Cool Secret Codes For Kids: Substitution Codes

There’s no getting around it: secret codes are cool. Spies use them to protect secret messages and that is very cool. George Washington used secret codes during the Revolutionary War, and there is no doubt that a white-wig-wearing future President of the United States writing in secret code was mighty cool. I feel cool just writing about secret codes.

Spies and secret agents use codes for a clear purpose. They have information to protect, intelligence they don’t want to share with an enemy, or sometimes even the fate of a nation to safeguard. But those of you who are not yet spies or secret agents can use secret codes just for fun. And what is more fun than disguising a message in a secret code that only you and a trusted friend (or perhaps a fellow agent) can understand? That’s right: nothing.

Here’s something I don’t need to write in code: this month’s topic is secret codes. You probably figured that out already. Very smart, you are.

One of the easiest codes to learn is a simple substitution code. To convert your message into a secret code using a substitution code, you simply replace each letter with a letter or number using a consistent pattern. For example, a very simple approach would be to replace each letter with a number corresponding to its place in the alphabet. So ‘A’ would be replaced with ‘1’, ‘B’ with ‘2’ and so on. To say ‘Hello’ in this code, I would write this: 8-5-12-12-15.

That is a simple example. The code can be made much more complicated. There is no need to start numbering at ‘A’, for example. A super smart spy could start with the letter ‘X’ as ‘1’ and continue until the end of the alphabet, wrapping around and continuing at the beginning of the alphabet. An even more super smart spy could number backwards. The smartest of super smart spies might even substitute letters, such as replacing each letter with the one that follows it by 3 letters in the alphabet.

The secret to deciphering all these codes, though, is knowing the key. It does a spy no good to send a coded message if the person on the other end cannot decode it. That is why spies often agree on a secret code and memorize the key in advance.

That way, when one spy sends another spy a message like this:


The other spy knows that it means…. (oh, come on, you can figure that one out, can’t you? Here’s a hint: A=B)

Categories: Secret Codes | Tags: , , , | 1 Comment

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One thought on “Cool Secret Codes For Kids: Substitution Codes

  1. unknown

    this is really cool, HAVE A NICE DAY!

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