# Chapter 1: Introduction to Cryptography#

Imagine you’re passing secret notes in class. That’s cryptography in a nutshell - keeping secrets secret. But instead of folding paper into fancy shapes, we use math to scramble our messages.

## What is Cryptography?#

Cryptography is like a secret language for your digital life. It’s the art of writing or solving codes to protect information. Think of it as a magical lock for your data.

## A Brief History#

Ancient Egyptians used picture symbols to hide messages.

Julius Caesar shifted letters to confuse enemies.

World War II saw the rise of machine-based encryption like the Enigma.

Today, cryptography protects everything from your texts to your online shopping.

## Why It Matters#

In our digital world, cryptography is everywhere:

It keeps your WhatsApp messages private.

It secures your online banking.

It protects your passwords when you log into websites.

It even makes cryptocurrencies like Bitcoin possible.

## The Building Blocks#

Cryptography has three main tools in its toolbox:

**Symmetric-key cryptography**: Like a secret handshake between friends.**Public-key cryptography**: Think of a magical mailbox anyone can put letters in, but only you can open.**Hash functions**: Imagine a paper shredder that always makes the same confetti pattern for the same document.

## What We Learned#

Cryptography is about keeping information secret and secure.

It has a long history, from ancient civilizations to modern digital systems.

Cryptography is crucial in our daily digital interactions.

There are three main types of cryptographic tools: symmetric-key, public-key, and hash functions.

## Quick Check: Did You Get It?#

Let’s see if you caught the main ideas:

What’s the secret language of computers called? (Hint: It starts with ‘C’)

What do we call the key that both sender and receiver share? (Hint: It sounds like ‘symmetric’)

What’s the digital equivalent of a fingerprint? (Hint: It starts with ‘H’)

Think about your answers, then check below!

## Click to see the answers

Cryptography

Symmetric key

Hash function

Great job if you got them all!