What would have happened if the enigma had not been deciphered?
Answer from: Daria Semenova:
GP. General practitioner. Graduated from the First Moscow State University...
Enigma was destined to be deciphered. The Germans left a pretty big security hole: in the Enigma (the German version, since the British later corrected this in their version of the machine) every letter could not be encrypted into itself ("а" could be any letter but a "а"). This reduced the number of choices required to some finite number of. In addition, every morning the Germans broadcast a certain standard message, the contents of which the British were well aware of. Bottom line, the enigma's been cracked.
Except they couldn't let the Germans find out about it. Otherwise the Germans would have changed the encryption and all the effort would have been wasted. So a lot of the attacks that the British knew about had to be "missed", because the British could only find out about them from the Nazis' conversations.
If the Enigma had not been deciphered, the war might have dragged on, there might have been more casualties. The Allies, after all, would have had a harder time finding out the Germans' plans and dispositions. But no more than that.