The B-21 was the first cipher machine developed by Boris Hagelin.
He designed the machine in 1925 when he was working for the company
A.B. Cryptograph of Arvid Gerhard Damm in Stockholm (Sweden).
The B-21 was in production for many years, even after WWII when the company
had moved to Switzerland. It was available in many different versions and
At the request of the invenstors - the Nobel family - Hagelin was placed in
the company in 1922 as a controller. From 1925 onwards, Hagelin was the
acting director, whilst Damm was persuing business in France.
When the Swedish Army wanted to buy Enigma machines
in 1925, Hagelin proposed his own machine: the B-21.
It was based on Damm's initial patented design of the B-18,
using two coding wheels. Hagelin improved the design by adding two of his
famous pin-wheels to each of the coding wheels
Over the years, the design of the B-21 was changed and improved a number of
times. The image above shows one of the first versions and was probably
conceived in 1927, or shortly thereafter, as it still carries the original
company name: AB Cryptograph. It is battery powered and is
likely to have been modified at least once during its lifetime, as the relays
have been replaced by a large diode array.
It was delivered to L.M. Ericsson (the phone company)
for use by its subsidaries in South America,
hence the presence of the Ericsson label
on the wooden transit case.
At the request of the French Army, an improved version of the B-21,
the B-211, was developed. It featured a printer instead of
the light bulbs. Eventually, the developments for the French Army led to a
range of power-less designs, the so-called C-machines, starting with the
At first glance,
it resembles the German Enigma machine.
It has a similar keyboard, is battery powered and uses a lamp panel for its
output. But that's where the similarity ends.
In order to avoid patent infringement, Hagelin used a completely
different operating principle. Rather than using alphabet substitution,
he used coding wheels to scramble an n x m matrix.
Although the original patent  describes a 4 x 5 matrix, the actual
machine had a 5 x 5 matrix. This allowed only
25 letters to be used (5 x 5). This was solved by replacing the letter W
with VV (2 x 'V').
Another difference with the Enigma was that the coding wheels were stepped
irregularly, whereas most of the Enigma variations featured regular stepping.
According to Hagelin, this made the machine far less predictable.
The B-21 was therefore considered more secure than the Enigma.
Although the latter isn't true - Arne Beurling of the Swedish Cipher Bureau
broke it in 1931 in less than 24 hours
- it was good enough for its time
and it was Hagelin's first commercially successful machine.
Many of his later machines would adopt the pin-wheel principle.
The design of the B-21 is based on an earlier patient by Arvid
Gerhard Damm, modified by Boris Hagelin in 1925. It is based on
two electrical coding wheels and four so-called pin-wheels that
control the stepping of the coding wheels.
Although the actual circuit is far more complex, the simplified
circuit diagram below shows the situation when the machine is
in Ciphering Mode.
The keyboard consists of a mechanical matrix and two groups of
five electrical switches each. Pressing a key activates one switch
in each of the two groups. It also turns on power by activating
the ACT-switch for the duration of the key-press.
One group of switches is connected to the negative pole of the
battery (rows, marked 1 to 5). The other group is connected to
the positive pole (columns, I to V).
Each of the signals in then fed through a coding wheel, followed
by a programmable matrix. The outputs of the two programmable
matrices are then used to active a lamp on the lamp panel matrix.
In order to avoid current through all of the lamps, a diode is
connected in series with each lamp. In the (modified) B-21 shown here,
the diodes take the form of an
array of selenium diodes
at the right hand side of the machine.
In the initial version of the B-21, relays were used instead.
The layout of the lamp-matrix is identical to the layout of the
The machine described in the circuit diagram above is not reciproke.
For deciphering, a complex system of contacts and wires is used to
reverse the operation of each of the coding wheels and matrices.
This is mainly done by means of a cleverly designed switching mechanism,
controlled by a knob at the left,
that is combined with the slide contacts of the two coding wheels.
The image on the right shows a complex system of brushes and contacts
that form in fact five cross-switches. When in ciphering mode, the rearmost
brush contacts are touching the rings of the coding wheel.
The frontmost contacts are disengaged and are instead connected to a
fork-contact immediately below it.
The contacts are moved in tandem with the contacts of the other
coding wheel, so that they are always switched simultaneously.
Contrary to the Enigma,
the coding wheels are fixed in place and cannot be removed or replaced.
Adding the cross-switches to the simplified circuit diagram
above, results in the slightly more complex
circuit diagram below.
This diagram is also available for download at the bottom of this
The diagram shows the machine in Ciphering mode.
Switching to Deciphering, by rotating the C/D knob to the D-position,
reverses the path through each of the coding wheel/matrix
combinations. The operation of the cross-switches is illustrated at the centre.
Whether or not the selenium diodes are original parts
remains to be seen. In 1925, when the B-21 was developed,
selenium diodes had not yet been invented. Furthermore, Boris
Hagelin describes in the Hagelin Story
that he used electric relays in the initial design.
It is quite possible however, that the machine was overhauled
for diode-operation at a later date.
Later version of the B-21
The images below were taken in Basel (Switzerland) in 2008, during the
presentation of the book Mythos Enigma by Dominik Landwehr.
Hagelin's first employee Oskar Stürzinger was present as the meeting and
demonstrated some historical Hagelin machines, including a variant
of the B-21.
As becomes clear from the image on the right, the mechanical parts are
identical to the machine shown above, but electrically it is somewhat
different. The programmable matrix has been removed and is now situated
behind the coding wheels as a series of 10 plugs.
The space at the right (where the matrix used to be)
is taken up by a mains transformer.
The serial number plate at the front shows the manufacturer name
A.B. Ingeniörsfirman Teknik, which was the name of the company
after it was taken over by Boris Hagelin in 1932.
This particular machine is quite different from the one at the top of this
page, but carries the designation B-21 nevertheless.
The layout of the keyboard and the lamp panel is different and was probably
tailored for the Swedish language.
It features the standard Latin alphabet, but the letters W, X and Z
have been omitted. Instead, keys for Sk and Me have been added,
resulting in the maximum number of 25 keys.
Strangely enough, the layout of the lamp panel is different.
In the image, there is no sign of a relay bank or a diode array, but it is
entirely possible that this is hidden under the lamp panel. The machine was
mains-powered and the external mains cable was present.
At the time, we were not able to investigate this machine any further.
A later variant of this machine is the B-211, which had a built-in
printer and was motor-driven. This machine became very popular in
France where it was used extensively during the Algerian war (1954-1962).
It was built in France by an Ericsson subsidary in Colombes (Paris)
under licence from the Hagelin company in Sweden.
The popularity of the machine within the French Army
and the reliability of the company, later led to
the development of the portable C-35.
The image on the right was taken from Boris Hagelin's personal memoires .
It shows a B-211 without its top cover. The machine has the same outer
dimensions as the B-21. At the left are the well-known cipher wheels and
the pin-wheels. At the right is a printing device, with a print head sticking
out at the front panel. A paper strip is guided alongside the print head.
Like the B-21, this machine uses a 5 x 5 matrix with a total of 25 letters.
Nevertheless, the keyboard exhibits 29 keys. The function of the extra keys
is currently unknown.
The success of the B-211 did not go unnoticed.
Just before the outbreak of WWII, Boris Hagelin was forced (by the Swedish
authorities) to sell two B-211 units to the Russian Embassy.
The Russians took the design and copied the machine.
At the same time they converted the 5 x 5 matrix into
a 5 x 6 one, in order to accomodate more characters. It allowed 30 letters
of the Cyrillic alphabet to be used (the full alphabet has 33 letters).
They called the machine K-37 .
The image on the right shows a top view of the Russian copy of Hagelin's
B-211. The design of the cipher unit at the left is nearly identical to
that of the B-21. The leftmost cipher wheel has 5 contacts (like the original)
but the rightmost one has 6 contacts, resulting in 30 letters.
The printer has been adapted for 30 characters. It has been moved to the center
of the machine, with the print head sticking out in the middle, just above
the keyboard. With its 30 keys, the keyboard supports the most frequently used
letters of the Cryillic alphabet (3 are omitted).
At the right rear is the electro motor that drives the printing mechanism.
In front of the motor are 12 relays that are used for driving the rows and
columns (5 + 6). The function of the 12th relay is currently unknown.
The image above was taken from Boris Hagelin's personal memoires .
Click it for a larger view. Any additional
information about the Russian B-211 would be appreciated.
- Boris Hagelin, 100 Jahre Boris Hagelin 1892-1992
Memoires of Boris Hagelin (German).
Crypto A.G., Crypto Hauszeitung Nr. 11, September 1992.
- Boris Hagelin, The Story of Hagelin-Cryptos
Crypto A.G., Zug, Spring 1981. Based on .
- Bengt Beckman, Arne Beurling and the Swedish crypto program during WWII
2002, American Methematical Society (English translation).
(Original publication 1996.)
- US Patent US1846105
Hagelin's patent for the B-21 filed in the US in 1928.
- Paul Reuvers, B-21 Dircuit Diagram
Crypto Museum, 2010.
- Boris Hagelin, Die Geschichte der Hagelin-Cryptos
Original manuscript by Boris Hagelin in German language. Zug, Fall 1979.
- TICOM I-58, Interrogation of Dr. Otto Buggisch of OKW.CHI
8 August 1945. Declassified. p. 5.
- VV Babievsky, LS Butyrsky, DA Larin; Soviet cryptographic service 1920-1940
Website Agentura.ru (Russian).
Retrieved June 2012.
- German Patent DE430599
Aktiebolaget Cryptograph, Stockholm, 24 July 1925. 1
Thanks to Arthur Bauer for bringing this to our attention. November 2012.
Any links shown in red are currently unavailable.
If you like this website, why not make a donation?|
© Copyright 2009-2013, Paul Reuvers & Marc Simons. Last changed: Tuesday, 06 November 2012 - 14:26 CET