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Consensus Mechanisms Flashcards

7 cards from real CBCP 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. In Delegated Proof of Stake (DPoS), what is the primary role of 'witnesses' or 'delegates'?

    Answer: To produce blocks on behalf of token holders who voted for them

    In DPoS, token holders vote for delegates/witnesses who are then responsible for block production, making the system more democratic yet efficient.

  2. What distinguishes Byzantine Fault Tolerance (BFT) from Crash Fault Tolerance (CFT)?

    Answer: BFT can handle malicious or arbitrary node behavior, CFT only handles node crashes

    BFT tolerates nodes that act maliciously or send conflicting messages, while CFT only handles nodes that simply stop responding (crash).

  3. What is the 'nothing-at-stake' problem in early Proof of Stake designs?

    Answer: Validators can vote on multiple blockchain forks simultaneously with no cost

    Without a cost to validate multiple forks, validators in naive PoS could support all competing chains simultaneously, undermining consensus security.

  4. In the Tendermint consensus protocol, what happens if a validator fails to receive enough pre-commit messages?

    Answer: The round times out and a new round begins with a potential new proposer

    Tendermint uses rounds; if a block cannot gather sufficient pre-commits, the protocol moves to a new round where a different validator may propose a block.

  5. Which consensus mechanism does Hyperledger Fabric primarily use in its ordering service?

    Answer: Crash Fault Tolerant ordering (e.g., Raft)

    Hyperledger Fabric's ordering service uses CFT protocols like Raft by default, suitable for permissioned enterprise environments where Byzantine faults are less of a concern.

  6. What is 'slashing' in the context of Proof of Stake consensus?

    Answer: Penalizing validators by destroying a portion of their stake for provably malicious behavior

    Slashing is a punitive mechanism where validators who double-sign or behave maliciously lose part or all of their staked tokens as an economic deterrent.

  7. In Proof of Elapsed Time (PoET), what hardware feature is required to ensure fairness?

    Answer: Trusted Execution Environment (TEE) such as Intel SGX

    PoET relies on a TEE like Intel SGX to ensure that each node genuinely waits a randomly assigned time before claiming the right to create a block.