Computer Science · Encryption Unit · Session 8 of 8

Now do it under the conditions that will actually count.

This session is built directly from the structure NZQA has used across the real 91898 papers: name a real company, choose from a set of mechanism questions, address an opportunity, and explain an impact — then comprehensively tie it together. Treat the assessment section as closed-notes and timed, and don't look past the stop banner until you've finished writing.

Session time: 60 minutes·Homework: 120 minutes, a second full practice write-up

Photo: VD Photography / Unsplash

Executive summary

Goal: produce one full, timed practice answer in the 91898 format, then mark it accurately against a real-style guide.

Time	Segment
0–5 min	Setup: choose your company, re-read the rules
5–45 min	Timed practice assessment (closed notes)
—	Stop. Do not read past the stop banner until you finish.
45–55 min	Self-marking against the guide
55–60 min	Exit question, then Week 2 homework

Before you start

Before you start

This is closed-notes. Before you begin, from memory, list every real company or technology you could write about from this unit (Sessions 1–7, plus your Week 1 homework research). Pick the one you know best — depth beats breadth in every part of this assessment.

About this format

Timed assessment

Rules: closed notes, 40 minutes for the questions below, no internet access. This mirrors NZQA's 91898 "Demonstrate understanding of a computer science concept" achievement standard (3 credits), which is marked on the depth of understanding you show — Achievement, Merit, or Excellence — rather than on ticking off a fixed list of facts. Write in full sentences. Naming a concept is not enough by itself: always explain how and why, and use specifics (a real company, a real mechanism, a real consequence) rather than generic statements.

Question One: your company and its encryption

Choose one real company or organisation from this unit, your Week 1 homework, or another you can confidently explain (for example: Apple, Microsoft, Amazon, Google, Meta/WhatsApp, Tencent/WeChat, ByteDance/TikTok, a bank, or a healthcare provider).

(a) Name your chosen company and briefly explain how it uses encryption. Give two specific examples of what this enables it to do.

Question Two: mechanisms

Choose one of the following:

• Explain how private and public keys work together in public-key encryption, using an example.
• Explain how SHA-256 hashing is used to protect stored passwords, including the role of salting.
• Explain the concerns raised if a website emails a user their original, exact password after they click "forgot password."

(b) Write your answer, explaining the mechanism clearly enough that someone who hasn't taken this course could follow it.

Question Three: opportunity or impact

Choose one of the following:

• Explain one opportunity encryption has provided for your chosen company or for a real technology (for example, in healthcare, banking, or messaging) — a way it has improved functionality, solved a known problem, or made something newly possible.
• Explain one impact of encryption, choosing either a human factor (for example: what should happen to encryption keys and customer data when an organisation closes down) or an ethical issue (for example: the debate over encryption backdoors).

(c) Write your answer, making sure you address the "why it matters" as well as the "what."

Question Four: future-proofing or a major development

Choose one of the following:

• Explain why encryption needs to be future-proofed against quantum computing, and describe the difference in risk between data that is already encrypted and stored versus data that still needs to be encrypted in the future.
• Explain one major real development in computer encryption (for example, the adoption of AES, the rise of HTTPS by default, or the first post-quantum cryptography standards) and why it was important.

(d) Write your answer.

Question Five: comprehensive tie-together

(e) In 3–5 sentences, tie together your answers above: what is the single biggest problem or risk your chosen company's encryption is protecting against, and what would likely happen if that encryption failed or didn't exist?

Stop

Stop here. Finish writing all five answers above before reading any further. The marking guide and model notes below will make it very difficult to judge your own work fairly if you read them first.

Marking guide

Marking guide

91898 is marked holistically across three levels — Achievement (understanding), Merit (in-depth understanding), and Excellence (comprehensive understanding) — not by adding up points per question. Use the descriptions below to judge your own set of answers as a whole, then check each question's specific notes.

• Achievement (understanding): you can correctly describe what encryption does in your chosen example and name the general mechanism involved, even if explanations are a little thin or generic in places.
• Merit (in-depth understanding): your answers explain how and why, not just what — for example, connecting the mechanism to the specific problem it solves, or explaining a consequence with real detail rather than a general statement.
• Excellence (comprehensive understanding): your answers make clear, accurate connections between parts — for example, explicitly linking the mechanism in Question Two to the opportunity or impact in Question Three, or weighing a genuine trade-off (such as both sides of the backdoor debate) rather than presenting only one perspective.

Question One notes

Achievement-level answers correctly name the company and a real use of encryption. Merit-level answers explain specifically what is being protected and from what risk. Excellence-level answers connect the company's use of encryption to a genuine business or user need, not just a generic security statement.

Question Two notes

Watch for the difference between describing a mechanism accurately (Achievement/Merit) and explaining why it's built that way — for example, explaining not just that public and private keys exist, but why the public key can be shared safely and the private key can't (Excellence).

Question Three notes

If you chose the ethical-issue option, an Excellence-level answer should acknowledge there's a genuine argument on both sides (as covered in Session 6), not present the debate as one-sided. If you chose the human-factors option, look for whether you addressed people and process (who is responsible, what should happen to keys) rather than re-explaining the algorithm.

Question Four notes

Look for whether you correctly distinguished data that's already encrypted and stored from data that still needs future encryption (Session 7) — this distinction, drawn directly from real exam papers, is one of the most common places students lose marks by treating "quantum risk" as one single, undifferentiated idea.

Question Five notes

The strongest answers here explicitly reference back to specific mechanisms and impacts named earlier in the same response, rather than introducing a brand new idea — this is what "comprehensive" understanding looks like in practice.

Exit question

Looking at your own marked answers: which question would you improve first if you sat this again next week, and specifically what would you add?

Key terms

• Achievement
• Merit
• Excellence
• 91898
• comprehensive understanding

Week 2 homework

Homework

Time budget: roughly two hours, self-paced.

The task: a second full practice write-up

Repeat the full Question One–Five format above, under the same closed-notes, 40-minute time limit, but choose a different real company or technology than the one you used in class (for example, if you wrote about a messaging app in class, choose a bank, a healthcare provider, or a different named company this time).

1. Complete all five questions in the same format, allowing yourself 40 minutes.
2. Mark your own answers against the guide above, being as honest as you would want a teacher to be.
3. Write two sentences: one on what you did better this time than in class, and one on what still needs work.
4. Bring your marked answers to your teacher or supervisor to check your self-assessment against theirs.

1. 1
2. 2
3. 3
4. 4
5. 5
6. 6
7. 7
8. 8

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