Now that you know a little about codes and ciphers, let's try to make our own. Say we'd like to send the following message:

I want pizza for supper.

We'll start with a simple substitution cipher, where A stands for Z and vice-versa, B stands for Y, C for X, and so on. Therefore, our message will now read like this:

R dzmg kraaz uli hfkkvi.

That's pretty scrambled. But someone who knows what they're doing can break that pretty easily, especially if our message was longer. So, let's make it a little more complicated by reversing the whole thing:

.ivkkfh ilu zaark gmzd R

Not bad, but anyone who knows the basics of English grammar will be able to figure out that we reversed our message just by noticing that we start with a period and end with a capital letter. So, let's eliminate punctuation and capitals:

ivkkfh ilu zaark gmzd r

We're getting there, but we've left a clue that could help someone break the message. Since "A" and "I" are the only letters that can be used as entire words, the letter "r" sitting all by itself there at the end must actually represent one of those two letters. While not particularly useful on a message this short, a longer message with more "r's" in it would be easy to decipher with this clue. So let's run everything together into one long string:

ivkkfhiluzaarkgmzdr

There--that's not world-class, but it should stump your friends for awhile! To decipher your encoded message, all you have to do is reverse it and substitute the encoded letters for the correct ones. This will give you "iwantpizzaforsupper," which is easily recognized.

Now that you know a little bit about codes and ciphers, see if you can come up with your own! Just remember that your messages should be as easy as possible to decipher for someone who knows the key; in other words, don't make it so complicated that it takes a long time to read your own messages!

Modern ciphers use mathematical formulas called algorithms to encrypt messages. Most of these ciphers are impossible to crack (or even read) without a special computer program, and computers must be used to encrypt the message. These types of ciphers are very difficult to crack even if someone knows exactly how they work, as long as the key is kept a secret. This is a little hard to explain, so let's use a little project as an example. I'll give the instructions first, then get back to the computerized ciphers afterwards.

An early encoding method used a device called a scytale (rhymes with "Italy"), which you can easily make yourself. You'll need two or three rods or dowels of different diameters, a pen, and some long strips of paper about half an inch wide. Choose a dowel and start wrapping the paper around it as shown in the diagram. You may want to tape the ends in place.

Now, write a message on the paper, lengthwise along the dowel, one letter for each turn of the paper. When you get to the right-hand end of the dowel, go back to the left end and start a new row of letters. When you're finished writing your message, unwind the paper and you'll have a random-looking sequence of letters that won't make any sense at all. The message can only be read by wrapping the paper around the right size of dowel. Take turns writing scytale messages with different sizes of dowels and decoding them!

Now, think about a computerized cipher again. Someone can know exactly how the cipher works, yet still be unable to crack a message because they don't have the key. A scytale works the same way, since an enemy could know exactly how to read the message (wrap the paper around a rod), but without the key (a rod of the correct diameter), he still could not read the message. Modern computerized ciphers work on more or less the same principle.

I hope you've enjoyed this brief foray into the exciting world of codes and ciphers! tnU nli txe mit h,e ppa icy ehp nir !g

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Matthew Lewis, a homeschool graduate, is the web developer, and occasional columnist, for Home School Enrichment Magazine. Matthew is a self-described computer geek who enjoys doing things during his free time which he says would sound much too boring to be mentioned here.

This article was originally published in the Sep/Oct '07 issue of Home School Enrichment Magazine. For more details, visit http://HomeSchoolEnrichment.com