CBP Blockchain and Transaction Mechanics 2

Question 1

What is the purpose of the nLockTime field in a Bitcoin transaction?

Accepted Answer

It specifies the earliest block height or timestamp at which the transaction can be mined

Answer

nLockTime specifies the earliest block height or Unix timestamp before which the transaction cannot be included in a block.

Question 2

In a Bitcoin transaction, what does the sequence number field on each input control when nLockTime is used?

Accepted Answer

Whether the input opts into RBF (Replace-By-Fee)

Answer

An input with a sequence number below 0xFFFFFFFE signals RBF opt-in and also allows nLockTime to be enforced.

Question 3

What is the maximum size of a standard Bitcoin block introduced by the SegWit upgrade (in weight units)?

Accepted Answer

4,000,000 weight units

Answer

SegWit replaced the 1 MB byte limit with a 4,000,000 weight unit limit, where witness data is discounted to 1/4 weight.

Question 4

Which hashing algorithm does Bitcoin use to produce a block's Proof-of-Work?

Accepted Answer

SHA-256 applied twice (double-SHA-256)

Answer

Bitcoin's Proof-of-Work hashes the block header using double-SHA-256 (SHA-256 applied twice) to find a hash below the target.

Question 5

What information is stored in the coinbase transaction of a Bitcoin block?

Accepted Answer

The block reward plus fees, and an arbitrary data field (up to 100 bytes)

Answer

The coinbase transaction creates new bitcoin (block subsidy + fees) and contains an arbitrary data field miners can use for extra nonce space or tagging.

(CBP) Certified Bitcoin Professional Practice Test

(CBP) Certified Bitcoin Professional Practice Test

CBP Blockchain and Transaction Mechanics 2