CBCP Smart Contracts and dApps 2

Question 1

Which vulnerability allows an attacker to repeatedly call a function before the first execution finishes, draining a contract's funds?

Accepted Answer

Reentrancy attack

Answer

Reentrancy attacks exploit the ability to re-enter a function before its state is updated, as famously demonstrated by The DAO hack in 2016.

Question 2

What Solidity design pattern places the 'check-effects-interactions' principle to prevent reentrancy?

Accepted Answer

Update state variables before external calls

Answer

The checks-effects-interactions pattern requires updating contract state before making any external calls to prevent reentrancy.

Question 3

In Ethereum, what does the 'fallback' function do when a contract receives Ether with no matching function signature?

Accepted Answer

It executes as the default handler for unmatched calls or plain Ether transfers

Answer

The fallback function is invoked when no other function matches the call data, or when Ether is sent without any call data.

Question 4

Which ERC standard is commonly used for non-fungible tokens (NFTs) on Ethereum?

Accepted Answer

ERC-721

Answer

ERC-721 defines the standard interface for non-fungible tokens, where each token has a unique identifier and cannot be exchanged 1:1 with another.

Question 5

What is the primary role of an oracle in a smart contract ecosystem?

Accepted Answer

To provide off-chain real-world data to on-chain smart contracts

Answer

Oracles act as bridges that fetch and verify external data (prices, weather, sports scores) and deliver it to smart contracts that cannot access the internet directly.

CBCP - Certified Blockchain Professional Practice Test

CBCP - Certified Blockchain Professional Practice Test

CBCP Smart Contracts and dApps 2