# Quiz: Ethereum Interactive Lecture (Post-Quiz) ## BSc Blockchain, Crypto Economy & NFTs **Lecture Covered**: Ethereum Interactive Lecture (90-minute interactive session, lecture-first 60/30, Google-Doc analogy, HelloWorld deploy on Remix VM) **Duration**: 5 minutes **Total Points**: 70 points **Question Types**: 7 multiple choice (10 pts each) **Concept-based**: All questions test understanding, NOT possession of a deployed contract address. A student who never opened Remix can score 100%. Reference: ../../prd.json story D5 Security brief: ../instructor_kit/security_brief.md --- ## Multiple Choice Questions (70 points total) ### Question 1 (10 points) **Topic**: The Google-Doc analogy Throughout the lecture we treated Ethereum as "a shared, append-only Google Doc where every edit must be signed and pays a small fee". Which property of an actual Google Doc does this analogy DELIBERATELY break? A) Identity (Google identity vs an Ethereum account) B) Editability (Google Docs allow editing existing cells; Ethereum is append-only) C) Sharing (both are accessible from many places) D) Storage (both persist across sessions) **Correct Answer**: B **Explanation**: A live Google Doc lets you edit any cell at any time. Ethereum is append-only: once a transaction is mined, you cannot edit it. New transactions create new state, but they never overwrite the historical record. This is the limit of the analogy and it is the slide titled "Where the Google-Doc analogy breaks". See ../instructor_kit/security_brief.md and the slides. --- ### Question 2 (10 points) **Topic**: Private vs shared chain You deployed `HelloWorld` on Remix VM in the workshop. Your friend on a different laptop also deployed `HelloWorld` on Remix VM in the workshop. Can your friend see your contract? A) Yes, both contracts are on the same chain B) Yes, but only if your friend has your contract address C) No, Remix VM is a chain that runs entirely inside YOUR browser tab; your friend's tab has its own separate chain D) No, but they could see your contract if you both connected to the same RPC endpoint **Correct Answer**: C **Explanation**: The Remix VM in-browser chain runs in JavaScript inside the loaded Remix tab. It is a private chain visible only to that tab. Closing the tab erases the chain. The instructor anchor demo (D11, minutes 35 to 38 of the lecture) demonstrated the contrast: Sepolia is shared globally, Remix VM is private to your tab. See ../lab_guide.md "Why your chain is private". --- ### Question 3 (10 points) **Topic**: Gas In the lecture we framed gas as "the per-character fee" in the Google-Doc analogy. What is the operational role of gas on a real Ethereum chain? A) It encrypts transaction data B) It measures and limits computational work, prevents infinite loops and spam, and compensates validators C) It only determines transaction priority D) It converts ETH into fiat currency **Correct Answer**: B **Explanation**: Gas serves multiple purposes simultaneously. It measures the computational complexity of operations, prevents denial-of-service via infinite loops by capping execution, compensates validators for the work they perform, and creates a fee market for limited block space. --- ### Question 4 (10 points) **Topic**: Test wallet hygiene Suppose you installed MetaMask in class as part of the optional Sepolia level-up. You generated a 12-word seed phrase. After class, you remembered that you have been meaning to set up a wallet for real ETH purchases. May you import that same seed phrase into a hardware wallet for real-money use? A) Yes, the seed phrase is just for cryptographic key generation; it does not matter where it was generated B) Yes, as long as you change the password C) No. The seed was generated on classroom infrastructure that may be compromised. Real money requires a fresh seed generated on a clean machine. D) No, but only if you used the wallet for any Sepolia transactions **Correct Answer**: C **Explanation**: Per the security brief (../instructor_kit/security_brief.md): TEST WALLET ONLY, NEVER REUSE THIS SEED. A seed phrase is the master key. One leak compromises every chain that derives addresses from it. A workshop wallet is single-use and must never be reused for real funds. Generate a fresh seed on a clean machine for any real-money wallet. --- ### Question 5 (10 points) **Topic**: First principles vs tooling Which of the following statements correctly identifies a FIRST-PRINCIPLES property of Ethereum (true regardless of tooling), as opposed to a tool-specific detail? A) The Remix IDE is at remix.ethereum.org B) MetaMask uses a 12-word seed phrase C) Every state-changing operation on Ethereum requires a signed transaction from an account that pays gas D) Etherscan is the standard block explorer **Correct Answer**: C **Explanation**: The signed-transaction-plus-gas requirement is built into the Ethereum protocol. It is true on every Ethereum-compatible chain regardless of which IDE, wallet, or block explorer you use. The other three options are choices of specific tools that could be replaced with alternatives without changing the underlying protocol. --- ### Question 6 (10 points) **Topic**: EVM determinism In the lecture we said the Ethereum Virtual Machine is "deterministic and replicated". What is the consequence of breaking determinism (e.g. allowing a contract to read the wall-clock time of the validator that runs it first)? A) Contracts would be slower B) Different validators would compute different results, so they could not agree on the new world state, breaking consensus C) Gas costs would be lower D) Solidity would not compile **Correct Answer**: B **Explanation**: Determinism is what allows thousands of validators to run the same transaction independently and arrive at the same answer. If a contract could read the wall-clock or do file I/O, each validator would see a different value, the post-transaction state would diverge, and the network would split. This is why Solidity has no `time.now()` (only block timestamps from the proposer), no random number generator, and no network or filesystem primitives. --- ### Question 7 (10 points) **Topic**: Phishing and Chrome extensions Two days after class, you see an email titled "MetaMask: Action Required". The email links to `metamask-security.xyz` and asks you to verify your seed phrase to "secure your wallet". What is the safe action? A) Click the link, since the email looks official B) Type the seed phrase into the linked page, but only your test wallet seed C) Delete the email. Real wallets never ask for the seed phrase via email or web form. The legitimate domain is `metamask.io` (anything else is phishing). D) Forward the email to MetaMask support so they can investigate **Correct Answer**: C **Explanation**: Wallet vendors NEVER ask for your seed phrase via email, chat, or web form. Any prompt to "verify" or "restore" a seed outside the wallet's own native restore flow is a phishing attack. The look-alike domain (`metamask-security.xyz` vs the legitimate `metamask.io`) is the classic tell. See `../instructor_kit/security_brief.md` for the full phishing playbook. --- ## Answer Key Summary | Q | Answer | Topic | |---|--------|-------| | 1 | B | Google-Doc analogy limit (append-only) | | 2 | C | Private vs shared chain | | 3 | B | Gas | | 4 | C | Test wallet hygiene | | 5 | C | First principles vs tooling | | 6 | B | EVM determinism | | 7 | C | Phishing and Chrome extensions | ## Scoring - 7 of 7 correct: 70 points (100%) - Excellent - 6 of 7 correct: 60 points (86%) - Strong - 5 of 7 correct: 50 points (71%) - Adequate (above the 70% bar in the PRD) - 4 of 7 correct: 40 points (57%) - Revisit the slides - Below 4: revisit slides 1 to 5 (Google-Doc analogy), slides 14 to 17 (private vs shared chain), and slide 9 (TEST WALLET ONLY) ## Note for Non-Deployers If you did not complete a Remix VM deploy in class (you arrived late, your laptop blocked Remix, the room had connectivity problems), this quiz is still scorable. None of the questions require possession of a contract address. The lecture's pedagogical claims survive without the artifact, by design. See ../instructor_kit/security_brief.md for the duty-of-care framing and ../instructor_kit/fallback_plan.md for the fallback procedures used during the class.