Secret activities to do at home

Crackers

Spies would use codes to pass secret messages to each other. If the

enemy captured these codes they would not be able to read the

message, unless they deciphered the code. Number substitution

codes were sometimes used by the S.O.E (Special Operations

Executive) during the Second World War. The 26 letters of the

alphabet would be represented by a number.

To get you started – what code words are these?

8. 5. 12. 12. 15 23.8.1.20 9.19 25.15.21.18 14.1.13.5

Send some secret messages to your friends or family using the

code!

Caesar Cipher

The Caesar Cipher is an alphabetic shift cipher. It was used by the

Julius Caesar to communicate with his generals. The code is a shift

of three letters down the alphabet. To decode a message shift the

letters backwards three letters. The table below shows this shift.

1 is the plaintext alphabet and 2 is the encoded alphabet.

Using this table you substitute the letters of the plaintext alphabet

(1) with the letter of the encoded alphabet below it (2).

For example:

THE HIDDEN SUPPLIES ARE IN THE HOLLOW TREE

Each letter is substituted so that the coded message is:

WKH KLGGHQ VXSSOLHV DUH LQ WKH KROORZ WUHH

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A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26

1 A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

2 D E F G H I J K L M N O P Q R S T U V W X Y Z A B C

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Now try encoding this message:

THE WHITE RABBIT HAS RETURNED TO THE HUTCH

To decode a message, do the opposite, looking up the encoded

letter (2) to find what the plaintext letter is.

Try decoding this message: LV WKLV GLIILFXOW ??

The Code Wheel

The Code Wheel is a type of Caesar cipher. It is also known as the

Alberti Cipher Disc.

It can be made out of paper, wood, or other materials. The Code

Wheel has two discs with the alphabet written once on both. One is

slightly larger than the other and sits on top of it.

To make your own code wheel, find two pieces of card. Using a

compass (or draw around plates etc.) cut one circle slightly larger

than the other. On each circle draw a slightly smaller circle and then

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1 A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

2 Z Y X W V U T S R Q P O N M L K J I H G F E D C B A

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mark off 26 equal sections for your alphabet. Do this on both. Then

fix the circles in the centre with a split pin or similar. You should be

able to rotate one circle around the other one.

The inner wheel is the plaintext alphabet, while the outer wheel is the

encoded alphabet. To be able to encode and decode messages, both

the sender and receiver need to know which letters will line up to be

able to read the message properly.

For example, if it was decided that plaintext A equals encoded X (A=X),

the Code Wheel would be rotated so that A and X line up at the start.

Then the message is encoded and sent to the recipient, who would

also line up their Code Wheel so that A matched X, and decode the

message.

Try sending some secret messages to your friends or family.

Abtash

Atbash is a letter substitution cipher. Instead of shifting along

the alphabet, the encoded alphabet is reversed. 1 is the plaintext

alphabet, 2 is the encoded alphabet.

When encoding, spell out your message using the plaintext

alphabet, but substitute with the corresponding letter in the

encoded alphabet below it.

The message SEND SUPPLIES TO HOUSE becomes HVMW

HFKKORVH GL SLFHV

There are lots of other ciphers. Why not invent your own code

and send secret messages to your family or friends to see if

they can decipher them.

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Innocent letter

The Innocent Letter was used by POWs (Prisoners Of War) more

often than spies, since it took a long time to write a really innocent

looking coded letter. Spies did not have the time to do this when

they needed to send an urgent message, but POWs had a lot of time

to think out a good coded letter. They could ask for escape supplies

to be sent or to send important information about the enemy back

to Headquarters. The sender and recipient need to have a pre-

arranged system to pick out certain words or letters to spell out a

secret message.

One such system is the use of the word after any punctuation.

One man in the Second World War was known for having terrible

punctuation and told his wife that if she ever got a letter from him

that used punctuation, to read the word after the punctuation and

that would reveal a code word.

He was captured and sent a letter using punctuation, and she was

able to decipher the code to send help.

Can you decipher this innocent letter by reading the word after each

punctuation mark to see the coded message?

Dear Mother,We are all fine. Wish you could see the old house now that it is owned by new people. You would be pleased that they have kept it so well. Would you like a drawing of the changes they’ve made to it? Send one I will, the next time I write to you. Boxes are stacked by the door but they are neat and tidy. Today I will sketch it and send it along.

Your son, Fred

What is the secret coded message?

A ● ▬ U ● ● ▬ B ▬ ● ● ● V ● ● ● ▬ C ▬ ● ▬ ● W ● ▬ ▬ D ▬ ● ● X ▬ ● ● ▬ E ● Y ▬ ● ▬ ▬ F ● ● ▬ ● Z ▬ ▬ ● ● G ▬ ▬ ● H ● ● ● ● I ● ● J ● ▬ ▬ ▬ K ▬ ● ▬ 1 ● ▬ ▬ ▬ ▬ L ● ▬ ● ● 2 ● ● ▬ ▬ ▬ M ▬ ▬ 3 ● ● ● ▬ ▬ N ▬ ● 4 ● ● ● ● ▬ O ▬ ▬ ▬ 5 ● ● ● ● ● P ● ▬ ▬ ● 6 ▬ ● ● ● ● Q ▬ ▬ ● ▬ 7 ▬ ▬ ● ● ● R ● ▬ ● 8 ▬ ▬ ▬ ● ● S ● ● ● 9 ▬ ▬ ▬ ▬ ● T ▬ 0 ▬ ▬ ▬ ▬ ▬

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International Morse Code

Morse Code was invented in 1836 by the American artist Samuel F.B.

Morse, the American physicist Joseph Henry and Alfred Vail. They

developed an electrical telegraph system that sent pulses of electric

current along wires which controlled an electromagnet at the

receiving end. However, a code was needed to interpret pulses into

letters in order to make sense of them.

Two different pulse lengths called dot (dit) and dash (dah) in

different combinations make up the alphabet. Additional

combinations are used for numbers and punctuation.

International Morse Code

1. The length of a dot is one unit.

2. A dash is three units.

3. The space between parts of the same letter is one unit.

4. The space between letters is three units.

5. The space between words is seven units.

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A ● ▬ U ● ● ▬ B ▬ ● ● ● V ● ● ● ▬ C ▬ ● ▬ ● W ● ▬ ▬ D ▬ ● ● X ▬ ● ● ▬ E ● Y ▬ ● ▬ ▬ F ● ● ▬ ● Z ▬ ▬ ● ● G ▬ ▬ ● H ● ● ● ● I ● ● J ● ▬ ▬ ▬ K ▬ ● ▬ 1 ● ▬ ▬ ▬ ▬ L ● ▬ ● ● 2 ● ● ▬ ▬ ▬ M ▬ ▬ 3 ● ● ● ▬ ▬ N ▬ ● 4 ● ● ● ● ▬ O ▬ ▬ ▬ 5 ● ● ● ● ● P ● ▬ ▬ ● 6 ▬ ● ● ● ● Q ▬ ▬ ● ▬ 7 ▬ ▬ ● ● ● R ● ▬ ● 8 ▬ ▬ ▬ ● ● S ● ● ● 9 ▬ ▬ ▬ ▬ ● T ▬ 0 ▬ ▬ ▬ ▬ ▬

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Unless you happen to have a handy Morse Code tapper at

home we suggest you either use a torch to send your messages

(leaving the light on a shorter time for the dit and longer for

the dah) or use your hands. You could make you left hand

the dot hand and your right hand the dash hand. Spread your

fingers and close again for each separate letter. Or you could

drive everyone mad and use the doorbell or whistle a different

length for each dot and dash.

Invisible ink

You can make your own invisible ink from onion juice, vinegar, apple

juice or lemon juice.

• Find a piece of paper and a paintbrush and squeeze some juice into a

cup (or a cotton bud works well as a disposable paintbrush).

• Write a message on the paper using the juice as ink. Let it dry.

• Write a different message on the paper using pencil or pen.

• To reveal the invisible ink message hold the paper over a light bulb or

carefully hold it in front of a candle ensuring you do not set light to the

paper. Make sure you do this with an adult present. Or sandwich your

paper between two pieces of greaseproof paper and ask an adult to iron

it for you for about two minutes. Or you can pop the piece of paper into

a medium to hot oven but check every few minutes before it burns. The

juice is acidic and weakens the paper and when heated discolours it and

reveals the message.

Design some secret gadgets

During the Second World War secret agents worked for an

organisation known as the S.O.E (Special Operations Executive). The

S.O.E spies flew from Britain to work undercover in occupied Europe.

They gathered information about the enemy and passed it back to

the British government. They were also involved in covert sabotage

missions like blowing up bridges.

These S.O.E agents had secret gadgets to help them.

Some examples were:

• Prunes sent as gifts to prisoners which had escape materials and maps

hidden inside.

• Hand grenades disguised like torches.

• Pens that could send out a jet of tear gas.

• Exploding oil cans, rats, potatoes, apples and dung.

• Maps printed on to silk scarves and then sewn into jackets.

• Magnetised trouser buttons used as a compass.

• Brushes, coins, pens and other everyday objects with hidden

compartments.

Have a go designing some secret gadgets that you think would be

useful for a spy.

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