CBSA Smart Contract Design 2

Question 1

Which design pattern separates a smart contract's logic from its data storage to enable upgradability?

Accepted Answer

Proxy pattern

Answer

The proxy pattern delegates calls to a logic contract while keeping state in a separate storage contract, allowing logic upgrades without migrating data.

Question 2

What is a primary security risk of using 'tx.origin' for authorization in a Solidity smart contract?

Accepted Answer

It exposes the contract to phishing attacks via malicious intermediary contracts

Answer

A malicious contract can trick the original sender into calling it, and tx.origin still returns that user's address, bypassing intended authorization checks.

Question 3

In smart contract design, what does the 'check-effects-interactions' pattern primarily prevent?

Accepted Answer

Reentrancy attacks

Answer

By updating internal state (effects) before calling external contracts (interactions), the pattern prevents reentrant calls from exploiting stale state.

Question 4

Which Ethereum opcode is used internally when a contract sends Ether using the 'transfer' function, and what is its gas stipend?

Accepted Answer

CALL with 2300 gas

Answer

The 'transfer' function uses the CALL opcode but forwards only 2300 gas, which is enough for a log event but prevents most reentrancy.

Question 5

What is the purpose of the 'circuit breaker' (emergency stop) pattern in smart contract design?

Accepted Answer

To pause contract functionality when a vulnerability is detected

Answer

A circuit breaker allows an authorized admin to halt critical functions so funds can be protected while a vulnerability is investigated and fixed.

(CBSA) Certified Blockchain Solution Architect Practice Test

(CBSA) Certified Blockchain Solution Architect Practice Test

CBSA Smart Contract Design 2