Ethereum Flashcards

What is the role of the 'receipts trie' in an Ethereum block?

Answer: It stores the outcome of each transaction including logs and gas used, enabling light client verification

The receipts trie root is committed in the block header, letting clients verify transaction outcomes without replaying them.

Which Solidity visibility modifier makes a function only callable from within the contract or derived contracts?

Answer: internal

The 'internal' modifier restricts access to the contract itself and any contract that inherits from it.

What attack vector does the 'checks-effects-interactions' pattern in Solidity primarily defend against?

Answer: Reentrancy attacks

By updating state before making external calls, the pattern prevents a malicious contract from re-entering a function in an inconsistent state.

In Ethereum's EIP-4844 (Proto-Danksharding), what new transaction type was introduced?

Answer: Blob-carrying transactions

EIP-4844 introduced type-3 blob-carrying transactions that attach temporary data blobs to reduce L2 data availability costs.

What is 'gas stipend' in the context of Ethereum's transfer() and send() functions?

Answer: A fixed 2300 gas forwarded to the recipient to prevent reentrancy while allowing basic logging

transfer() and send() forward exactly 2300 gas, enough for a log event but insufficient to execute complex code or re-enter.

What does EIP-2930 (Optional Access Lists) accomplish?

Answer: Allows transactions to pre-declare storage keys and addresses they will access, reducing gas costs for those slots

EIP-2930 lets transactions specify an access list upfront, charging lower warm-access gas for those slots during execution.

In Ethereum's beacon chain, what is an 'attestation'?

Answer: A validator's signed vote confirming a specific block as the head of the chain and a checkpoint as finalized

Attestations are validators' LMD-GHOST and Casper FFG votes aggregated per slot to determine the canonical chain.