Crack a code with a Crib
Spies like computer scientists because they help end wars!
In World War II, the Allies listened in to radio calls made by Hitler’s armed forces. His Generals thought no one could read their messages because they used secret codes. But the Allies cracked the codes, so knew what they were planning!
The Brits realised that it helped that the messages followed patterns. To work out the German’s day password, the British used cribs. These were common phrases that they could guess in a message.
They first had to find an encrypted version of a message where they already knew, or could guess, what it said. For example, they might look for a message that looked like an encrypted version of ‘I have nothing to report.’ (‘Keine besonderen Ereignisse’ in German).
The weather helped a lot. The word ‘weather’ (‘wetter’ in German) appeared in the same place in messages the Germans sent at the same time every day. Once the code crackers knew this they could use it to help them crack the code every day.
The fact that the Germans wrote ‘Heil Hitler’ all the time helped too! Hitler’s demand that he be glorified helped lose him the war!