Bitcoin Transactions and Mining Flashcards

How is the fee of a standard Bitcoin transaction determined?

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

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

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

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

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

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

Answer: 100

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

How is a Bitcoin transaction ID (TXID) generated?

Answer: Double SHA-256 hash of the serialized transaction data

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

What does the nLockTime field in a Bitcoin transaction control?

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

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

Which blockchain analysis heuristic assumes that all inputs of a single transaction are controlled by the same entity?

Answer: Common-input-ownership heuristic

Because each input requires a valid signature, analysts assume co-spent inputs share an owner, enabling address clustering.

In what unit are Bitcoin fee rates typically expressed today?

Answer: Satoshis per virtual byte (sat/vB)

Miners prioritize transactions by fee per virtual byte, since block space is the scarce resource.