CBP Bitcoin Mining and Consensus 3 — Questions and Answers
Question 1: What information is stored in a Bitcoin block header?
- All transaction data, miner identity, and block reward
- Version, previous block hash, merkle root, timestamp, bits, and nonce (Correct answer)
- Sender addresses, receiver addresses, and amounts only
- Public keys of all transaction participants
Correct answer: Version, previous block hash, merkle root, timestamp, bits, and nonce
The 80-byte block header contains version, previous block hash, merkle root, timestamp, difficulty bits, and nonce.
Question 2: In Bitcoin mining pools, what does 'vardiff' refer to?
- Variable transaction fees based on mempool congestion
- Dynamic share difficulty adjusted to a miner's hash rate (Correct answer)
- The variance in block reward between halvings
- Fluctuating network difficulty between adjustment periods
Correct answer: Dynamic share difficulty adjusted to a miner's hash rate
Vardiff automatically adjusts the difficulty of shares submitted by a miner to match their hash rate, keeping submission rates efficient.
Question 3: What does the 'merkle root' in a block header represent?
- The hash of the previous block
- A single hash summarizing all transactions in the block (Correct answer)
- The miner's public key
- The coinbase transaction hash
Correct answer: A single hash summarizing all transactions in the block
The merkle root is the root hash of a binary hash tree built from all transaction IDs in the block.
Question 4: What is a 'share' in the context of pooled mining?
- A fraction of a Bitcoin sent as a fee
- A proof-of-work result that meets the pool's lower difficulty target (Correct answer)
- A smart contract governing pool payouts
- A miner's percentage stake in the pool's hardware
Correct answer: A proof-of-work result that meets the pool's lower difficulty target
Shares are partial proof-of-work results that prove a miner is working, used by pools to allocate rewards proportionally.
Question 5: What is 'merge mining'?
- Combining multiple ASIC devices into a single mining unit
- Mining two or more cryptocurrencies simultaneously using the same proof-of-work (Correct answer)
- Merging two mining pools into a single entity
- Running Bitcoin and Litecoin nodes on the same server
Correct answer: Mining two or more cryptocurrencies simultaneously using the same proof-of-work
Merge mining allows miners to simultaneously mine Bitcoin and an auxiliary chain like Namecoin with no extra computational cost.
Question 6: How does Bitcoin prevent a miner from backdating a block's timestamp significantly?
- GPS synchronization is required for all mining nodes
- Nodes reject blocks with timestamps more than 2 hours in the future or earlier than the median of the last 11 blocks (Correct answer)
- The timestamp must match UTC to the second
- A third-party time authority signs each block
Correct answer: Nodes reject blocks with timestamps more than 2 hours in the future or earlier than the median of the last 11 blocks
Bitcoin enforces a median-time-past rule and a 2-hour future limit to prevent extreme timestamp manipulation.
Question 7: What is the maximum size of a Bitcoin block under the original pre-SegWit rules?
- 512 KB
- 1 MB (Correct answer)
- 2 MB
- 4 MB
Correct answer: 1 MB
The original Bitcoin block size limit was 1 megabyte, introduced to prevent spam attacks on the network.
CBP Bitcoin Mining and Consensus 3
What information is stored in a Bitcoin block header?