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What is Encryption?
What is Encryption?
Every time you browse the internet, use an app, send a message, or make a payment online, your device is sending and receiving information. This data travels through networks that connect millions of computers around the world. But not all networks are secure. Hackers and cybercriminals can intercept data, especially on public Wi-Fi or poorly protected systems. That’s where encryption comes in. Encryption is one of the most important tools used in cybersecurity—it helps keep your personal information safe by scrambling it into a code that only the right person can read. This lesson explores what encryption is, why it’s used, how it has evolved from ancient times to the modern internet, and how it protects us in everyday digital life.
Encryption turns plaintext into ciphertext.
It keeps your data private when it travels across the internet.
A key is needed to decode the encrypted message.
🎯 Learning Objectives
🎯 Learning Objectives
By the end of this lesson, you will be able to:
Define encryption and explain its purpose in digital communication.
Describe how plaintext becomes ciphertext using a key.
Understand the risks of sending unencrypted data over a network.
Explain how the Caesar cipher works as a basic encryption method.
Compare classical and modern encryption methods.
Identify the difference between symmetric and asymmetric encryption.
Describe how encryption can be attacked using brute-force or cryptanalysis.
Recognise how encryption is used in real life through tools like HTTPS and end-to-end encryption.
Key Terms
Key Terms
Encryption: The process of turning readable data (plaintext) into secret code (ciphertext) to keep it private.
Plaintext: The original, readable message before it is encrypted.
Ciphertext: The scrambled, unreadable version of a message after encryption.
Key: A piece of information used to encrypt or decrypt data; without it, the message stays unreadable.
Caesar Cipher: A basic encryption method that shifts letters in the alphabet to hide a message.
Symmetric Encryption: A type of encryption that uses the same key to lock and unlock the message.
Asymmetric Encryption: A type of encryption that uses two different keys—one to lock (public key) and one to unlock (private key).
Brute-force Attack: A way to break encryption by trying every possible key until the correct one is found.
Cryptanalysis: The method of studying encrypted messages to find patterns or weaknesses.
HTTPS: A secure version of the HTTP protocol that encrypts data between your browser and a website.
End-to-End Encryption: A type of encryption where only the sender and the receiver can read the message—even the service provider cannot see it.
Reflection:
Why is it important to protect personal data like messages or passwords when using the internet?
🛡️ Why Do We Need Encryption?
🛡️ Why Do We Need Encryption?
The internet is like a huge, shared highway—and your data is like a car driving on it. If that data isn't locked (encrypted), anyone can look inside. This is especially risky when using public Wi-Fi in cafés, airports, or schools. Hackers can intercept unprotected data and steal sensitive details. Encryption acts like a shield—keeping your emails, passwords, and payment information safe even if someone tries to grab it on the way.
Key Points:
Key Points:
Without encryption, intercepted data is readable.
Encryption protects sensitive information like passwords and credit card numbers.
It’s especially important on public or shared networks.
Reflection:
Where do you think your data is most at risk: at home, at school, or in a public place? Why?
Classical Encryption: Caesar Cipher
Classical Encryption: Caesar Cipher
Before modern computers, people still needed ways to send secret messages. One of the oldest examples is the Caesar Cipher, used by Julius Caesar.
It works by shifting each letter forward in the alphabet by a set number. Although this method is simple and easy to understand, it’s also easy to crack—especially if someone knows you’re using a cipher.
Key Points:
Key Points:
The Caesar Cipher shifts letters in the alphabet to encode a message.
It’s an example of a substitution cipher.
It helps us understand the basic concept of changing readable text into unreadable form.
Reflection:
If someone intercepted a Caesar Cipher message, how could they figure it out?
Modern Encryption
Modern Encryption
Modern encryption is much more complex than ancient ciphers. It uses long encryption keys—often 128 bits or more—and powerful mathematical algorithms to make data secure. Even a small change in the message or the key can produce completely different ciphertext. Two main types are used today:
Symmetric encryption: The same key is used to lock and unlock the data.
Asymmetric encryption: One key locks the data (public key), and a different key unlocks it (private key).
Key Points:
Key Points:
Modern encryption uses complex algorithms and long keys.
It is designed to resist brute-force attacks and pattern detection.
Symmetric and asymmetric encryption are both used in different situations.
Reflection:
Why do you think asymmetric encryption is useful for websites and online shopping?
How Can Encryption Be Broken?
How Can Encryption Be Broken?
Even though encryption is powerful, people still try to break it. There are two main ways:
Brute-force attacks try every possible key until one works. This is slow and often impossible with strong encryption.
Cryptanalysis looks for patterns or flaws in the encryption. Strong encryption avoids patterns to stop this.
Breaking modern encryption takes so much time and power that it's not realistic without very weak keys or serious mistakes.
Key Points:
Key Points:
Brute-force means attempting to guess every possible key.
Cryptanalysis means looking for patterns or weaknesses.
Strong encryption makes both of these methods nearly useless.
Reflection:
What do you think makes an encryption method strong or weak?
Encryption in Everyday Life
Encryption in Everyday Life
Even if you don’t realise it, encryption is protecting you all the time. Websites that use HTTPS encrypt all data sent between your device and the server. Messaging apps like WhatsApp and Signal use end-to-end encryption, meaning only the sender and receiver can read the messages. Online banks and shops also use encryption to keep your data safe.
Key Points:
Key Points:
A padlock icon in your browser means the site uses HTTPS (encrypted).
Messaging apps often use end-to-end encryption.
Encryption helps protect privacy and prevent identity theft.
Reflection:
Identify a website or app you use that uses encryption.
Revision Section
Revision Section
What is Encryption?
Encryption protects data by turning it into unreadable code using a secret key.
Without encryption, sensitive information like passwords or credit cards can be stolen.
Simple ciphers can be cracked easily; modern encryption uses maths and long keys.
HTTPS and secure messaging apps use encryption to keep data safe.
Why Do We Need It?
Protects private data from hackers or snoopers, especially on public networks.
Classical Ciphers
Example: Caesar Cipher shifts letters in the alphabet.
Easy to crack but shows the basic idea of encryption.
Modern Encryption
Uses long keys and complex maths.
Two types: symmetric and asymmetric.
How Is Encryption Broken?
Brute-force attacks = try all keys.
Cryptanalysis = find patterns.
Strong encryption avoids both.
Real-World Uses
HTTPS websites
Messaging apps (e.g., WhatsApp)
Online shopping and banking
Comprehension Questions
Comprehension Questions
Copy the questions into your WBK. Answer them in complete sentences. Do not copy-paste your answers and do not use AI.
What is encryption and why is it used?
What is the difference between plaintext and ciphertext?
What is the role of a key in encryption?
Why is encryption especially important on public networks like café Wi-Fi?
How does encryption protect your data during transmission?
How does the Caesar cipher work, and why is it not secure today?
What are the main differences between classical and modern encryption?
What is symmetric encryption, and how does it work?
What is asymmetric encryption, and how is it different from symmetric encryption?
Why do modern encryption systems use very long keys?
What is a brute-force attack, and why is it unlikely to succeed against modern encryption?
What is cryptanalysis, and how does it try to break encryption?
What does the padlock icon in your web browser tell you?
What is end-to-end encryption, and what does it protect?
Name one real-world app or website that uses encryption and explain how it keeps your data safe.
Individual
Individual
Try a Caesar Cipher
Search: “online Caesar cipher tool”
✍ In your WBK:
Write your message (e.g. “Hello class”)
Show the encrypted version (use shift 3)
Explain how this cipher works
Add 1 image of a padlock or HTTPS browser symbol
Title the page: Lesson 5 Summary: Encryption and Security
Pair
Pair
Secure or Not?
Search: 3 websites you use (e.g. YouTube, Gmail, school site)
✍ In your WBK:
Write if each site uses HTTPS (check for padlock)
Explain why this matters for safety and privacy
Group
Group
Create a Password Guide
Search: “tips for strong passwords”
✍ In your WBK:
Make a list of 5 rules for strong passwords
Add 2 real consequences of weak passwords (e.g. account hack)
Include a small drawing or image
Exam-style Questions
Exam-style Questions
(2 marks) State one reason why encryption is important when using online banking.
(3 marks) Describe how the Caesar cipher works and explain why it is easy to break.
(3 marks) Explain how HTTPS protects users when they enter data into a website.
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