What Exactly Encription is?

When you open messaging apps like WhatsApp, you probably see alerts like:

Your messages are end-to-end encrypted.

But what does encryption actually mean?

What really happens technically when you send a message?

Imagine This Scenario

Suppose I want to send a secret message to my friend.

Before sending anything, I secretly tell my friend:

To understand my messages, move every letter one step backward in the alphabet.

So if my friend sees:

B

They know it actually means:

A

Because:

A → B
B → C
C → D

Every letter is shifted by one.

Now suppose my real message is:

HELLO

Before sending it, I transform every letter using the same rule:

H → I
E → F
L → M
L → M
O → P

So the encrypted message becomes:

IFMMP

Now I give YOU the paper containing:

IFMMP

and ask you:

Take this to my friend.

If someone steals the paper while you are carrying it, they will only see:

IFMMP

which looks meaningless unless they know the secret rule.

My friend, however, already knows the rule:

Move every letter one step backward.

So they can decode the message:

I → H
F → E
M → L
M → L
P → O

and recover:

HELLO

That secret rule is basically the key.

This Is Basically Encryption

Encryption means:

Transforming readable information into another form using a secret rule or key.

The original readable message is called:

Plain Text
And the transformed unreadable version is called:

Cipher Text
So in our example:

HELLO  → Plain Text
IFMMP  → Cipher Text
But Computers Do Not Understand Letters

Computers do not actually understand:

H
E
L
O

Computers only understand:

bits
0s
1s

As we explained in the previous article, every character inside a computer becomes a number.

For example:

H = 72
E = 69
L = 76
O = 79

And those numbers themselves become binary:

72 = 01001000
69 = 01000101

So inside a computer, your messages are really just numbers and bits.

Encryption Inside Computers

So inside a computer, your messages are really just numbers and bits.

Encryption at the computer level is basically taking those numbers and transforming them into other numbers using a reversible mathematical rule.

In simple words:

The computer changes the original numbers into different numbers in a way that can later be reversed using the correct key or formula.

For example, imagine we have a number like:

1

In binary, that becomes:

00000001

Now, suppose the computer applies a secret rule like:

add 5

So:

1 + 5 = 6

And now the stored value becomes:

00000110

Someone looking at the encrypted value only sees:

6

not the original:

1

To recover the original value, the receiver uses the reverse operation:

6 - 5 = 1

and the original data comes back again.

Modern encryption systems are much more advanced than simple addition and subtraction, but the core idea is still similar:

1. – take original data
2. – transform it using mathematics
3. – Use a secret key
4. – and make it unreadable without the correct way to reverse it

That transformed unreadable data is what we call:
Encrypted Data