CCE Smart Contracts and Ethereum 2

Question 1

What does the ERC-20 token standard define?

Accepted Answer

A common set of rules for creating interchangeable (fungible) tokens on Ethereum

Answer

ERC-20 is a technical standard that defines a common interface for fungible tokens on Ethereum, enabling any compliant token to be used interchangeably across wallets and exchanges.

Question 2

What is the key difference between an Externally Owned Account (EOA) and a contract account in Ethereum?

Accepted Answer

EOAs are controlled by a private key; contract accounts are controlled by smart contract code

Answer

EOAs are controlled by private keys held by users and can initiate transactions, while contract accounts are controlled by their deployed smart contract code and can only respond to incoming transactions.

Question 3

What is a 'reentrancy attack' in the context of smart contracts?

Accepted Answer

An attack where a malicious contract calls back into the victim contract before the first execution completes

Answer

A reentrancy attack occurs when a malicious contract recursively calls back into the vulnerable contract before the first call's state updates are finalized, allowing funds to be withdrawn multiple times.

Question 4

What does the 'payable' keyword do in a Solidity smart contract?

Accepted Answer

It allows a function or address to receive Ether as part of a transaction

Answer

The 'payable' modifier in Solidity allows a function or address to receive Ether; any Ether sent to a non-payable function will cause the transaction to revert.

Question 5

What is the primary purpose of events in Ethereum smart contracts?

Accepted Answer

To log information to the blockchain that off-chain applications can listen to and act upon

Answer

Events emit logs stored on the blockchain that are not accessible by other contracts but can be efficiently monitored by off-chain applications such as DApp frontends or indexing services.

(CCE) Certified Cryptocurrency Expert Practice Test

(CCE) Certified Cryptocurrency Expert Practice Test

CCE Smart Contracts and Ethereum 2