Here's a very elementary code that requires young children to read a table, and look for similarities and differences.
A case is found with a combination lock. There is one clue about the number needed to open the case. Can you find the number and open the case?
This big box adds something to any number that goes into it. If you know the numbers that come out, what addition might be going on in the box?
Shapes are added to other shapes. Can you see what is happening? What is the rule?
Can you follow the rule to decode the messages?
I was looking at the number plate of a car parked outside. Using my special code S208VBJ adds to 65. Can you crack my code and use it to find out what both of these number plates add up to?
Jenny Murray describes how she developed her interest in making and breaking codes.
This article describes the underlying mathematical ideas and skills involved in the important mathematical application of coding.
Simon Singh describes PKC, its origins, and why the science of code making and breaking is such a secret occupation.
The Enigma Project's James Grime has created a video code challenge. Watch it here!