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Bitcoin Mining and Consensus Mechanisms Flashcards

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  1. What is 'merge mining' (AuxPoW) in the Bitcoin ecosystem?

    Answer: Mining a secondary blockchain using Bitcoin's proof-of-work with no extra computation

    Merge mining (Auxiliary Proof of Work) allows miners to submit Bitcoin's proof-of-work as valid proof for another blockchain that has adopted the same algorithm, at no additional computational cost.

  2. What is the maximum size of the nonce field in a Bitcoin block header?

    Answer: 32 bits

    The nonce is a 32-bit (4-byte) field in the block header, providing 2^32 (about 4.3 billion) possible values.

  3. What is a '51% attack' on the Bitcoin network?

    Answer: An entity controlling majority hashrate double-spends coins by rewriting recent history

    With over 50% of the network's hashrate, an attacker can mine a longer private chain to reverse recently confirmed transactions and double-spend bitcoin.

  4. What does the 'bits' field in a Bitcoin block header represent?

    Answer: The current difficulty target encoded in compact 4-byte format

    The 'bits' field is a compact encoding of the 256-bit difficulty target that a valid block hash must be less than or equal to.

  5. Why is Bitcoin's Proof of Work considered 'Nakamoto consensus'?

    Answer: Because it achieves agreement probabilistically through the longest valid chain rule without trusted parties

    Nakamoto consensus achieves decentralized agreement by having all nodes follow the chain with the most cumulative proof of work, without any central coordinator.

  6. What is the 'block withholding attack' in the context of mining pools?

    Answer: A miner submits only partial proofs-of-work and discards any full solutions it finds

    In a block withholding attack, a malicious miner submits valid shares (partial PoW) to collect pool earnings but secretly discards any full block solutions, sabotaging the pool's block-finding rate.

  7. Approximately how many bitcoin will ever be created in total?

    Answer: 21 million

    Bitcoin's supply is hard-capped at approximately 21 million BTC due to the halving schedule, with the last satoshi expected to be mined around the year 2140.