Kjartan Poskitt - Codes: How to Make Them and Break Them!

First Racehorse for Young Readers edition 2017

All rights to any and all materials in copyright owned by the publisher are strictly reserved by the publisher.

First Published in 2007 by Scholastic Ltd, UK

Cover design 2017 by Racehorse Publishing

Text Copyright Kjartan Poskitt, 2007

Illustrations Copyright Ian Baker, 2007

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Cover design by Michael Short

Cover illustration by Ian Baker

Print ISBN: 978-1-63158-127-4

eBook ISBN: 978-1-63158-128-1

Printed in the United States of America

To my lovely boss Miss Lisa Edwards with thanks for sparing the time to make a guest star appearance in the last pages of this book.

CONTENTS

A SNEAKY START

As you launch yourself into this extraordinary book, notice that arranged within the main text there are many cunningly concealed kinds of trick messages, only you dont see any just yet.

Hah! Did you spot it? No? We hate to tell you this but you have already read a secret message. Yes indeed, a hidden announcement of national importance was sneaked into that first sentence! It uses one of the easiest sorts of codes, but dont worry if you didnt see it as well explain it soon.

There are hundreds of different ways you can send a message so that it can only be read by the right person, and nearly all of them rely on math. Some codes need extremely murderous math and well have a look at those later on, but the code in the first paragraph used some of the simplest math there is. If you want to decode the message, all you need to do is count to 2 but it still fooled you, didnt it?

There are three basic ways of sending secret messages:

SCRAMBLED (where the order of the letters is mixed up)

SUBSTITUTED (where each letter is swapped for something else)

DISGUISED

By now you might have realized that the message in the first sentence is disguised. This means that when you read the sentence, you didnt even realize there was a message there! If wed started the book by saying XQ3JJF8MZ27 then you might have got a bit suspicious, but as it was, you didnt know there was anything strange happening until we told you.

Its time you found out how to decode the first sentence, but do bear in mind that when you see what it says, you neednt worry. Its not as scary as it seems and all is in hand (we hope). Heres that sentence again, but youll notice that the words are now split into groups of two.

As you launch yourself into this extraordinary book notice that arranged within the main text there are many cunningly concealed kinds of trick messages only you dont see any just yet.

Now just look at the first letter of each group. Got the message?

Eeek! Its the evil Gollarks from the planet Zog, but dont panic. Just dive behind the sofa, grab the TV remote and prepare to zap anything green and slimy that approaches. The odd thing about Gollarks is that although they like to invade, causing mayhem and destruction, all it takes is one little push of the TV remote control and ping they end up doing whatever program you switched to. Today its Gorgeous Gardens.

Special words to know

The difference between the KEY and the ALGORITHM

The algorithm for the first sentence of this book (the one that was coded) is that the hidden message is made up from the first letters of some of the words. Even if the crackers know the algorithm, they dont know which words in the sentence are the important ones.

The key describes exactly which words were important. For instance it could be every fourth word, or every fifth word, or perhaps every word before a comma. Crackers who know the algorithm can experiment and try to find the key, and for our first sentence its so simple they might get it quite quickly.