Cryptography for Kids | Activities & Worksheets

How to explain encryption to a child?

Cryptography is a serious science for technologists but can become a brain-teasing fun activity for kids. Parents and teachers try to introduce cryptography to kids not just to teach them cryptography but because cryptography is a great brain development tool too. It improves the reasoning and logical ability of a child.

Let’s explore everything about cryptography with fun cryptography activities and worksheets.

Note: The language of this post talks directly with the kids. Parents and teachers can use & execute this content the way they feel better.

Fun cryptography activity 1

I have a question: Can you read? Do you know reading? Haaa… silly question that is. You are already reading this post and I am asking if you can read it.

Ok, so I believe you can read, so please read the following.

You will be able to download this in worksheet format at the bottom of this post.

Na na… Don’t pronounce the alphabet. Read the words. Can you? Ah! So I won. Just a while back you said you can read. But you could not read the above text.

Ok Ok… I agree you can read, but then why can’t you read the above text?

Because this text is “Encrypted”, or in simple words, it’s morphed to make it secure.

This entire science of securing communication, so that only the sender and the intended receiver know the right message, is called “Cryptography”.

Cryptography or cryptology is a mix of Maths, Computer science, communication technology, electrical and electronics.

Fun cryptography activity 2: Securing a message

Do you know “Do Jasoos”? Jasoos Chinki and Jasoos Chintu.(Jasoos = spy). The two super spies. Both spies have a very challenging and important task with them.

Jasoos Chinki has got a box of Kaju Katli(yes, a box full of sweets) and she had to keep it safe from others. But she wanted to inform he whereabouts of the box to Jasoos Chintu.

Jasoos Chinki has prepared a message

“In The Top Drawer”

But how would they communicate this? Telling directly, or sending a chit are not safe options.

So Jasoos Chinki has used a trick. She shifted all the characters of her message by 1.

What comes after I? That’s J. And after N? Correct, O. That way she shifted all the characters by one.

So the message became

“Jo Uif Upq Esbxfs”

So funny, no?

Here the original message is called “Plain Text”.

And the message that you generate after securing it is called “Cipher Text”.

This process of converting plain text to cipher text is called “Encryption”.

Now Jasoos Chintu does the exact reverse to what Jasoos Chinki has done.

He will go one step back and put the previous characters of each of the characters of the cipher text.

So he gets to know that Kaju Katli is in the top drawer and he is ready to eat!

So what Jasoos Chintu has done here? He has converted Cipher text to Plain text again.

And this process of converting a cipher text to plain text is called “Decryption”.

You will get many fun exercises to convert plain text to cipher text and cipher text to plain text or say Encryption and decryption in the cryptography worksheet at the bottom.

Fun cryptography activity 3: The concept of Key

This secure communication went well and both the jasoos were enjoying the Kaju Katli until one day when Hacku Hana “Interrupted” and “Cracked” their encryption.

Hacku Hana now knows where both the jasoos are keeping their Kaju Katli.

As Jasoos Chintu sensed this “Cracking”, they started changing the location of the box every time after use.

The study of cipher text to get the original message without knowing the key is called cryptanalysis or cracking or code breaking.

Jasoos Chinki will change the location and will send the location info in “Encrypted form” using cryptography.

But Hacku Hana has learned that they are increasing the character value by one every time to encrypt the message. So it was easy to know the location every time. In other words Hacku Hana now knows the “Key” to encrypt and decrypt the message.

Both the Jasoos were worried, but soon they found a better way to secure their message. They agreed to change the number of increments.

Someday they will increase the character by 4. The key will be 4. The message will be as below:

So B will become F.
B to F
J to N
P to T
And so on.

That number is called the “Key”. Sometimes they will keep the key 2 the other day it would be 7.

This method of cryptography where we shift the alphabet by a key is known as Caesar Cipher. That’s one kind of cryptography algorithm along with many others.

So Jasoos Chinki, Jasoos Chintu, and their box of Kaju Katli are safe, till Hacku Hana understands this new “pattern” of cryptography used by them.

Let’s wait to know what happens with them. Till then you can try our cryptography worksheet.

BTW let me tell you one last thing. Not just jasoos Chinki and Chintu, cryptography is very useful in keeping us secure in banks, emails, passwords, online shopping, messaging etc. The algorithms would be very very complex though. Cryptography works mostly behind the scenes, so we don’t know much about its existence.