33
edits
Changes
Jump to navigation
Jump to search
mLine 56:
Line 56: − +
→The 4th Rotor
=== The 4<sup>th</sup> Rotor ===
=== The 4<sup>th</sup> Rotor ===
Later in the war, the Nazis inceased security by upgrading the machines to use a 4<sup>th</sup> rotor, but they committed an incredible blunder. It took some time to equip the entire fleet with the new machines, since individual submarines had to be given one the next time they were in port. During this transition period, the operational instructions were for those sumarines with the new machine to leave the 4<sup>th</sup> rotor in position zero. This made it compatible with the older 3-rotor machines. On one occasion, a submarine sent a message with the 4<sup>th</sup> rotor in a non-zero position. When the operator realized the mistake, he set the rotor back to zero and ''sent the exact same message again''.
Later in the war, the Nazis inceased security by upgrading the machines to use a 4<sup>th</sup> rotor, but they committed an incredible blunder. It took some time to equip the entire fleet with the new machines, since individual submarines had to be given one the next time they were in port. During this transition period, the operational instructions were for those sumarines with the new machine to leave the 4<sup>th</sup> rotor in position zero. This made it compatible with the older 3-rotor machines. On one occasion, a submarine operator accidentally sent a message with the 4<sup>th</sup> rotor in a non-zero position. When the he realized the mistake, he set the rotor back to zero and ''sent the exact same message again''.
The British knew that a 4<sup>th</sup> rotor was coming, but did not know how it was wired. This would have been an extremely serious problem, and might have shut down their decryption efforts for some time. But, when they were engaged in their routine breaking of that day's traffic, they noticed that a message was gibberish. They also noticed that it was of exactly the same length as the following message. They correctly guessed what had happened, and, by comparing the messages, were able to deduce how the 4<sup>th</sup> rotor was wired.
The British knew that a 4<sup>th</sup> rotor was coming, but did not know how it was wired. This would have been an extremely serious problem, and might have shut down their decryption efforts for some time. But, when they were engaged in their routine breaking of that day's traffic, they noticed that a message was gibberish. They also noticed that it was of exactly the same length as the following message. They correctly guessed what had happened, and, by comparing the messages, were able to deduce how the 4<sup>th</sup> rotor was wired.