Introduction

Cryptography is the science of encoding and decoding secret messages.

Julius Caesar used codes to send secret messages, as did Mary, Queen of Scots in the sixteenth century. She sent coded messages to her supporters who were plotting to murder the English queen, Elizabeth I. Elizabeth’s spymaster, Sir Francis Walsingham, intercepted the messages, deciphered them and discovered the plot.

During World War Two, the Germans used a code machine called Enigma that created codes that were so difficult to break that German submarines were able to sink British and American ships before they could be stopped. The British and Americans worked hard to break the codes for the Enigma machines, which was made more difficult when a machine with four rotors replaced that made with three. A breakthrough came when the codebooks, which told operators what settings to use on a particular day, were acquired by the Allies. 

Since World War Two, very sophisticated codes have been used to pass secret messages around the world. Groups such as MI5, the FBI, and the CIA spend millions of pounds and dollars on developing new codes and breaking the world’s most difficult codes. The technology that has been developed as a result has been used in computer technology, and the QR Codes that you can use if you have a smart phone have been created as a result.

(With thanks to Thomas Briggs, Education Officer at Bletchley Park for his advice on the Enigma machine and codebooks)

Challenge

Battleships is a codebreaking game.

You are going to play a game of Battleships with a difference. You have the chance to break a code that has been set for you.

Command has received intelligence of the locations of enemy ships, but they are encoded. You must decode the location of the enemy ships and sink them. 

The Rules:

Three enemy ships are located somewhere in this sector.

 

	A	B	C	D	E	F	G
1
2
3
4
5
6
7

 

The enemy has used two different codes to hide their ships. To find the locations of the enemy ships, you must crack both codes. You have the following information:

Letter in code

A

B

C

D

E

F

G

H

I

J

K

L

M

Really means

Z

Y

X

Letter in code

N

O

P

Q

R

S

T

U

V

W

X

Y

Z

Really means

C

B

A

 

Number in code	2	4	6	8	10	12	14
Really means	1	2

 

Cracking these codes will enable you to locate the enemy’s ships.

Encoded Locations:

Ship 1: (Z1, Z2, Z3)

Ship 2: (T4, T5, T6)

Ship 3: (Y5, X5, W5)

Two Player Game:

 

Using the worksheets , you each need to decide where you would like to place your ships.

You are allowed three ships, each one taking up three squares on the grid. Ships must be placed vertically or horiziontally and cannot overlap.

You need to come up with a code for the location of your ships, and give the encoded locations to your opponent.

You must then take it in turns to fire at each other’s ships by guessing at the locations of them.

See if you can find your opponent’s ships before they find yours!

 

Further Reading

In this activity you have had a go at breaking some simple codes. If you would like to have a go at creating your own codes, why not try these.

Book Code:

Get two books that are the same, one for you and one for the person you want to send a message to. Find the words that you want to put into your message. For example, if you want to put the word ‘code’ into your message, and this word is on page 212 of the book, write down 212. Then, work out which line it is on and write this down. So, if the word ‘code’ is on line 7, you get 212-7. Then add the number of the word in that line. So if ‘code’ is the fourth word of that line, your code then becomes 212-7-4. Do this for all the words of your message. Only someone with the exact back you used, and who knows what the code means, will be able to read what you have written.

Caesar Cipher:

This is a bit like the letters code you had to break in the challenge, only the letters of the alphabet have been shifted three places backwards:

 

Letter in code

X

Y

Z

A

B

C

D

E

F

G

H

I

J

Really means

A

B

C

D

E

F

G

H

I

J

K

L

M

Letter in code

K

L

M

N

O

P

Q

R

S

T

U

V

W

Really means

N

O

P

Q

R

S

T

U

V

W

X

Y

Z

You can also go to the CIA website and see if you can beat their codebreakers!

If you want to read more about codes and codebreaking, why not start with Robert Churchhouse's Codes and Ciphers: Julius Caesar, the Enigma, and the Internet (2001), or Fred Piper's Cryptography: A Very Short Introduction (2002). 

The Black Chamber website has more information about codes and codebreaking.

You can find out more about the codebreaking that took place during World War 2 on the Bletchley Park website . 

For further information on studying History at the University of Manchester, you can visit the department's webpage . 

Bright Knowledge  (part of the Brightside Trust) can tell you more about what it's like to study History and what careers historians can go in to.