CBCP Consensus Mechanisms 2 — Questions and Answers
Question 1: In Delegated Proof of Stake (DPoS), what is the primary role of 'witnesses' or 'delegates'?
- To audit smart contract code
- To produce blocks on behalf of token holders who voted for them (Correct answer)
- To hold reserve funds for network security
- To validate identity of new participants
Correct 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.
Question 2: What distinguishes Byzantine Fault Tolerance (BFT) from Crash Fault Tolerance (CFT)?
- BFT only works in permissioned networks
- BFT can handle malicious or arbitrary node behavior, CFT only handles node crashes (Correct answer)
- CFT requires more nodes to achieve consensus
- BFT always requires more than 50% honest nodes
Correct 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).
Question 3: What is the 'nothing-at-stake' problem in early Proof of Stake designs?
- Validators earn no rewards for honest behavior
- Validators can vote on multiple blockchain forks simultaneously with no cost (Correct answer)
- Staking rewards are insufficient to attract validators
- New validators have no stake in the network's success
Correct 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.
Question 4: In the Tendermint consensus protocol, what happens if a validator fails to receive enough pre-commit messages?
- The block is automatically accepted after a timeout
- The round times out and a new round begins with a potential new proposer (Correct answer)
- The validator is immediately slashed
- Consensus falls back to Proof of Work
Correct 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.
Question 5: Which consensus mechanism does Hyperledger Fabric primarily use in its ordering service?
- Proof of Work
- Proof of Authority with mining
- Crash Fault Tolerant ordering (e.g., Raft) (Correct answer)
- Delegated Proof of Stake
Correct 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.
Question 6: What is 'slashing' in the context of Proof of Stake consensus?
- Reducing block rewards during network congestion
- Penalizing validators by destroying a portion of their stake for provably malicious behavior (Correct answer)
- Removing inactive validators from the validator set
- Cutting transaction fees to zero temporarily
Correct 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.
Question 7: In Proof of Elapsed Time (PoET), what hardware feature is required to ensure fairness?
- GPU with hardware random number generation
- Trusted Execution Environment (TEE) such as Intel SGX (Correct answer)
- Hardware Security Module (HSM) for key storage
- ASIC chips with verified firmware
Correct 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.
CBCP Consensus Mechanisms 2
In Delegated Proof of Stake (DPoS), what is the primary role of 'witnesses' or 'delegates'?