AHC: Lorrenz cipher still unbreakable

[Myrtonos]

Another rotor machine encryption machine used during WWII, by the German High Command, was the Lorenz machine. It used a more elaborate Cipher, and doubled as a teleprinter, enciphering and deciphering text automatically, so that those operating it never read or wrote the ciphertext.
By the way, characters in the plaintext were encrypted using 5 bit symbols, which does allow for more possible symbols then there are letters in the alphabet.
What if the German operator, sending a message from Athens to Vienna did not need to resend it, or used a different starting position the second time?

 

[Deleted member 1487]

https://en.wikipedia.org/wiki/Lorenz_cipher

The deciphered Lorenz messages made one of the most significant contributions to British Ultra military intelligence and to Allied victory in Europe, due to the high-level strategic nature of the information that was gained from Lorenz decrypts.[6]

https://en.wikipedia.org/wiki/Cryptanalysis_of_the_Lorenz_cipher
You forgot to include why it was so important. Effectively it allowed the Allies to read all of Germany's high level communications between Hitler and the army command in the field. Historically there were several upgrades to the system during the war to improve it's security, but the Brits had already reverse engineered the machine just from figuring out the logical way it encoded, so were able to keep up with the new cipher versions. If the Germans never make the mistake that allows the break in of their code or switches to a new machine (there apparently was another one that was never broken, but was never widely used), then the Allies are cut out of Germany's strategic decision making, which doesn't let them know if their deception operations have worked or any other number of forewarnings of German intentions in the war. As a result the Allies are more cautious and perhaps get surprised more, but perhaps they focus more on other means of intelligence and are mostly able to overcome the lack of access to Lorenz.

 

[Nik]

The problems, IIRC, with the extended version --More rotors etc-- were the increased set-up time and distributing the set-up code books. Part of its security was obscurity. With many, many more sets 'in the field', there would be a lot more data to work from...

Wasn't the naval variant broken because u-boats returned weather reports in a standard format ??

 

[Myrtonos]

But weren't those weather reports in the enigma code? The rigid pattern of many enigma messages made it easy to break at Bletchley park.

I don't know whether the German High Command encrypted everything with Lorenz or only certain messages. Did they encrypt things such as 'season's greetings' every Christmas, and other messages conformed to a rigid structure?

 

[MattII]

Wasn't the naval variant broken because u-boats returned weather reports in a standard format ??

Actually, a big help there was the repeated use of the word 'eins' ('one'), that gave the British something of a baseline to work from.

 

[Myrtonos]

Other words repeated were wetterbericht (weather report). If encrypted messages are returned in a standard format, then it is quite possible to use context to help break the code.

The point is that a mistake made by a high command officer while resending a message allowed the code to be cracked. What if either the officer either didn't need to resend or used a different key the second time?

 

[Myrtonos]

So can anyone imagine history where that high command officer didn't have to resend the message, or resend it with a different key.

 

[Myrtonos]

If the Germans never make the mistake that allows the break in of their code or switches to a new machine (there apparently was another one that was never broken, but was never widely used), then the Allies are cut out of Germany's strategic decision making, which doesn't let them know if their deception operations have worked or any other number of forewarnings of German intentions in the war. As a result the Allies are more cautious and perhaps get surprised more, but perhaps they focus more on other means of intelligence and are mostly able to overcome the lack of access to Lorenz.

And the second world war would have gone on for longer.