Computer Science · Encryption Unit

Encryption, taught through the companies and devices that actually run on it.

A garage door remote, a tap-and-go card reader, a "forgot password" email, a phone that a government wanted unlocked. Over four sessions and a homework week, then four more, you'll learn what these have in common — and pick up plaintext and ciphertext, symmetric and public-key encryption, HTTPS, hashing, human factors, and future-proofing against quantum computers along the way.

Format: 4 sessions + homework, twice·Total: 8 hours class, 4 hours homework·No programming experience required

Executive summary

Start here. Read the sessions in order. Keep a separate answer document, attempt each activity before checking the answers, and correct mistakes in a different colour. Every session includes explanations, a diagram, a worked example, practice and feedback.

Week	Student notes	Class time	Homework
1	1. What encryption protects	60 min	—
1	2. Symmetric encryption	60 min	—
1	3. Public-key encryption and HTTPS	60 min	—
1	4. Hashing and passwords	60 min	120 min
2	5. Encryption in everyday tech	60 min	—
2	6. The human side of encryption	60 min	—
2	7. Future-proofing encryption	60 min	—
2	8. Practice assessment	60 min	120 min
	Total	8 hours	4 hours

Why real companies, not a case study

Note

This unit is deliberately built around named, real companies and technologies — Apple, Google, Meta/WhatsApp, banks and card networks, garage door manufacturers, hospitals — rather than one running fictional case study. That's not just variety: it's exam technique. This course exists to prepare you for NZQA's Level 2 Digital Technologies achievement standard 91898, and every past paper for the encryption topic asks you to name a real company or technology and describe specifically how it uses encryption. Practising with real examples throughout the unit means you'll already have several ready to write about on the day, instead of trying to invent one under time pressure.

This unit deliberately does not link external videos the way the Computer Security unit does — instead of curating a list that can't be re-checked every year, each session carries its own diagrams and worked examples, so the notes stand on their own. If you'd like to add trusted video links locally, they can be inserted under each session's diagram.

Assessment status

Timed assessment

Session 8 is built directly from the structure of NZQA's real 91898 exam papers (2019, 2020, 2021, 2023 and 2025), so its format and question style should closely match what you'll see in the actual assessment. It is still practice, not the real thing — your teacher's marking guide and the current year's assessment specification always take precedence over anything here.

What to submit to yourself

• Completed activities and a glossary of key terms.
• Week 1 homework: a short piece of research on one real company's use of encryption.
• Week 2 homework: a full practice write-up in the 91898 answer format, self-marked against the guide.
• The marked practice assessment from Session 8, with corrections.

Move on when you can explain each session's exit question without copying. If you can't, revisit the worked example and rewrite your explanation.

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Start · Session 1: What encryption protects →