Imagine you are a secret agent. You have listened in to two encrypted radio messages. Each letter of the alphabet is replaced by a number from a code wheel. To read the enemy’s orders, you must work out what code wheel they used.
MESSAGE GRID 1: ALL ABOUT WEATHER
MESSAGE GRID 2: THE PLANNED ATTACK
How? Use a crib!
The first message is a weather report. They always start with the word “WEATHER” followed by a space. That is the crib. Use it to work out the code wheel they used.
Look at Message Grid 1. W goes in the first box so W is number 3. Put W in position 3 of your code wheel too. E goes in the second space on the Message Grid. That is number 6, so put E on your code wheel against number 6. Do this with each letter in the crib, “WEATHER”. Don’t forget the space which is the last character in the crib. Draw a solid square to mean a space is there and then you can get to work on the rest of the message.
Use the code wheel to fill in the other letters everywhere you find their number in the Message Grid. Next, look at the message starting to form. Is it starting to make sense? If you can fill in any blanks to make a word, you can add the new letters back into the code wheel. Think of weather words, like SUN, WIND, SNOW. Do they fit in the message?
Once you have cracked the first message, work out what the second message says using your code wheel. Even a partial code wheel may be enough to crack the second message, and so know what the enemy is planning.
Fun to do! Create your own coded message
Can you create your own coded message: maybe about Armistice day or another important event in WWII that you know about?
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