Smart Contracts & Decentralized Applications Flashcards

Which Solidity visibility modifier makes a function callable only from within the contract itself and not from derived contracts?

Answer: private

The `private` modifier restricts function access to the defining contract only, excluding derived contracts.

In Ethereum smart contracts, what is a 'reentrancy attack'?

Answer: An external contract recursively calling back into the victim contract before state updates complete

Reentrancy attacks occur when a malicious contract calls back into the victim before its state (like balance) is updated, draining funds.

What does the ERC-721 standard define?

Answer: A standard for non-fungible tokens (NFTs) on Ethereum

ERC-721 defines the standard interface for non-fungible tokens, where each token has a unique identifier.

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

Answer: Proxy pattern

The proxy pattern delegates calls to a logic contract while keeping state in the proxy, allowing the logic to be replaced without changing the storage address.

What is the purpose of the `require` statement in a Solidity smart contract?

Answer: To validate conditions and revert the transaction if the condition is false

`require` validates inputs or conditions and reverts the transaction with an optional error message if the condition fails.

In the context of dApps, what role does IPFS primarily serve?

Answer: Providing decentralized storage for large files and front-end assets

IPFS (InterPlanetary File System) provides content-addressed, decentralized storage commonly used for dApp front-ends and NFT metadata.

What is 'gas stipend' in the context of Ethereum smart contract calls?

Answer: The fixed amount of gas forwarded when a contract sends Ether using `transfer` or `send`

Solidity's `transfer` and `send` forward only 2,300 gas, preventing reentrancy but limiting what the recipient contract can do.