Commercial Enigma cipher machine (Model D)
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The 1st Problem

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This problem is not difficult but you have to make your own
simulator. A good advice: read the hint accompanying the 
problem. 

The 2nd problem

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We know the beginning of the message. It is possible to use 
a manual method: “La méthode des batons” (rod method). If we 
use a computer program, the problem is very simple: we try 
all rotors starting positions (all message keys). 

The 3rd Problem
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The problem is similar to the second problem but more complex.
We know neither the rotors order  nor the ringstellung. Whether 
manually or using a computer program, you have to do more tries.

The 4th Problem
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We know nothing. You have to test all possible keys. 
Fortunately the Commercial Enigma does not have a plugboard. 
Number of tries remains low. A manual method is possible but
requires a lot of tests.

The 5th Problem
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Almost all messages are "in depth". 
You can solve them with a computer but using a manual method 
is fun.

The 6th Problem
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You do not know the wiring of the rotors. This is the main 
difficulty. Fortunately most messages are in depth.
Manual method are possible (like Knox).