Yr5 Term 1.1.5 Codebreaker – Dyson-Mills Computer Science

Welcome to Year 5 Computing — Lesson 5! 🔐

Today we are becoming codebreakers! We will learn how secret messages are sent across the internet using Encryption, and we will try to crack the classic Caesar Cipher and Random Substitution Ciphers!

Step 1: Keyboard Warm-up ⌨️ (10 Mins)

Click here to warm up your fingers on our typing studio: Start Typing Practice on Ndovu.
Focus on correct finger placement and accuracy. Keep practicing until your teacher brings the class together!

Step 2: Interactive Caesar Cipher Simulator 🕵️‍♂️ (15 Mins)

A Caesar Cipher is one of the oldest encryption methods. It works by “shifting” the alphabet by a certain number. Test it out below by typing a secret message and dragging the shift slider!

Caesar Cipher Encryptor

Your Secret Message:

Shift Value: 3

Encrypted Output (Cyphertext):

1. How does a Caesar cipher work, and how do you use a “shift value” to encrypt a message?

2. How can “frequency analysis” (looking at the most common letters in a language, like ‘E’) help you crack a random substitution cipher?

3. Why is strong encryption essential for daily life on the internet (like online banking or secure messaging)?

Step 3: Cracking Codes on Code.org 🚀 (20 Mins)

Now that you understand how a shift cipher works, it is time to try breaking a Random Substitution Cipher! You will need to use your detective skills and frequency analysis to figure out which random letters match up with the real alphabet.

Mission: Launch Code.org Encryption Unit

Click the button below to sign in. Once signed in, navigate to your assigned Encryption section!

Launch Code.org Sign In ➔

Step 4: Log Off and Reflect 👋 (5 Mins)

Exit Ticket: Why are simple substitution ciphers considered weak, and why do we need much stronger encryption today?
Log out securely and tidy your desk space!