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M-125   Fialka
Basic Fialka cipher machine

The M-125, codename FIALKA (Russian: ФИАЛКА), was a Russian electromechanical wheel-based cipher machine, developed during the Cold War by the USSR in the late 1950s. It features 10 electrical coding wheels, with 30 contacts at either side, that move in alternate directions.
 
The machine has a card-reader at the left that acts as an extra (static) wheel. It consists of a 30 x 30 contact matrix and allows its permutations to be altered as part of the daily key. The card reader is comparable to (but cryptographically stronger than) the plugboard of the Enigma.

Like the Enigma, the electric current enters the wheels from the right via a static disc (the entry) wheel. The current path is returned through the wheels by means of a reflector at the left. Unlike Enigma however, on which a letter can never be encoded into itself, Fialka features a clever 'magic circuit' (German: Dreipunktschaltung) that does allow a letter to be encoded into itself.

Nation-specific variants were made for the various countries of the Warsaw Pact. These had keyboards and print heads that were adapted for the local language. Furthermore, the cipher wheels had a country-specific wiring, so that during piecetime the various countries could not communicate with each other using Fialka.
  
M-125 Fialka with open top lid

The M-125 contains a paper tape puncher, a printer and a paper tape reader. Furthermore it has a digital 5-bit data output at the right rear, that can be used to drive a telegraphy system or a transmitter directly. It can also be used for adding extra security to the system, by connecting it to the advanced TEMPEST Power Supply Unit (PSU). Two different power supply units are known to have been issued with Fialka machines: a standard PSU and a TEMPEST compliant version.

The M-125 was succeeded in the late 1960s by the M-125-3, which is basically an improved - backwards compatible - version of the M-125 with support for extended character sets. Nevertheless, the M-125 stayed in use for a number of networks, right until the end of the USSR.
 
M-125 Fialka with open top lid Fialka M-125 (old version with rounded keys) M-125 Fialka with open card reader Fialka M-125 with copy holder raised Paper tape properly loaded Looking into the wheel transport mechanism after the wheels have been removed The 10 cipher wheels inside the M-125 (Fialka) Two cipher wheels taken off the spindle
M-125 front view M-125 rear view M-125 right view M-125 left view M-125 Fialka showing its 10 cipher wheels Removing the wheels from the machine The wheels removed from the M-125 Close-up of the keyboard

 
Country-specific variants
The base of the machine (and the internal wiring) was the same for all countries of the Warsaw Pact, but for each country a customised version of the Fialka was issued, identified by a suffix to the model number (e.g. M-125-MN for the DDR). This involved the layout of the characters on the keyboard, an extra print head and the country-specific wiring of the cipher wheels. So far, the following country-specific variants have been identified:
 
  • Poland
  • Czechoslovakia
  • DDR (East-Germany)
  • Russia
  • Hungary

Controls
The M-125 Fialka was a mechanically complex, jet easily controllable, electromechanical cipher machine. It had only two electrical connections, one at the left and one at the right. All controls were conveniently spread over the body of the machine. After connecting the machine to the Power Supply Unit (PSU), it was switched ON by placing the ON/OFF switch in the БКЛ.-position.

M-125 Fialka seen from the front right

The 30-character keyboard is located at the front of the machine, with a black spacebar in front of it. When typing a message, a copy holder can conveniently be raised to hold the message form. A ruler holds the form in place and can be used as a pointer by moving it up and down. At the front right is a paper tape reader that is mechanically coupled to the keyboard. It is used to play back previously recorded messages. To the right of the copy holder is the MODE selector.

M-125 Fialka seen from the front left

The image above shows the machine as seen from the front left with the copy holder lowered. At the left of the machine is a drawer that can be opened. It holds a punched paper card that is part of the daily key settings. A resettable counter at the front left is used to count the number of characters that are entered. At the right rear is a combined printer/puncher.
 
Mode of operation
A three-position lever in the large red circular 'blob' to the right of the drum, is used to select the required mode of operation. It is called the MODE selector and is used to select between Coding, Decoding and Plain Text. The settings are explained in the following table:
 
Label Russian Phonetic English
О Открытый Текст Otkrytyj Tekst Plain text
З ЗашифроватЬ Zashifrovat Cipher
Р РасшифровыватЬ Rasshifrovyvat' Decipher
ПФ Перфорация Perforacija Punch 1
ПЧ Печатание Pechatanije Print 2

The lower two entries in the above table are the settings of the Print/Punch control lever, that is located to the right of the MODE selector and is part of the same red 'blob'.
 
  1. Please note that in Punch mode (ПФ) the printer is also enabled. This means that the paper tape will contain punched data as well as printed text. Printing can not be disabled on the M-125.
  2. Set the Print/Punch selector to Print (ПЧ) to disable the puncher. This setting is needed when narrow 10 mm paper tape is used.

Russian/Latin
The basic Fialka machine supports 30 different characters and was designed for the Russian language and the Cyrillic character set. As Cyrillic has more characters than Latin, the usual 26 characters were not sufficient. In order to avoid mechanical complexity of the electric wheels, the 30 most frequently used Cyrillic characters are used. These are the following characters:

А Б В Г Д Е Ж З И К Л М Н О П Р С Т У Ф Х Ц Ч Ш Щ Ы Ь Ю Я Й

On each Fialka machine, regardless the country in which is was used, these 30 characters are always at the same position on the keyboard and on the print head. As the same characters are used to identify the position of a cipher wheel, we will use these Cyrillic letters as the reference.

Evolution from Russian keyboard to Russian/Latin keyboard.

On the international version of the M-125, it is possible to switch between Russian and Latin. For this, two letters are printed on each key top: a Cyrillic one in green (left) and a Latin one in red (right). The position of the Latin characters varies per country. Numbers were not present on the keyboard and had to be typed in full (e.g. in German: 'dreisieben' instead of '37').
 
Cipher wheels
The M-125 uses 10 cipher wheels, each of which has 30 flat-faced electrical contacts at one side and 30 spring-loaded contacts at the other side. The 30 positions of each wheel are marked with the 30 letters of the Russian alphabet, in clockwise order (when viewed from the entry disc):

А Б В Г Д Е Ж З И К Л М Н О П Р С Т У Ф Х Ц Ч Ш Щ Ы Ь Ю Я Й

Each of the 10 cipher wheels is wired differently and has a number of pins at the outer rim that are used to control the stepping of the wheel next to its neightbour. The number of pins and their position are different on each wheel. Each of the 10 wheels is identified by a letter of the Russian alphabet which is engraved in its right side. The following 10 letters are used:

А Б В Г Д Е Ж З И К

The 10 wheels are mounted on a spindle and are held in place by a retaining clip. The spindle is then placed inside the machine. Each machine came with two identical sets of wheels: one inside the machine (the operational set) engraved with black letters, and a spare one with red engraved letters in an aluminium container inside the dust cover. The wheels were numbered sequentially.
 
The image on the right shows the operational wheels, two of which (K and E) are removed from the spindle, with the spring-loaded contacts (i.e. their right side) facing upwards. The И-wheel is just visible at the right end of the spindle.

Each wheel is wired differently in a fixed pre-determined pattern that can not be altered in the field. The wiring can be accessed by removing the metal disc at the left side of the wheel, using a special tool or just by pressing and rotating the disc with the fingers. The wiring was different for each country of the Warsaw Pact.
  
Two cipher wheels taken off the spindle

When looking at the wheels from the top of the machine, the odd wheels move towards the front of the machine, whilst the even wheels move towards the rear. Wheels 2 and 9 are always advanced when a key is pressed. Stepping of the other wheels is controlled by the position of the notches or pins at the rim of another wheel. This is illustrated by the drawing below:


In principle, all wheels can make a single step in each key-press, but its stepping can be inhibited by its controlling wheel. Wheel 2 controls the stepping of wheel 4. If a pin is present at a certain position, it inhibits the stepping of wheel 4. For this reason the pins are also known as 'advance blocking pins'. In the same way, wheel 4 controls the stepping of wheel 6, and so on. For the odd wheels, wheel 9 is the driving one. It controls wheel 7 that in turn controls wheel 5, etc.

 Wheel stepping in more detail
 
PROTON-2
In 1978, the standard fixed wheels were replaced by the far more advanced adjustable cipher wheels as part of the PROTON-2 directive. This allowed the wheels cores to be reversed, inserted in different positions and in different wheels. Although these PROTON-2 wheels could perfectly well be used inside the standard M-125, we have never found any proof of this. All M-125 machines that have survived have been found with the older fixed wheel sets.

As far as we know, the PROTON-2 wheels were only issued with the later M-125-3 machines. With the wheel cores in their neutral position, these wheels are backwards compatible with the older fixed wheels, allowing communication between the two Fialka models.

 The cipher wheels in more detail
 Wheel wiring in more detail
 
The operational wheel set (front) and the spare wheels in an aluminum container Spare rotor set in aluminium container The spare cipher wheels in an aluminum container Spare wheel set outside its container The standard cipher wheels (left) and the spare wheels (right) The 10 cipher wheels inside the M-125 (Fialka) Removing the wheels from the machine Two cipher wheels taken off the spindle
Getting access to the wiring core Opening the wheel The inner wiring of a cipher wheel (wiring core)
card Card reader
 
The M-125-3 has a card reader that adds an extra layer of permutations to the machine. The card reader is located at the left side of the machine and consists of a drawer that gives access to a 30 x 30 contact matrix. In many respects it can be seen as a non-moving programmable wheel. Lower the metal bar that protects the reader and firmly pull out the drawer that holds the card.
 
The permutation matrix is 'programmed' by means of a punched paper card with 30 holes: one for each row/column combination. The card is placed inside the drawer, using two alignment pins to ensure its position. Once the key card is in place, the drawer can be closed again.

Compared to the German Enigma machine, the card reader takes the place of the Enigma's Steckerbrett (plug board), but offers a stronger permutation as it is not self-reciproke. The latter is considered a cryptographic weakness of the Enigma that helped codebreakers during WWII.
  
An original Fialka key card in the card reader

As the Fialka uses a reflector, just like Enigma's Umkehrwalze, the current passes the card reader twice. In practice the punched card was part of the daily key and was changed every 24 hours. It was made of paper that was so thin that it easily got ripped, so that it could not be used twice.

 The key cards in more detail
 The card reader in more detail
 
Card reader (closed) Opening the drawer of the card reader An original Fialka key card in the card reader Closing the card reader The day number visible to a small window Reproduction card in the drawer Closing the drawer and raising the bar The metal test triangle in place

 
Printer
Unlike the WWII German Enigma machine, that presented its output on a panel with 26 lamps, the Fialka can print its output directly on a paper strip that could be used directly in a telegram. In addition, the machine could also punch the message into a standard 5-level teleprinter tape.
 
The combined printer/puncher is located at the right rear and is visible through a hole in the top lid of the machine, just behind the copy holder. The printer consists of a rotating print head with one or two rows of characters. A lift mechanism determines which of the two rows is used. The paper strip moves behind the print head from right to left and leaves the machine at the left.

In between the print head and the paper strip is a standard typewriter-style ink ribbon. When the required character is facing the paper strip, a hammer is released from the rear of the paper.
  
Print head with lift-mechanism for selecting between Russian and Latin typeface.

The hammer momentarily pushes the paper strip (and the ink ribbon) against the print head, causing the character to be printed. When using standard 5-level paper tape, the integrated puncher stores the message on the paper strip by punching out the required holes, whilst the same message is printed as text at the position of the sprocket holes (albeit at an offset).

The Fialka accepts two paper sizes. In addition to the standard 5-level teleprinter tape, it is also possible to print the text on a narrow 10 mm paper tape. This tape is entered from the rear of the machine and uses a different path to the printer, bypassing the puncher. When this type of paper is used, the tape guide (behind the ink ribbon) has to be adjusted accordingly. When pre-gummed tape was used, it could directly be glued onto a telegram sheet or message form.

 The printer in more detail
 
Print head with lift-mechanism for selecting between Russian and Latin typeface. The capstan and the Latin/Russian switch The paper chad box attached to the side of the machine Switching to Latin Switching to Russian Feeding the paper Feeding the paper through the puncher Use the capstan to transport the paper

 
Tape Reader
The M-125-3 has a fully integrated paper-tape reader that accepts standard 5-level teleprinter tape in the specific Fialka encoding standard. It is located at the front right of the machine and is mechanically coupled to the keyboard. It can be used to play back previously created messages.
 
The image on the right shows the tape reader. A small lever, just below the red button, allows the reader to be opened after which a tape can be inserted. After closing the reader, the message is played back by pressing the ПУСК button (start).

When running, the tape reader directly actuates the five coding rods underneath the keyboard, as if the keys were actually pressed. After the green ПУСК button is pressed, the tape runs until the red СТОП button (stop) is pressed or a NULL character (00000) is encoutered on the tape. The keyboard is then decoupled again.
  
Entering a punched paper tape

Although it was technically possible to connect the Fialka directly to a transmitter using the DATA output socket, this was not recommended. If the machine was accidently left in the О-position (plain text) instead of the З-position (coding), the original message would be sent in clear.

In order to avoid this risk, it was recommended that a message was first encrypted on a punched paper tape, using the built-in puncher, and then tested by reading it back through the reader using З-mode (decipher). If this did not result in garbage, the tape would be send in clear. The advantage of this method was that the encrypted tape could also be sent by separate tape transmitter that did not necessarily have to support the same 5-level encoding scheme.

 The tape reader in more detail
 
Start/stop buttons for the tape reader Opening the tape reader Entering a punched paper tape Aligning the tape Closing the drawer Selecting the required start position Start the tape reader Stopping the tape reader

 
Counters
The M-125 has a character counter at the front left that is used to count 5-letter groups. The counter is reset by pressing the large push-button at the front of the machine's base. The rightmost digit (marked with a red border) is used counts the characters and wraps around at five (1-5) whilst the remaining 3 digits are used to count the number of 5-letter groups.
 
Counting the number of 5-letter groups was an important part of the procedure as cipher text telegrams were generally sent this way. When placing the dust cover over the machine and locking it up, a bracket mounted to the front of the dust cover ensures that the large reset button is pressed before the case is closed.

This is done to ensure that the counter is always set to zero when the machine is unused. This way the counter reveals no information about the latest message that was (de)coded. This counter is also present on the later M-125-3.
  
Character counter

Counters of this type were commonly used on other Russian cipher machines of the 1960s, 70s and 80s as well, and were probably made by the same manufacturer. As an example: the cipher unit of the M-130 (Koralle) has a nearly identical (black) counter mounted at the top right.
 
Character counter Counter and reset button Resetting the counter Counter reset

 
Accessories
The M-125 was originally supplied with a number of accessories, tools and spare parts, some of which were stored inside the dust cover. Below an overview of the various accessories that were available. Click any of the thumbnails below to find additional information about the item.
 
Original check list Metal dust cover that protects the machine and is used to store some accessories Metal box for collecting paper chad from the punched paper tape Paper feeder that holds a fresh paper tape reel Small hand crank for making corrections and for releasing a blocked mechanism Test reflector Spare set of wheels in aluminium can Moisturizer for glueing pre-gummed paper strips onto a message form
Canvas wallet with various tools Spare parts and accessories
ZIP
Oil can used for maintenance User manual Standard Power Supply Unit (PSU) Tempest complient Power Supply Unit (PSU) 24V service lamp used for seting up and maintenance Metal test triangle for the card reader
Mechanical and electronic spare parts

 
Check list
When they were released by the factory, each Fialka machine came with its own hand-written checklist. It shows which items were originally supplied with the machine when it was issued to the users in the field.

Some of the items have been found by collectors over the years, but a few of them remain a mystery to this day...

 More information
  

 
Dust cover
The Fialka is an extremely compact machine, with many features efficiently cramped into a small space, and the same can be said of the dust cover that slides over the machine from the top and is retained by two locks at the front and two at the rear. It can be carried with a grip at the front.
 
The rectangular dust cover protects the machine agains dust, water and other hazards, so that it doesn't get damaged during transport.

It is also used to store some of the frequently used accessories. With a clever use of the limited available space, the designers have succeeded in storing the paper reel holder, the paper chad box, the test reflector, two spare print heads, the crank and an aluminium can with a spare set of cipher wheels. The image on the right shows how these are stored. The crank is not visible in this image; it is stored at the bottom right.
  
The paper chad box covering the spare wheel set

The dust cover is nearly identical to that of the later M-125-3. The dimensions are the same and most accessories are stored in the same place, with the exception of the paper chad box that is stored over the spare wheel container. More about each accessory below.

The dust cover also serves as a safety measure to avoid giving away strategic information. At the front of the cover is a small metal bracket that mates with the counter reset button in the bottom of the case. When re-fitting the dust cover, the counter reset button has to be pressed, before the cover can be closed. This ensures that the counter is always reset when the machine is stored, so that it no longer reveals information about the length of the latest message that was created.
 
Dust cover Inside the dust cover The paper chad box covering the spare wheel set Test reflector and crank Releasing the paper tape holder Spring-loaded stub to keep paper chad box in place Removing the paper chad box Spare wheel set

 
Paper chad box
When using the machine to store messages on a 5-level punched paper tape, the small circular punched-out pieces of paper leave the machine through a small channel at the right rear, just in front of the Data socket. The chad is collected in the paper chad box that is attached at the right.
 
The paper chad box is normally stored inside the dust cover, over the aluminum container with the spare wheel set. It is held in place by a spring-loaded metal stub that is attached to the side of the dust cover. Pull the spring upwards to remove the chad box. Now simply hang the box over the two screws at the side of the machine.

Once the box is in place, the paper chad outlet channel should be extended to avoid spilling the paper chad aside the box. When typing on the keyboard whilst a wide paper tape is present, any paper chad will now fall into the chad box.
  
The paper chad box attached to the side of the machine

 
M-125 paper chad box Inside the dust cover The paper chad box covering the spare wheel set Spring-loaded stub to keep paper chad box in place Removing the paper chad box The paper chad box attached to the side of the machine Paper chad box aside the machine Paper chad collected in the chad box

 
Paper feeder
When using the printer and or the tape puncher, the paper tape has to be fed in from the right of the machine. A suitable tape feeder is stored inside the dust cover. It consists of a square matal plate with several guides and a spool at the center. The spool accepts a fresh reel of paper tape.
 
At the rear of the machine, a short vertical metal stub is present that allows the metal tape holder to be mounted to the body of the machine. It slides over the metal stub and is retained by two metal clips at the bottom of the machine.

The paper is fed via the paper guides into a large hole in the rear right of the case in such a way that it comes out through the oval hole in the right side of the case. The paper is then fed back into this hole and inserted into the tape puncher. After feeding it in as far as possible, the capstan should be rotated to pull the tape through.
  
Paper tape feeder attached to the rear of the machine

Keep turning the capstan, until the paper tape becomes visible at the tape outlet at the left side of the machine. Fialka accepts two different paper sizes: wide and narrow. The most commonly used paper tape is the wide variant that is used for creating 5-level punched paper tape. This is the same paper that is used in Europe and in the US for storing teleprinter messages (Telex).

With Fialka, this paper can be used to punch 5-level data, print text or both. Alternatively, it is also possible to use narrow 10 mm paper tape for text only. When this tape is used, the puncher has to be swiched off by setting the print/punch selector set to ПЧ. Furthermore, the paper guide behind the ink ribbon has to be adjust for the narrow tape.
 
Paper tape holder (rear side) Paper tape holder with fresh reel of paper installed Inside the dust cover The paper tape feeder stored inside the dust cover Releasing the paper tape holder Installing the paper tape holder Locking the tape holder in place Locking the tape holder in place
Paper tape feeder attached to the rear of the machine Guiding the paper tape to the inlet Feeding the paper Feeding the paper through the puncher Use the capstan to transport the paper Metal stub for mounting the paper tape feeder

 
Crank
Each Fialka machine is supplied with a small hand crank that is usually stored inside the dust cover, in the corner behind the paper tape feeder. The crank is made of hardened steel and has a bakelite grip.

It can be inserted into a hole in the right side of the body of the machine where it is engaged with the main non-ratating driving axle. It can be used to advance or step-back the position of the wheels as part of the operating procedures or for the correction of mistakes.
  
The hand crank

 
The crank, stored inside the dust cover The hand crank The hand crank The hand crank inserted into the hole at the right Operating the hand crank Hand crank inserted into the mechanism Pushing the crank all the way in Using the crank to move the mechanism back and forth

 
Test reflector
As a troubleshooting aid for a malfunctioning machine, a test reflector was supplied that could be mounted instead of the cipher wheels, effectively eliminating the wheels. The test reflector was usually stored on a small axle inside the dust cover and was held in place by a retaining clip.
 
In order to use the test reflector, two retaining clips are needed: the one that was used to retain it inside the dust cover and the one that normally retains the wheels on the spindle.

Especially for use of the test reflector, the spindle has an extra rig engraved towards the right. The tet reflector is placed between the two rigs and held in place by the two retaining clips. The spindle is then mounted inside the machine in the usual manner, as shown in the image on the right. The white line of the test reflector has to line up with the white dot on the entry disc.
  
Test reflector mounted inside the machine

The test reflector connects the contacts of the entry disc together in pairs: 1-2, 3-4, 5-6, etc., and effectively eliminates the cipher wheels and the reflector from the cryptographic algorithm. When the machine is set to Coding or Decoding Mode (the MODE selector in the 'З' or 'Р' position) and the metal test triangle is placed in the card reader, it is now possible to trace the electric current from each key through the card reader, the entry disc and back, through to the printer.
 
Wiring of the test reflector Extra rig in the spindle used for the test reflector Spindle, test reflector and two retaining clips Test reflector mounted on the spindle Placing the test reflector inside the machine Test reflector mounted inside the machine Aligning the test reflector M-125 with test reflector in place

 
Spare wheels
Each Fialka machine came with two full sets of rotors: an operational one that resided in the machine, and a spare one that was stored in an aluminium can. In order to distinguise between the two sets, the letters on the rim of the operational set were painted in black, whilst the letters on the spare set were red. The letter identifying the wheel was painted in the alternative colour.
 
The image on the right shows a complete spare set as it was supplied with the Polish variant of the M-125-3. The wheels have red lettering with one letter (the letter identifying the wheel) in black. The wheels all have identical serial numbers (in this case: 1391) with a '3K' prefix, indicating that the wheel have Polish wiring.

The spare wheels were normally stored in a aluminium container that was kept inside the metal dust cover, where it was retained by a metal strip. The red wheels would only be used in case the operational wheels were broken or needed maintenance, which is why the quality of the red wheels is often better.
  
The spare cipher wheels in an aluminum container

The spare wheels were wired identically to the operational ones so that they could be used immediately in case of an emergency. When not in use, the wheels were all set to their basic position (i.e. the rings set to 'A' and the cores with side '1' up) and were placed on the spindle in the order of the alphabet, so that no information about a previous key was revealed.

Having a spare wheel set was also useful in case the cryptographic key was changed more often (e.g. twice each day). It allows one set to be prepared for the new key well in advance, so that it can be swapped quickly. This minimises the time the machine is 'off-line'.

 The wheels in more detail
 
Spare wheel set Aluminium can with spare wheel set Aluminium can with spare wheel set Spare rotor set in aluminium container The spare cipher wheels in an aluminum container Spare wheel set outside its container The standard cipher wheels (left) and the spare wheels (right) Standard and spare fixed wheels side-by-side

 
Toolkit
Each Fialka machine was supplied with a toolkit that was used for daily maintenance and small repairs. The toolkit consisted of an (army) green canvas wallet with several screwdrivers, wrenches, pins and hooks.

Although a toolkit was supplied with every machine, not many of them have survived, making them into desired collector's items.

 More information
  
Picking one of the tools

 
Spares kit
In addition to the toolkit, the Fialka was also supplied with a small wooden box with spare parts and accessories, or in Russian: Запасные части И Принадлежности, or ЗИП (Latin: ZIP).

The spares kit contains mechanical, electrical and electronic parts, a tape moisturizer, a spare axle, retaining clips and much more.

 More information
  
Fialka ZIP box with the lid taken off

 
Oil can
Apart from the toolkit, an oil can was supplied for maintenance. It was used to oil the moving parts of the machine, such as the axles, the bearings and the rotor spindle.

The image on the right shows the oil can that was supplied with each Fialka machine.

 More information
  
Fialka oil can

 
User manual
Each country of the Warsaw Pact had its own version of the User Manual, written in the local language. The manual explained the operation of the M-125-3, its maintanance and the cipher procedures to be followed.

The image on the right shows the East-German version of this manual, which was known in the DDR as A 040/1/321 [1].
  
M-125-3 with the German (DDR) version of the manual

 
M-125-3 with the German (DDR) version of the manual German (DDR) version of the instruction manual First page of the German manual Example of key material in the German manual The toolkit in front of an M-125-3 Picking one of the tools Using the hook to replace a spring Fialka oil can

 
Standard PSU
The image on the right shows the standard PSU, of which two manufacturing variants exist. It is the most common PSU that was used with Fialka machine and was also issued with the later M-105 (Agat) cipher machine.

The standard PSU allowed the Fialka machine to be powered from a wide range of mains AC voltages as well as from a 24V DC network.

 More information
  
Standard Fialka PSU. Click for more information.

 
Tempest PSU
Polish Fialka machines (M-125-3MR2) were issued with a very sophisticated stabilized Power Supply Unit (PSU) that contained extra circuitry to improve overall cipher security by adding extra TEMPEST measures.

 More information
  
Advanced Fialka PSU with TEMPEST feature. Click for more information.

 
Service lamp
For setting up a Fialka machine in the dark and for maintenance and repair, a small 24V service lamp was supplied as part of the spares kit (ZIP). It consisted of a bakelite grip, a metal reflector and a 24V car lamp. At the end of the cable was a 2-pin plug, similar to a mains wall plug (which is probably why so many lamps are broken).

The service lamp was connected to the 24V outlet of the Fialka PSU, either 'piggy backed' to the Fialka power cable of the standard PSU, or to the dedicated socket of the Tempest PSU.
  
24V service lamp with cable and plug

 
Fialka service lamp as it was stored Fialka service lamp 24V service lamp with cable and plug Holding the service lamp Close-up of the reflector Service lamp connected to the standard PSU by inserting it 'piggy back' to the Fialka power cable Using the service lamp Connecting a work-light to the rear of the PSU

 
Test triangle
Each Fialka machine was issued a thin metal triangle that could be placed in the drawer of the card reader, instead of the key card. At the end of the day or session, the Fialka was set to its basic position and the key card was removed and destroyed.

The metal triangle was then placed in the card reader. It forces the identity matrix (A → A), so that the machine can be used in plain text Mode.

 The test triangle in more detail
  
Placing the test triangle in the card reader

 
The metal test triangle for the Fialka card reader Holding the metal test triangle Holding the metal test triangle Close-up of the upper edge of the test triangle The text BEPX (this side up) at the upper edge of the triangle Placing the test triangle in the card reader Test-triangle in the drawer of the card reader, creating the 'unity matrix' Close-up of the test triangle in the card reader

 
Tape moisturizer
In some cases the Fialka was used to print the decoded output directly to narrow pre-gummed 10 mm paper tape, so that the message could be glued on to a message form, just like a telegram.

In such cases the tool shown in the image on the right was used to moisterize the pre-gummed tape in order to activate the glue.

 The tape moisturizer in more detail
  
Narrow tape moisturizer

 
Spare parts
In addition to the Spare Parts and Accessories Box (ZIP) shown above, various other parts and building blocks were available for an authorised repair centre.

Apart from the usual mechanical, electrical and electronic components, complete building blocks were available, such as the 5-bit encoder diode matrix, the puncher driver and the famous magic circuit.
  
A collection of Fialka spare parts taken from the ZIP

 
A collection of Fialka spare parts taken from the ZIP Close-up of some spare parts Transistor for the puncher driver Bottom view of the magic circuit (new version) Top view of the magic circuit (new version) Puncher driver (top view) Diode matrix (contact side) Diode matrix (5-bit encoder)

 
5-level paper tape
The M-125 can read and punch standard 5-level paper tape, just like many western telegraphic devices of the era, but uses neither the standard Baudot encoding nor its Russian variant for this. Instead, the machine uses a proprietary encoding that was only used for Fialka and for the later M-105 (AGAT) one-time tape machine. The 5-bit alphabet is illustrated in this diagram:

Proprietary encoding scheme used for 5-level punched paper tape

With 5 holes it is possible to create 25 = 32 different combinations. 30 of these are used for the standard 30 characters that are available on the keyboard. The two ramaining positions are taken by the SPACE character (10001) and the NULL character (00000), which is also known as STOP.
 
Block diagram
Although the circuit diagram of the M-125 is very complex, its operating principle is similar to, but more advanced than, the Enigma cipher that was used by the Third Reich during WWII. The extra complexity was added to circumvent certain cryptographic weaknesses of the Enigma.

Block diagram of the German Enigma machine

Let us first consider the above block diagram of the Enigma. It has 26 keys that operate 26 switches. The current from the battery is passed by these keys through the plugboard (German: Steckerbrett) onto a static entry disc (German: Eintrittswalze, or ETW). From the ETW, the current is passed through the cipher wheels until it hits the reflector (German: Umkehrwalze, or UKW). The UKW returns the current back through the wheels, the ETW and the Steckerbrett, after which it arrives at the lamp panel where the lamp of the encoded letter lights up. This is the output.

Block diagram of the M-125

The operating principle of the M-125 is similar, but the plugboard has been replaced by a card reader that offers a stronger encryption by providing a non-self-reciproke permutation. The keyboard (at the right) is used for the input. It consists of 30 electrical contacts; one for each key. Furthermore, the keys are mechanically encoded into a 5-bit digital code (similar to Baudot). When typing, the current from the 30 contacts is passed to the card reader at the top right.

From the card reader, the current is passed via the static entry disc, through the 10 cipher wheels. After the current arrives at the reflector on the left, it is returned through the 10 wheels, the entry disc and the card reader, until it arrives at the 5-bit encoder (bottom right), where the 30 lines are converted into a 5-bit code (similar to, but different from Baudot) for the printer.

 Block diagram in more detail
 
Magic Circuit
The use of a reflector makes the machine symmetrical, which means that the same settings can be used for encoding and decoding. A major drawback however, is that a letter can never be encoded into itself. This was considered a serious weakness of the Enigma cipher machine.

In the Fialka, this is solved by adding a clever electronic circuit to the reflector, to ensure that a letter can be encoded into itself. This is done by taking 4 wires out of the reflector (i.e. two pairs). One of these wires is used as the 'letter-can-be-itself' signal and is sent back to the keyboard. The remaining three wires are combined into a binary rotator. In the German Fialka literature, this circuit is called Dreipunkschaltung (three-point circuit), but we have dubbed it 'Magic Circuit'.

Reversing the direction of the binary rotator by swapping two lines

The effect of the Magic Circuit is that each letter has a 1:30 chance of being encoded into any other letter, making the machine cryptographically stronger than the Enigma. A side-effect of the binary rotator however, is the the machine is no longer fully symmetrical. This is solved by adding a Mode Switch (coding/decoding) that simply swaps two of three lines of the binary rotator.

 More about the Magic Circuit
 
Keyboard
The keyboard is an extremely complex mechanical assembly. It consists of 30 keys divided over three rows. When pressing a key, a lever will actuate the corresponding contact in an array of 30 switches that is mounted behind the keyboard. It is illustrated in the drawing below. The contacts are arranged in the order of the Russian alphabet. An extra switch is added for the spacebar.

The contact array that is fitted behind the keyboard

Pressing a key also actuates one or more rods, five of which are mounted from right to left underneath the keyboard, where they drive five electrical switches. This way the rods mechanically convert a key (1 of 30) into a 5-bit digital code that can be used to drive the printer.
 
Interior
The interior of the M-125 can easily be accessed by loosening two large bolts in the top of the cover (for one the top lid should be opened), and a small screw at the front, just below the keyboard. After that, the cover can lifted upwards, revealing the complex interior. The images below should give a good impression of the various parts of this extemely well-built machine.

M-125 Fialka interior (without wheels) seen from the front left


M-125 Fialka interior (without wheels) seen from the rear right

The machine can roughly be divided into three sections: the keyboard at the front, the cipher wheels at the centre and the printer/puncher at the rear. The card reader is hidden underneath the cipher wheels and is accessible via a drawer at the left. Alhough the machine has a highly modular construction, the various parts are mechanically intertwined in several areas.
 
All parts are mounted to the base plate (i.e. the bottom shell of the machine), which acts as a reference for the mechanical adjustment of some parts. Some axles and pawls are permanently fitted to the base plate to act as a mechanical interface between certain parts of the machine.

The electrical timing of the machine is generated by an interruptor contact at the left side of the machine, close to the main spindle. This contact is actuated by a notched disc that is driven by the main motor axle. This pulse also acts as the STROBE for the digital 5-bit data output.
  
Another view of the printer/puncher

At the front of the machine is the keyboard, which has a complex mechanical structure of metal arms, pawls and rods underneath the keys. Each key actuates one of the contacts of an array of switches that is mounted behind the keyboard. The rods below the keys are also used to mechanically generate a 5-bit digital code. The code is converted into electrical signals by means of 5 switches that are mounted in a small metal enclosure to the left of the keyboard.
 
To the right of the keyboard is the tape reader that is mechanically coupled to the keyboard. It directly drives the 5 rods underneath the keyboard, in such a manner that it mimics the operation of the keyboard. This means that it drives the 30 individual key contacts as well as the 5-bit encoder to the left of the keyboard.

The tape reader is driven by an axle that is part of the base plate assembly. When the user presses the green START key (ПУСК), the tape reader is coupled to this axle and starts reading the paper tape that is inserted at the front.
  
Close-up of the tape reader mechanics

The tape runs until the user presses the STOP key (СТОП) or a NULL character is encountered on the tape (00000), at which point the tape reader will be decoupled from the driving axle. The alignment of the tape reader is extremely critical and many of the adjustment are sealed (yellow).
 
The center part of the machine is taken by the wheel stepping mechanism, which becomes visible after removing the drum (i.e. the spindle with the 10 cipher wheels). It consists of two sets of transport-combs: the upper one for the stepping of the odd cipher wheels and the lower one for the stepping of the even cipher wheels.

When the motor is running, this mechanism is at rest, but as soon as a key is pressed, it is mechanically coupled to the main driving axle, causing a single step of the wheels. After one full revolution of the axle, it is decoupled again.
  
Top view of the wheel transport mechanism

Wheels 2 and 9 are advanced on each key press. The short metal pins at the other rim of the wheels (sometimes referred to as the notches) control the stepping of the over-next wheel. The presence of a pin inhibits the stepping of the wheel two places further. In other words: wheel 2 controls the stepping of wheel 4, wheel 4 controls the stepping of wheel 6, and so on.
 
If a pin is absent on one wheel, the wheel two places further will also make a step when a key is pressed. Of the odd wheels, wheel 9 controls the stepping of wheel 7, wheel 7 controls the stepping of wheel 5, 5 controls 3 and so on.

The output of the machine is available in three different streams: as a punched paper tape, in printed form and as digital signals, all of which is controlled by the printer/puncher mechnism at the rear right. The printer is driven by the output of a diode matrix that converts the 30 output lines into a 5-bit digital data signal.
  
Close-up of the printer/puncher

The diode matrix itself is hidden in the bottom section of the machine, below the mechanical parts. The 5-bit data signal is used to drive 5 solenoids that are located in a metal enclosure at the back of the printer/puncher mechanism. The solenoids in turn drive the five punchers of the tape puncher and also control the point at which the hammer of the printer is released.
 
In addition to this, the output is also available electrically from the brown 10-pin socket at the right rear of the machine. This signal can be used to drive external telegraphic equipment directly. It can also be used for transmission by connecting the R-590A (Rus: Р-590А) interface.

When the machine was used in combination with the advanced Power Supply Unit (PSU), which was the case in Poland, this output is used to drive the Electronic Counter Measures that are present in the PSU. It prevents an eavesdropper from obtaining information by tapping the power line.
  
M-125 interior without wheels, seen from the rear right

The machine is mechanically driven by a 24V DC motor, which is located at the rear left of the machine. The image on the right shows the rear of the machine with the grey motor at the right.

When the machine is switched ON, the motor runs continuously until it is switched OFF again. If a machine hasn't been used for some time, it is possible that the grease has dried up, preventing the motor from starting. In such cases it might help to rotate the kurdled knob at the bottom centre in the direction of the arrow. Ensure that the machine is off when you do this.
 
Small screw at the front of the machine Large screw on top M-125 interior without wheels seen from the front left M-125 interior without wheels, seen from the rear right Interior seen from the rear left Interior seen from the front right Close-up of the printer/puncher Another view of the printer/puncher
Close-up of the clock pulse generator Close-up of the tape reader mechanics Another view of the tape reader mechanics Wheel transport mechanism Close-up of the wheel transport fingers Close-up of the printer Top view of the wheel transport mechanism Mechanical 5-bit encoder

 
Positions of the serial number
The serial number of the Fialka was printed on a small serial-number badge that was mounted at the front of the machine, just below the keyboard. Unfortunately, this badge has been removed from most machines as part of the demilitarization process. Nevertheless it is possible to retrieve the serial number of a machine, as it is engraved in a number of parts inside the machine as well. The following locations are known:
 
Dust cover Serial number plate at the front of the machine Serial number to the right of the entry disc On the hinge inside the top lid Below the keyboard At the rear of the printer mechanism On the motor mounting post Serial number of the paper tape feeder

 
Newer version
Approx. 10 years after the introduction of the M-125, the machine was succeeded by the more advanced M-125-3, which is built on the same mechanical base. The newer machine can easily be distinguised from the older M-125, as most of them (except for the Russian version) have square key tops, rather than rounded ones. Furthermore it has an extra MODE selector at the rear of the printer.

 More information about the newer M-125-3.

The older M-125 and the later M-125-3 side by side (Polish versions shown here)


 
References
  1. Jörg Drobick, Nutzung der Fialka M-125
    Website: Der SAS- und Chiffrierdienst (SCD). Retrieved May 2014.

  2. Paul Reuvers and Marc Simons, The Fialka M-125 Reference Manual
    Copyright 2005-2009. Version 2.0, June 2009. ISBN 978-90-79991-01-3.

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Crypto Museum. Created: Monday 12 May 2014. Last changed: Monday, 12 October 2015 - 14:31 CET.
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