – which
normally resides in the case lid – was missing. We later learned that it
was broken off and got stuck in the lower part of the lock, where it blocked
the lock's mechanism. Apparently someone had attempted to open the lock
with excessive force, as a result of which it was now badly damaged.
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The machine itself was in very good condition, especially if you realise
that in two years time it will be 100 years old. We already knew that the
power knob was missing and that the lamp film had deteriorated and shrunk,
to the point where some of the letters were
barely visible.
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It was decided to replace the lamp film with an
accurate replica that
we created especially for this machine. The original film will be
kept as proof of its genuine origin,
but is safely packed. Acetate films
of this type may emanate potentially harmful gasses, even after so
many years.
The machine itself appeared to be in excellent condition. After a bit
of superficial cleaning, replacing a couple of broken and missing lamps,
and inspecting the battery contacts, we used the power supply unit (PSU)
in our lab to apply 4.5V DC with a constant current of 200 mA.
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Most keys and lamps worked straight away, even without cleaning
the rotor contacts. Again, not bad for a machine of this age.
All three cipher rotors had paper rings
with numbers (1-26) glued to
both sides, as an index to the contacts. We assume this was done for some
kind of analysis. Judging from the paper, the ink, the handwriting
and the glue, this appears to have been done a long time ago, probably shortly
after the machine was purchased in 1926. As these paper rings
are part of the machine's history, we decided to leave them in place
and treat them carefully.
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It was decided not to treat the green paint stains at the front of the
wooden box, as in that case we would also loose the original serial number which
is stencilled at the front, just below the lock.
The lock was removed and,
with help from Austrian collector Günter Hütter, taken apart, reworked,
straightened and reassembled.
Even a new mating pin
for the case lid was machined.
Whilst the machine was outside the wooden case, its side panels
were rejoined with a bit of fresh glue.
At the same time,
the broken leather carrying strap was
replaced by a good reproduction.
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Scratches near the cut-out for the knob, reveal that previous owners
made a mistake with this more than once.
In later models, like Enigma K and Enigma I,
this was solved by
permanently fitting the knob to the top lid,
and driving the power selector indirectly with a
notched disc.
Another weakness in the design of the power selector is the
metal plate
shown in the image on the right. It covers the shafts of the power selector
and the two external power terminals. It is held in place by springs
around the shaft of the power selector and around the power terminals.
They are used to press the plate against the lid.
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Unfortunately, the plate and the springs are made of metal and can therefore
cause a short-circuit between the shaft and the power terminals. To prevent his,
a piece of
Pertinax (Paxolin) is fitted to the bottom of the plate.
In our case however, the springs had been deformed somewhat, as a result of which
they could bypass the pertinax and make contact with the metal plate above it.
This was solved by reshaping the springs of the power terminals
and replacing the other one.
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- Green stains on the wooden case, especially at the front
- Verneer on top lid shrunk
and loose Case glue deterioration, especially in the corners Case lock damaged, mating pin broken Power selector knob missing Screw missing from lamp panel Lamp film shrunk and deteriorated Spare light bulbs missing Leather grip broken Occasional short-circuit on battery terminals - Bad contacts between rotors
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- Exterior superficially cleaned
- Wooden case treated with protective oil
- Veneer on top surface fixated
- Case corners glued
- Interior cleaned
- Rotor contacts cleaned
- Lamp film replaced
- Missing screw added to lamp panel
- Leather grip replaced
- Case lock repaired, straightened and cleaned
- Spare light bulbs added
- New power knob machined, painted and fitted
- Springs below power terminal cover plate reshaped (one replaced)
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Enigma D is known under the following names:
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- Enigma D 1
- A26
- Ch.8
- Commercial Enigma 2
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Although this was the logical type number — D follows after A, B and C —
this name was never used by ChiMaAG in official correspondence. Instead
they used the machine's model number (A26). It is assumed that model numbers
were first introduced in 1926, starting with the A26.
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Not to be confused with Enigma K (A27), which was also known as
'Commercial Enigma'.
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A316 Prototype for Reichswehr — evolved into Enigma I A317 Prototype for Reichswehr — evolved into Enigma I A318 ? A319 ? A320 GC&CS (UK) — used for analysis by Hugh Foss in 1927/28 A323 Navy, Admiralty (UK) A324 AB Cryptograph, Sweden 1 A325 AB Cryptograph, Sweden 2 A326 ? A327 STAB, Sweden A328 STAB, Sweden A338 France A343 STAB, Sweden A344 STAB, Sweden — analysed by Damm 3
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Later displayed at the Hagelin museum at Crypto AG in Zug (Switzerland).
Current whereabouts unknown.
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The A325 is shown on the first page of the
instruction booklet [A].
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A344 was analysed by Arvid Gerhard Damm of the AB Cryptographs company,
in 1927, when he was in Paris (France) [10][11].
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A319 Crypto Museum, Netherlands A320 GCHQ, Bletchley Park Museum, UK A324 Crypto AG internal museum, Zug, Switzerland ← current whereabouts unknown A327 TSS, The Signal Regiment, Enköping, Sweden A343 Believed to be in a private collection, Sweden (2019)
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The following people have contributed to this page
and/or the restoration of the A319:
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- Günter Hütter
- Anastasion Pingios
- Paul Reuvers
- Jacub S.
- Marc Simons
- Frode Weierud
- Anders Wik
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There are different versions of this booklet. The machine shown on the
first page is probably an Enigma D (A26), whilst the machine shown
in the fold-out at the back, is the later Enigma K (A27).
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- Frode Weierud, Personal correspondence
Enigma serial number research. Forthcoming publication.
September 2022, February 2024.
- Chiffriermaschinen AG, Enigma booklet
Instruction booklet with images.
- Jakub S., Personal correspondence
September 2022.
- Kelsey Griffin, Image of open Enigma A320
Bletchley Park, Security Conference, 2010.
- F.L. Bauer, Decrypted Secrets - Methods and Maxims of Cryptology
ISBN 978-3540668718. 1 January 2000 (2nd edition). p. 113.
- Hugh Foss, The Reciprocal Enigma 1
TNA, HW25/14. Undated, but probably 1927/28.
- GCHQ, Signage near display case in internal museum
Brief account of the purchase of A320 and
Hugh Foss' analysis.
Twitter, 14 September 2021.
- Anastasios Pingios, Transcription of A320 description
Transcription of barely readable A320 description in GCHQ display case [7].
15 September 2021.
- Anders Wik, The First Classical Enigmas,
Swedish Views on Enigma Development 1924-1930
Histocrypt Proceedings, 15 May 2018.
- Arvid Gerhard Damm, Memorandum about Enigma
In reference to a letter from AB Cryptograph,
dated 5 April 1927 (Swedish).
Paris (France), 11 April 1927.
- Arvid Gerhard Damm, Preliminary statement regarding glow lamp cipher machine Enigma
Preliminärt utlåtande angående "Glühlampen-Chiffriermaschine Enigma" (Swedish).
Paris (France), 1 August 1927.
- Hugh Foss, Reminicences on Enigma
1949. Published in Chapter 3 of the book Action This Day.
Michael Smith & Ralph Erskine, 2001. ISBN 978-0-593-06357-6.
- Enigma: Actions Involved in the 'Double Stepping' of the Middle Rotor
David H. Hamer.
Cryptologia, Volume XX, Number 1, January 1997. Author's copy.
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Document kindly provided by Frode Weierud [1].
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© Crypto Museum. Created: Monday 14 September 2009. Last changed: Monday, 12 August 2024 - 14:52 CET.
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![Enigma D with S/N A320 now on display at BP [3]](img/A320_BP_JS_thumb.jpg "image # A320_BP_JS.jpg")
![Enigma D with S/N A320 [4]](img/A320_open_thumb.jpg "image # A320_open_large.jpg"){kind=small}
![Enigma D with S/N A320 now on display at BP [3]](img/A320_BP_JS.jpg)
![Enigma D with S/N A320 [4]](img/A320_open_large.jpg)
