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Blockchain and Consensus Mechanisms Flashcards

7 cards from real Cryptocurrency practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.

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  1. What is a 'genesis block' in a blockchain?

    Answer: The very first block in a blockchain, with no predecessor

    The genesis block is block zero — hardcoded into the protocol, it has no parent hash and anchors the entire chain.

  2. What is the purpose of the 'difficulty adjustment' mechanism in Bitcoin?

    Answer: To keep the average block time near 10 minutes regardless of total hash rate

    Bitcoin recalibrates mining difficulty every 2,016 blocks so that blocks are produced approximately every 10 minutes even as hash rate fluctuates.

  3. In Ethereum's proof-of-stake, what is an 'epoch'?

    Answer: A period of 32 slots used to organize validator duties and finalization checkpoints

    An epoch consists of 32 slots (approximately 6.4 minutes total), after which the beacon chain processes validator shuffling and finalization.

  4. What is a 'light client' in blockchain terminology?

    Answer: A node that downloads only block headers to verify state without storing the full chain

    Light clients use Merkle proofs and block headers to verify transactions without downloading the full blockchain, reducing resource requirements.

  5. What is the CAP theorem's relevance to blockchain design?

    Answer: It states a distributed system cannot simultaneously guarantee consistency, availability, and partition tolerance

    The CAP theorem forces blockchain designers to trade off between consistency and availability during network partitions, influencing consensus design choices.

  6. What is 'selfish mining' as a blockchain attack strategy?

    Answer: Mining blocks privately and revealing them strategically to waste honest miners' work

    Selfish mining involves withholding discovered blocks and releasing them at strategic moments to invalidate honest miners' work and earn a disproportionate share of rewards.

  7. What does 'sharding' aim to solve in blockchain scalability?

    Answer: It splits the blockchain into parallel sub-chains so nodes only process a subset of transactions

    Sharding partitions the network's workload across multiple shards, each processing its own transactions in parallel, increasing overall throughput.