A half term trip to Bletchley Park inspired the following activity …
Task 1
Go to
https://billtuttememorial.org.uk/codebreaking/teleprinter-code/
Read about teleprinter code and the rules of addition.
Task 2
In the alphabet in the link above, I and N are incorrect.
Can you use their addition table to work out what I and N should be? Remember that same symbols added make a dot, and different symbols make a cross.
Here is an addition table in alphabetical order.
Task 3
Code HELLO with the key ANQPC.
How would you get back to HELLO?
Solution here
Task 4
Read about the Tiltman break here
Task 5
Try it out for yourself!!
Above are two messages sent with the same key. One has been abbreviated after the operator was asked to send it again. Your crib is that it starts MESSAGE NUMBER (of course with a 9 in the middle!). You also know it is a weather report.
If you add together the two messages letter by letter (using the table) you will end up with the two messages added together, because for:
Message1 +key + Message2 + key
the keys will cancel out and it will be Message1 + Message2
So if you can guess it starts MESSAGE9NUMBER then you can add this to the sum of the two messages and as they start to be different you can work out each one …