1
$\begingroup$

After you set up all rotors, position and plugs in Enigma machine. If you don´t get the signal of one word or one sentence... your enigma settings are desynchronized. How you can recover from this situation? Do you need to wait until next day?

I imagine some radio guy in the middle of the battle and I find very difficult to keep track of every message.

$\endgroup$
  • 2
    $\begingroup$ … which is why Enigma wasn’t often used by “some radio guy in the middle of the battle”. They mostly used other ciphers – because an Enigma was not only expensive, but also pretty inconvenient to transport when bullets fly around your head. Besides that, capturing such an Enigma (incl. the codebooks) in the field would have had a major impact on security (as it happened when the Brits got their hands on an Enigma and related material after capturing a German sub.) $\endgroup$ – e-sushi Mar 14 '18 at 17:30
1
$\begingroup$

As long as the plaintext has some sort of recognizable structure, it wouldn't be that hard to identify where a letter has been omitted. Here's an example (generated using the default settings of this online Enigma simulator):

Plaintext:  THEQ UICK BROW NFOX JUMP SOVE RTHE LAZY DOG
Ciphertext: OPCI LLAZ FXLQ TDNL GGLE KDIZ OKQK GXIE ZKD

Suppose the 15th letter of the ciphertext (N) is omitted. This would result in the following decryption:

Ciphertext: OPCI LLAZ FXLQ TDLG GLEK DIZO KQKG XIEZ KD
Plaintext:  THEQ UICK BROW NFVH JAOW FSNA TPPT ESUW BM

Clearly there's something wrong after the word BROWN, so let's reset the machine to its initial settings and insert an additional X after this word in the ciphertext:

Ciphertext: OPCI LLAZ FXLQ TXDL GGLE KDIZ OKQK GXIE ZKD
Plaintext:  THEQ UICK BROW NHPX JUMP SOVE RTHE LAZY DOG

This is much better, but now we have the word HPX, which makes no sense. A consecutive run of unlikely characters suggests that we inserted the extra character in the wrong place.

Therefore, the F in the original plaintext was probably correct, and the middle word of the plaintext must be F.X (with the . representing a character that was lost in transmission). There aren't many words that fit this pattern, and it isn't hard to guess which one is correct.

Obviously this method would be harder to use if a message contains clusters of missed and/or incorrect characters. But in that case the wireless operator at the receiving end could just request a retransmission of the message. I don't see why they would have to wait 24 hours.

$\endgroup$
  • $\begingroup$ Well... I imagine that some crucial information should be deliver to all units in an area. At 9:00 AM they sent a message but two units didn't received it, then the critical information is sent at 10:00 AM. How can that two unit get the correct message if they don't know anything about the previous one? And what I say of 24 hours is because you can wait until next day set up in order to be in sync. $\endgroup$ – JDL Mar 14 '18 at 15:03
0
$\begingroup$

Remember that all text was sent in groups of four or five letters. That means that you have a clue that you missed something when you get a group with one letter less. This plus that the over all speed is predictable so you can get an idea of how much you missed even if it's a whole group due to fading signal. I have seen sheets where they have put _ to indicate missed characters, something like

OPCI LLAZ FXLQ TD__ __LE KDIZ OKQK GXIE ZKD

as long as you keep the overall number of letters you may loose some part of the clear text but once you figured out how many to add you at least get the rest and hopefully the part lost is not to important.

$\endgroup$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.