NFT Allowlist and Presale Mechanics 2

Question 1

What is the key architectural difference between signature-based allowlisting and Merkle tree allowlisting?

Accepted Answer

Signature-based requires a trusted backend signer to issue per-user signatures; Merkle-based uses a precomputed tree with a single on-chain root

Answer

In signature-based allowlisting a trusted signer generates individual ECDSA signatures for each user, while Merkle trees precompute the full tree off-chain and store only the root, requiring no active signer at mint time.

Question 2

In an ECDSA signature-based allowlist, what does the NFT smart contract verify during a mint call?

Accepted Answer

That the address recovered from the signature using ecrecover() matches the stored trusted signer address

Answer

The contract hashes the message, calls ecrecover() with the signature, and checks that the recovered address equals the stored trustedSigner variable, confirming the signature was created by an authorized party.

Question 3

What is a signature replay attack in the context of NFT allowlists, and how is it prevented?

Accepted Answer

Submitting a valid signature multiple times to mint more NFTs than intended; prevented by tracking used signatures or including per-address nonces

Answer

A replay attack reuses a valid signature to call mint() repeatedly; the fix is to record signatures in a mapping after first use or to embed a nonce in the signed message that is incremented and validated on-chain.

Question 4

How should an NFT contract correctly enforce per-address mint limits during a presale?

Accepted Answer

Maintain a mapping(address => uint256) on-chain that records how many tokens each address has minted, checked and updated atomically with the mint

Answer

A mapping(address => uint256) updated inside the mint function atomically records each address's usage, allowing the contract to revert if the caller exceeds their allowed quantity.

Question 5

Which built-in Ethereum function is used in Solidity to recover the signing address from an ECDSA signature?

Accepted Answer

ecrecover(bytes32 hash, uint8 v, bytes32 r, bytes32 s)

Answer

ecrecover() is an Ethereum precompile that accepts a message hash and the three signature components (v, r, s) and returns the Ethereum address whose private key produced that signature.

NFT Development Practice Test

NFT Development Practice Test

NFT Allowlist and Presale Mechanics 2