The World of Secret Codes
From ancient Roman generals to modern-day cyber warfare, cryptography is the art of keeping secrets in plain sight. Let's start with the big question.
Keeping orders secret from enemies.
Securing your money online.
Watch these two videos on YouTube to understand how encryption changed the world.
Part 1: History of Cryptography
Learn about early encryption and the Enigma machine.
Part 2: How Encryption Works
Understand plaintext, ciphertext, and digital keys.
The Caesar Cipher
Substitution ciphers swap letters for other letters. Julius Caesar used a shift key to keep his battle plans hidden.
A Roman scout sent this message. Shift key: 3.
The first word is HELLO. Find the shift and decode the rest!
The Pigpen Cipher
Substitution doesn't have to be letters-for-letters. Symbols based on a grid position are much harder for a human to read quickly.
Draw the lines surrounding the letter. If there is a dot, add it to your symbol.
Columnar Transposition
Substitution changes letters. Transposition just moves them around! It's like a word scramble, but with a system.
Imagine writing "COMPUTER SCIENCE" into a grid with 3 columns. You write it row by row:
To encrypt it, you read the columns downwards: "CPECN" + "OURIC" + "MTSEE" = CPECNOURICMTSEE.
This message was written into a 3-column grid and then read down the columns. Unscramble it!
Mastering the Terms
Match the correct terms to their definitions. Tap a term, then tap its matching box.
Great Work, Agent! 🎉
You've mastered the basics of cryptography. Now, save your work to submit it for review.
Cryptography & Security
Year 9 Computer Science · Module Complete
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