# Codes and Ciphers - February 2012, Stage 2&3

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

### Unlocking the Case

##### Stage: 2 Challenge Level:

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?

### It's a Scrabble

##### Stage: 2 Challenge Level:

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

### Some Secret Codes

##### Stage: 2 Challenge Level:

Can you follow the rule to decode the messages?

### Substitution Cipher

##### Stage: 3 Challenge Level:

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

### The Best Card Trick?

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

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?

### Transposition Cipher

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

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

### Secondary Cipher Challenge Part 1

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

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

### Substitution Transposed

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

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