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M-125 (Fialka)
USSR rotor-based cipher machine

The M-125, codenamed Fialka, was a cipher machine developed by the USSR during the Cold War, shortly after WWII. It was first introduced in the late 1950s and soon became one of the favorite machines of the Warsaw Pact countries. Fialka remained in use until the early 1990s.
The fall of the Berlin wall in 1989, marked the decline and finally the collapse of the Soviet Union. With the retreat of the Russians from the countries behind the Iron Curtain, the remaining Fialka machines were taken back and have subsequently been dismantled or destroyed.

Each country of the Warsaw Pact had its own customized Fialka version, adapted for the local language. This means that each country had its own keyboard and print head. Furthermore, the wiring of the coding wheels was different for each country. The rest was identical.

Most machines were capable of communicating either in Latin or Cyrillic (Russian) writing. Although the Latin alphabet was specific for each country, the Cyrillic alphabet had no punctuation marks and was identical on all machines, making them interoperable when a mutual set of wheels was used. A standard — Russian-only — version also existed.
Different sets of Fialka wheels Wheels Punched cards as part of the Fialka's daily key Key card Canvas wallet with various Fialka tools Tools Moisturizer for gluing back-gummed paper tape Glue Fialka Test Device Test unit

Fialka is a Russian word that means 'Violet'; a rather nice small flower. Around 1965, the Russian Army introduced a brand new cipher machine, which was given the codename FIALKA. Two versions of this machine are known to exist: the M-125-xx and the M-125-3xx, with country-specific variants of each model. In principle, the machine is called M-125, whereas Fialka is the name of the cipher procedure. However, as the machine is now commonly called Fialka, we will use that name on this website.

The design of the Fialka is largely based on the well-known Enigma machine, that was used by the German Forces during WWII. Like the Enigma, it uses a number of coding wheels to scramble the letters typed on the keyboard. With each key-press, the wheels move into a new position, thereby effectively changing the alphabet-substitution for each letter typed on the keyboard. And that's where the similarity with the Enigma ends.

Rather than presenting the output on a lamp panel, the Fialka prints the coded letter directly onto a paper tape. At the same time it can punch the letter into the same paper tape in a 5-bit digital code, much like the baudot code of a teletype machine. In addition, the Fialka contains a paper tape transmitter which can be used to transmit or duplicate a message. The Russians have clearly learned from the flaws in the Enigma's design and its operating procedures, as they've implemented the following improvements:
  • 10 wheels, rather than 3 or 4 on the Enigma,
  • More frequent wheel turn-overs,
  • Adjacent wheels move in opposite directions,
  • Wheel wiring can be changed in the field (from 1978 onwards),
  • A punch card is used to replace the Steckerbrett,
  • A letter can be encoded into itself (impossible on Enigma).
In addition to this, the following extra features are available:
  • The use of letters, numbers and punctuation marks (M-125-3 only),
  • Can be used to duplicate a punched-paper tape,
  • Can be used as a standard teletype machine (i.e. generate plain-text),
  • Supports both Russian (Cyrillic) and Latin.

Frontal view of an M-125-3xx Fialka Typical view of an M-125-3xx Fialka machine View of the wheels inside the Fialka The wheelset outside the metal container Close-up of the contents of the container A typical set of non-adjustable (fixed) wheels. A set of 2 identical key cards A typical Fialka setup

Different models
Many variants of Fialka exist, but basically, there are only two different models: an early version and a later - improved - version. It is very easy to tell the difference as they both have a different keyboard. The keyboard of the older model, the M-125-xx, is shown on the left. It has rounded keys with two letters (cryllic and latin) on them. The newer M-125-3xx has square keys with 4 characters on each key top (shown on the right).

Each of these basic models came in a variety of versions, mainly tailored to the specific language of the country where it was used. All version have at least the basic Latin and Cyrillic (Russian) alphabets, and the later M-125-3xx models also contained a third, country-specific, alphabet.

Not only the keyboard was different for each country, the print head of the later models was also country-specific. Furthermore, the coding wheels were wired differently for each country. The rest of the wiring of the machine is identical for all versions.
The initial version of the machine was given the designator M-125 and had rounded keys with 30 letters of the Cyrillic (Russian) alphabet. It had a rotating print head with just the 30 Cyrillic characters on its circumfere.

Later versions of the machine (M-125-xx) had a keyboard with two letters on each of the keys. The leftmost letter was from the Cyrillic alphabet (green) whilst the rightmost one was a Latin character (red). The print head was changed to support both alphabets and a toggle switch on top of the machine was used to choose between the two alphabets.
At some point, the machine was completely overhauled and improved and a new version, the M-125-3xx, was introduced. The machine had square keys, with 4 characters on each of them, allowing the use of Latin, Cyrillic and country-specific letters as well as puctuation marks and special characters. For this, two different print heads were supplied: one combined Cyrillic/Latin printhead and one for the country-specific alphabet that also had punctuation marks and special characters.

Each coutry of the Warsaw Pact had its own national version of the M-125-3, and the 'xx' suffix was used to determine the country/version. The above drawing shows two examples of such country-specific versions. The one on the left is the Polish version of the machine (M-125-3MP3). The one on the right is the Czech version (M-125-3MP2).

These machines had thee modes of operation:
  1. Letters only
  2. Numbers only
  3. Mixed (i.e. the full alphabet)
These modes were selectable with a text-mode-selector at the rear of the machine. In the 3rd mode the machine was not compatible with the older M-125 machines. When this mode was selected, the leftmost key on the middle row was used to switch to numbers and punctuation marks (1...), whilst the rightmost key on the same row was used to toggle back to letters (A...).
Technical details
The Fialka is a very complex mechanical and electrical machine. If you want to known exactly how it works, you will find detailed information in the links below. If you want to know even more, check out the Reference manual further down this page.

Fialka wheels
The Fialka has 10 unique coding wheels, each identified with a letter of the Russian alphabet. The wiring can be swapped between wheels and each wheel contains an arbitrary number of turn-over notches. Furthermore, each country of the Warsaw Pact had its own set of 10 wheels.

 More information
A typical set of Fialka wheels. Click for detailed information.

Key cards
Apart from changing the settings of the wheels, the daily key also involved the insertion of a unique key card in a drawer on the left of the machine. The key card was used instead of the Steckerbrett of the original Enigma design.

The key card gives less room for mistakes a patch panel, and also increases the number of possible permutations.

 More information
Original Fialka key card

Test Device
For repair and maintenance a special Fialka Test Device was available. The device was connected to the special test connector at the left side of the machine.

As the test device has never been found so far, we can only speculate about its functionality. It is likely that the device contained a paper tape reader to allow several test programs to be run.

 More information
Test connector

According to the checklist that came with a Fialka machine, each machine was supplied with a small toolkit that was used for daily maintenance and small repairs. It contained tools to adjust the machine and to remove paper from a blocked machine.

 More information
Unfolded toolkit

Reference Manual
The history of the M-125 Fialka is still very clouded and very little is known about its history, its use and its backgrounds, as the machine was in use until recently. Although the Russians have done their best to destroy the remaining machines once they were decommissioned, a handful have miraculously escaped demolition and are now in the hands of collectors and museums.

In the mid-2000s, a limited number of M-125 Fialka machines appeared on the European surplus market and have since become highly wanted collector's items. Although Fialkas were in use in all countries of the former Warsaw Pact, the machines that have survived all come from Poland and Czechoslovakia. So far, we haven't found any of the other machines.

When we first found a Fialka machine in 2005, no information about this machine was available on the internet or elsewhere. So, we decided to reverse-engineer the machine and re-create the circuit diagram from scratch. All we had to start with was a German Operator's Manual and a working machine. Luckily, we were given a broken surplus machine that we could take apart.

The result is a 140+ page manual with hundereds of drawings, photographs and circuit diagrams. The manual is available only in printed form and can be ordered directly from us. Each copy of the manual is printed in full-colour and contains the full circuit diagram.

 More information
Fialka Simulator
Version 5.06 - 7 December 2012

Russian programmer Vyacheslav Chernov (Чернов) has written a beautiful graphical simulator for Windows TM, that emulates all known Fialka models and countries.

It supports the old wheels as well as the later adjustable wheels, and supports different wheel-wirings for the various countries. Furthermore, the wiring cores can be installed, flipped and rotated in any of the other wheels.

 Download Fialka Simulator
 How to set the keys (and card)
Filaka Simulator for Windows. Click the image to download the program as a RAR-file.

Other simulators
  • Java Applet (experimental) by Eugen Antal (off-site)
    This is a fully functional non-graphical Fialka Simulator that is written in Java and runs on virtually any platform, including Windows, Apple Mac, Linux and Unix. Instructional videos are available as well.

Below are some files that are available for download. Please note that these files are supplied 'as-is'. Crypto Museum can accept no responsibility for these files or their suitability for any purpose.
  • XML files for software Simulator authors 0.01
    This is a ZIP archive, containing a set of XML files that describe all features of the Fialka and its wheels. These files can be used by software writers when creating, for example, a Fialka Simulator.

  1. Paul Reuvers & Marc Simons, Fialka Reference Manual
    2005-2009. Release 2.0, 22 June 2009.

Further information

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Copyright 2009-2013, Paul Reuvers & Marc Simons. Last changed: Friday, 07 December 2012 - 18:06 CET
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