CCI Bitcoin Transactions and Mining 2

Question 1

How is the fee of a standard Bitcoin transaction determined?

Accepted Answer

It is the total value of inputs minus the total value of outputs

Answer

Bitcoin has no explicit fee field; any input value not assigned to outputs is claimed by the miner as the fee.

Question 2

A suspect spends a 2 BTC UTXO to pay 0.4 BTC to a merchant. What normally happens to the remaining value?

Accepted Answer

It is sent to a change output controlled by the sender, minus the fee

Answer

UTXOs must be spent in full, so wallets create a change output back to the sender for the excess.

Question 3

How many blocks must pass before newly mined coins from a coinbase transaction can be spent?

Accepted Answer

100

Answer

Coinbase outputs have a 100-block maturity rule to protect against chain reorganizations.

Question 4

How is a Bitcoin transaction ID (TXID) generated?

Accepted Answer

Double SHA-256 hash of the serialized transaction data

Answer

A TXID is the double SHA-256 hash of the transaction (excluding witness data for SegWit transactions).

Question 5

What does the nLockTime field in a Bitcoin transaction control?

Accepted Answer

The earliest block height or time at which the transaction can be included in a block

Answer

nLockTime prevents a transaction from being mined until a specified block height or Unix timestamp.

CCI - Certified Cryptocurrency Investigator Practice Test