Codes and Ciphers - February 2012, All Stages

We're celebrating the centenary of Turing's birth with lots of engaging tasks on codes and ciphers, devised with the help of James Grime of the Enigma project. We hope they stimulate interest in this intriguing field.

Problems

problem icon

What Was in the Box?

Stage: 1 Challenge Level: Challenge Level:1

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?

problem icon

What's Happening?

Stage: 1 Challenge Level: Challenge Level:1

Shapes are added to other shapes. Can you see what is happening? What is the rule?

problem icon

What's in a Name?

Stage: 1 Challenge Level: Challenge Level:2 Challenge Level:2

Here's a very elementary code that requires young children to read a table, and look for similarities and differences.

problem icon

Unlocking the Case

Stage: 2 Challenge Level: Challenge Level:1

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?

problem icon

It's a Scrabble

Stage: 2 Challenge Level: Challenge Level:1

Letters have different values in Scrabble - how are they decided upon? And would the values be the same for other languages?

problem icon

Some Secret Codes

Stage: 2 Challenge Level: Challenge Level:3 Challenge Level:3 Challenge Level:3

Can you follow the rule to decode the messages?

problem icon

Substitution Cipher

Stage: 3 and 4 Challenge Level: Challenge Level:1

Find the frequency distribution for ordinary English, and use it to help you crack the code.

problem icon

The Best Card Trick?

Stage: 3 and 4 Challenge Level: Challenge Level:1

Time for a little mathemagic! Choose any five cards from a pack and show four of them to your partner. How can they work out the fifth?

problem icon

Transposition Cipher

Stage: 3 and 4 Challenge Level: Challenge Level:1

Can you work out what size grid you need to read our secret message?

problem icon

Secondary Cipher Challenge Part 1

Stage: 3 and 4 Challenge Level: Challenge Level:2 Challenge Level:2

Here is the start of a six-part challenge. Can you get to the end and crack the final message?

problem icon

Substitution Transposed

Stage: 3 and 4 Challenge Level: Challenge Level:3 Challenge Level:3 Challenge Level:3

Substitution and Transposition all in one! How fiendish can these codes get?

problem icon

Secret Transmissions

Stage: 4 Challenge Level: Challenge Level:2 Challenge Level:2

How can Agent X transmit data on a faulty line and be sure that her message will get through?

problem icon

More Secret Transmissions

Stage: 5 Challenge Level: Challenge Level:2 Challenge Level:2

In 'Secret Transmissions', Agent X could send four-digit codes error free. Can you devise an error-correcting system for codes with more than four digits?

problem icon

Probably a Code?

Stage: 5 Challenge Level: Challenge Level:3 Challenge Level:3 Challenge Level:3

Is the regularity shown in this encoded message noise or structure?

problem icon

Stage 5 Cipher Challenge

Stage: 5 Challenge Level: Challenge Level:3 Challenge Level:3 Challenge Level:3

Can you crack these very difficult challenge ciphers? How might you systematise the cracking of unknown ciphers?