Bob Lord's Crypto Museum
Reel 1
Reel 2
Reel 3
Reel 4
First screen:
War Department
Official Training Film
T.F. 11 – 1400
Army
Service Forces
Second screen:
Produced by
Army
Pictorial Service
Third screen:
Converter
M-209
[Reel 1]
One of our messages in the hands of the enemy may lose a battle, but if that message is cryptographed, the enemy will lose enough time figuring it out to make the information useless. To help you cryptograph more effectively, this converter, the M-209, has been put into use throughout out the Army. There are several models of the M-209; all operate the same way. To see how, let’s encipher the simple word “GO”.
Whenever you encipher, be certain that the encipher/decipher knob is at “C”. Set the letter “G” on the indicating disk, opposite the indicating index. Turn the drive knob as far as it will go. Set the letter “O” opposite the indicating index. And turn the drive knob once again. The result is the word “go” in cipher. Now let’s decipher it.
First, set the cipher/decipher knob to “D”. Next, reset the letter counter to zero. Set the letter “X” opposite the indicating index, then the letter “Z”. Here is what we get: our original word “GO”.
This system of cryptographing is known as “cipher substitution”, which simply means that different letters are substituted for the ones you set up. In this case, “X” was substituted for “G”, and “Z” for “O”. This substitution is brought about by the interaction between the lugs on these drub bars, and the pins on these key wheels. In order for your message to be deciphered, the pins and lugs of both your converter, and that of your receiving operator, must be set exactly alike. Charts are provided to tell you how to set them.
Assuming that this converter is already set according to a chart, let’s encipher this message. Set the cipher/decipher knob to “C”. Then set the letter counter to zero by pushing down the reset button and turning the reset knob until the counter clicks into position. In order to make the cryptogram difficult to break down, 6 revolving key wheels are used. The first step is to rearrange them in any order you desire. Do this with your thumb or fingers; a hard object like a screwdriver will mangle the letters and ruin the wheel grooves.
The 6 letters now lined up along this benchmark form what is known as the “external message indicator”. Since you have to refer to it later, this external message indicator is always written down. And here’s an important point: you use an external message indicator only once with in conjunction with a particular pin and lug setting. Now select at random any letter at random on the indicating disk. In this case, we’ll take “L”. Record it along with the external message indicator. Next encipher “L” 12 times. From these 12 letters we have to form still another 6 letter combination which will be the “internal message indicator”.
First reset the counter to zero. Then set the first letter “J” on the first keywheel. Set the second letter “W” on the second keywheel. But there is no “W”! A flaw in the machine? Not at all! Certain letters are deliberately omitted from the 2nd, 3rd, 4th, 5th, and 6th keywheels. Whenever one of the 12 enciphered letters can’t be found on the keywheel, it’s crossed out and the next letter used. Let’s try “U” for the 2nd keyweel. Yes! Since it’s here, we can use it.
Next is “P” which goes on the third keywheel. It too can be used. Now “D”. The next letter is “J”. Next is “R”. But “R” isn’t on the sixth keywheel. So we cross it out and try the next letter, “S”. No “S” either, so it too is crossed off. Now let’s try “G”. “G” is OK, so we’ll use it. We have now set up an internal message indicator from the twelve cipher letters. Since we have the keywheels lined up, we must destroy the twelve cipher letters for security sake.
[Reel 2]
All right! We’re now ready for the message. Set each letter on the indicating disk and encipher it. Notice that as each letter is enciphered, the letter counter is registered. This gives the operator a check on the letters he has already enciphered and is useful in locating errors. The next letter, “U”, is already in place on the indicating disk. In such a case, turn the disk in either direction to release the drive knob. Then set up the letter again, and continue enciphering the message.
At the end of each word, encipher the letter “Z”. Later when the message is deciphered, “Z” will come out as a blank space, separating the words. Where a single letter occurs, use the phonetic name. In this instance, “EZ” for “E”. This use of phonetic names for single letters helps to prevent errors in enciphering and deciphering and in transmitting.
Since there are no numbers on the indicating disk they must be spelled out. “T-W-O” for “2”, and so forth. When you are finished, roll out a few extra inches of tape before tearing it off. Here is the enciphered message. Notice that the last group contains only three letters. Since the M-209 enciphers in five letter groups, it is necessary to complete this group by writing in two “X”s.
Now we have to add three indicators that go before and after every M-209 cryptogram. The first indicator is obtained by repeating the letter we originally enciphered twelve times. The letter “L” in this case. This is known as the “system indicator”, and tells the receiving operator that the message was enciphered on the M-209. The second indicator is the “external message indicator”. The six letters we selected at random and set up on the key wheels before. Remember we wrote it down for later use. This is it. The third indicator is the “key list indicator” which tells the operator what chart to use for his pin and lug setting. OK, we have our three indicators, the repeated letter that tells us a converter was used, the six letters selected at random forming the external message indicator, and the key list indicator for the pin and lug setting. Notice that we separated the first three letters of our “external message indicator” from the last three, to get five letter groups. All we have to do now is to transfer the message onto the proper blank, and then dress it up with the necessary information for forwarding. Finally, always turn the key wheels so that the internal message indicator is broken up. The message may now be sent to its destination by any of the Army’s various forms of communication. Ours is going by radio.
Here it is arriving at another message center. Let’s see how it’s deciphered. The repeated letter “L” tells the operator that an M-209 converter was used. The key list indicator tells him what chart to use for the correct pin and lug setting. In this case, we’ll assume that the converted is already set according to the chart. To decipher the message, the operator starts by following the identical procedure used when enciphering. He sets the counter to zero, and the encipher/decipher knob to “C”. Next he picks out the external message indicator and sets his key wheels in accordance with it.
[Reel 3]
Now he takes the repeated letter “L” and enciphers it twelve times. From this, he obtains the same internal message indicator that the sending operator used. He zeroes the letter counter, then sets up each usable letter on the six key wheels. Since the letter “W” is missing from the second keywheel, he has to setup the next letter, “U”. The he continues with the remaining letters. Here’s the result: the original internal message indicator. Now he can start deciphering. First the encipher/decipher knob goes to the “D” position. Then beginning with the first letter after the indicator groups he sets each letter in position on the indicating disk and deciphers it. When deciphering, the spaces between the letter groups are disregarded. All the “X”es at the end of a message must be deciphered because the receiving operator doesn’t know if they have merely been written in or are an actual part of the cryptogram.
Here’s our original message. Let’s compare it with the cryptogram. It’s obvious that the last two X’s are meaningless so the operator crosses out the corresponding letters. The letter “Z” which we put in after each word in the original comes out as a blank thus spacing the word. Since it comes out as a blank, it must be filled in where it obviously belongs, as with the Z in “zero”.
The last step is to turn the key wheels to break up the internal message indicator, and to destroy all work copies of the code just as we did after enciphering. The message can now be transferred to a blank, dressed with the necessary information, and sent to the addressee.
Now that we have enciphered and deciphered a complete message, let’s go back and study in detail the pin and lug settings that are the key to the converter M-209. The pins for each letter on the 6 keywheels are movable. So are the lugs on the metal bars of the drum. The charts used to set up these pins and lugs are changed every day so whenever a message is either sent or received the charts must be checked for the proper pin and lug settings. These letters and dashes indicate the pin positions. A letter means that the pin goes to the right. A dash means that it goes to the left. Before making a setting, all pins must be moved to the left. Now that this is done, we can set them according to the chart. In the first column is a dash, therefore the pin of letter “A” goes to the left. But this pin is already on the left so you don’t need to touch it. Letter “B” means the pin of letter “B” on the first keywheel must be pushed to the right. The same with “C”, the pin goes to the right. Be sure that each pin is pushed all the way so that it is flush with the side of the keywheel. An improperly set pin may slide into the wrong position and cause an error.
Another dash. You don’t have to move “D” pin since it’s already to the left. Continue this way until all the pin positions indicated on the chart have been set on all the key wheels. Now you are ready to tackle the problem of setting the lugs.
These numbers on left of the chart, one through twenty-seven, represent the 27 drum bars. While these numbers here correspond to the numbers on the number plate. For drumbar number 1, the lug positions are for 3 and 4. Therefore on bar number one the lefthand lug is moved into position 3. The righthand lug is set in position 4. Be sure each lug catches firmly in its correct position. For drumbar number 2, the lug positions are 0 and 4. Therefore on bar number 2, the lefthand lug is moved into the zero position, and the righthand lug is moved into position 4. And so on until all the lugs are set.
To make sure all lugs and pins are correctly placed, you check against this group of letters at the bottom of the lug chart. It’s called the 26 letter check. Here’s how it’s done. Set the counter to zero, and the encipher/decipher knob to “C”. Then turn all 6 keywheels to “A”. Now encipher 26 A’s one after another. The result should match exactly the 26 letter check. If it doesn’t, a lug or ping has been incorrectly placed and the positions must be rechecked against the chart. In this case, the letters check and the converter is ready for enciphering or deciphering.
[Reel 4]
Now a few special points. First the jamming of the machine. When the drive knob hasn’t been turned completely, the indicating disk won’t move. Complete the turn and the disk is free. Next, in resetting the number counter, be sure the reset knob snaps firmly into place so that all the zeros are exactly in line. Otherwise jamming occurs. The machine will also jam if a pin or lug is partly out of position. Then the converter must be checked thoroughly until the faulty adjustment is found and corrected.
To put in a new roll of tape, release the cover and tilt it back. Then release the guard and pull it forward. Place the roll so that it will unwind counterclockwise. Thread the tape through the tape slot and feed the end through the tape channel under the roller. Several turns of the feed knob will bring the tape into position.
To replace the ink pad, push the spring arm to one side and remove the pad with the tweezers. Be sure not to open the fresh inkpad container over the converter. The ink may spill or the pad itself may fall into the mechanism. Push the spring arm to the side, and slip the new pad into position. Both ends of the inkpad may be used so when one end becomes dry, the pad is simply reset in the reverse position.
About every 250 operating hours the converter must be oiled. Again, don’t open the oil container over the converter. An excess of oil may gum up the works.
To clean the typewheel, use type cleaner with the brush, turning the disk until all the dirt is removed.
Some models of the M-209 have plastic parts which should never be cleaned with chemicals. For example, this wheel. Use only a dry brush for cleaning such models.
This reproducing disk shows exactly that letter which appears on the tape each time a letter is enciphered. Should an operator run out of ink or tape he can still cryptograph a message by recording the letters off this disk.
Finally, if you’re in immediate danger of capture, burn the signal operation instructions page by page. Then set all the pins to the left, and all the lugs to zero. When this is done, destroy the machine with an ax, or any other handy object. Rifle fire or a grenade will also do an effective job of destruction.
Now let’s have a quick review of the whole procedure of enciphering and deciphering. Assume the pins and lugs are set and checked according to the chart. The encipher/decipher knob is set to “C”, the letter counter at zero. Set up your external message indicator. Six letters selected at random that don’t spell an actual word, and record them. Next, choose any letter. Record it, then encipher it 12 times. Select the internal message indicator from these 12 letters. Then encipher the message. Remember that phonetic names are used for single letters, but numbers must be spelled out. And that the letter “Z” must be enciphered between words for spacing. When necessary, add X’s to complete the last 5 letter group. Now in the same order before and after the text, write the system indicator, the external message indicator, and the key list indicator.
Finally, transfer the message to a form and complete it. When you decipher a message, you begin by following the identical procedure used when enciphering. The repeated letter informs you that the message was enciphered by an M-209. And the key list indicator tells you what pin and lug setting has been used. In this case it’s the one already on the machine, so you’re ready to begin. First set the counter to zero. Next, look for the external message indicator and set the key wheels in accordance with it. With the encipher/decipher knob at “C”, encipher the repeated letter 12 times. After this is completed set the counter to zero again. Select the internal message indicator from the 12 letters. Turn the encipher/decipher knob to “D”, and decipher each of the letters in the cryptogram including any X’s at the tail end. Roll out sufficient tape before tearing so as not to lose any of the message. “Z” deciphers as a blank space, so fill it in where necessary. Transfer the deciphered message to a message blank, address it, and then forward. And finally, break up the internal message indicator after each message is cryptographed. And destroy all work copies of the work tape.
Converters are used under various conditions, at higher headquarters, in foxholes, in the open. Some of the conditions don’t include tables or shelves. At such times, the operator can attach the converter to his leg by means of the carrying strap, and have both hands free to operate. When not in use, the converter is always kept in its canvas case to protect it from dirt and dampness. The converter is a valuable piece of equipment, but it’s still equipment. In order to perform its job of confusing and delaying the enemy, it has to be carefully protected and properly operated. That’s up to you.