CCA Transactions & Verification 2

Question 1

In a Bitcoin UTXO model, what happens when a transaction output is partially spent?

Accepted Answer

A new change UTXO is created and sent back to the sender

Answer

Bitcoin transactions consume entire UTXOs; any leftover amount is returned to the sender as a new change output (UTXO).

Question 2

Which script type is used in standard Bitcoin Pay-to-Public-Key-Hash (P2PKH) transactions?

Accepted Answer

Legacy scriptPubKey with OP_DUP OP_HASH160

Answer

P2PKH locking scripts use OP_DUP OP_HASH160 followed by the hash of the public key and OP_EQUALVERIFY OP_CHECKSIG.

Question 3

What is a Replace-By-Fee (RBF) transaction and its primary audit concern?

Accepted Answer

A mechanism to replace an unconfirmed transaction with a higher fee; concern is double-spend risk

Answer

RBF allows rebroadcasting an unconfirmed transaction with a higher fee, raising double-spend concerns before the original confirms.

Question 4

In Ethereum, what is the role of the 'nonce' field in a transaction?

Accepted Answer

It prevents replay attacks and ensures transaction ordering per account

Answer

The nonce is a sequential counter per Ethereum account that prevents replay attacks and enforces strict ordering of transactions.

Question 5

Which hashing algorithm does Bitcoin use to generate a transaction ID (TXID)?

Accepted Answer

SHA-256 applied twice (double SHA-256)

Answer

Bitcoin TXIDs are computed by applying SHA-256 twice (SHA-256d) to the serialized transaction data.

(CCA) Certified Cryptocurrency Auditor Practice Test