Bitcoin Mining and Consensus Flashcards

What is the primary purpose of the nonce field in a Bitcoin block header?

Answer: To provide a value miners iterate over to find a valid hash

Miners increment the nonce repeatedly until the block header hash meets the difficulty target.

What happens to the Bitcoin block subsidy approximately every 210,000 blocks?

Answer: It is cut in half

The halving event cuts the block subsidy in half roughly every four years, reducing new coin issuance.

Which consensus rule determines which chain Bitcoin nodes consider valid when two chains of equal length exist?

Answer: The chain with the most accumulated proof-of-work

Bitcoin nodes follow the chain with the greatest cumulative proof-of-work, often called the 'heaviest' chain.

What is an 'orphan block' in Bitcoin mining?

Answer: A valid block that is not part of the main chain because another block won the race

Orphan blocks are valid blocks that were not selected as part of the longest chain when two miners solved a block simultaneously.

What is the significance of the 'extraNonce' field used by miners?

Answer: It extends the nonce search space within the coinbase transaction

Since the 32-bit nonce space exhausts quickly, miners use the extraNonce in the coinbase to expand their search space.

Which of the following best describes 'selfish mining'?

Answer: Withholding discovered blocks to gain a competitive advantage over honest miners

Selfish mining is a strategy where a pool withholds valid blocks to waste honest miners' effort and earn a disproportionate share of rewards.

What is the target block interval Bitcoin's difficulty adjustment aims to maintain?

Answer: 10 minutes

Bitcoin's protocol is designed to produce a new block approximately every 10 minutes on average.