Blockchain Developer Consensus Mechanisms 2 — Questions and Answers
Question 1: In Proof of Stake, what does 'slashing' refer to?
- Reducing block size
- Penalizing a validator by destroying part of its staked funds (Correct answer)
- Halving the block reward
- Compressing transaction data
Correct answer: Penalizing a validator by destroying part of its staked funds
Slashing destroys a portion of a validator's stake as punishment for malicious or faulty behavior.
Question 2: What problem does the 'nothing-at-stake' issue describe in PoS systems?
- Validators have no incentive to validate multiple competing chains
- Validators can vote on every fork at no cost (Correct answer)
- Miners abandon the network
- Nodes run out of storage
Correct answer: Validators can vote on every fork at no cost
Without penalties, validators can cheaply support multiple competing forks, undermining consensus.
Question 3: Which consensus mechanism does Solana combine with Proof of Stake to order transactions?
- Proof of History (Correct answer)
- Proof of Authority
- Proof of Burn
- Proof of Capacity
Correct answer: Proof of History
Solana uses Proof of History as a cryptographic clock to timestamp and order events before PoS finalization.
Question 4: In Delegated Proof of Stake (DPoS), how are block producers chosen?
- By raw hashing power
- By token holders voting for delegates (Correct answer)
- By random VRF only
- By transaction fees paid
Correct answer: By token holders voting for delegates
DPoS lets token holders vote to elect a limited set of delegates who produce blocks.
Question 5: What is the primary purpose of a 'finality gadget' like Casper FFG?
- To increase block size
- To provide checkpoints that make blocks irreversible (Correct answer)
- To compress the state trie
- To distribute mining rewards
Correct answer: To provide checkpoints that make blocks irreversible
Finality gadgets finalize checkpoints so that finalized blocks cannot be reverted without major economic loss.
Question 6: In a Byzantine Fault Tolerant system tolerating f faulty nodes, what is the minimum total number of nodes required?
- 2f + 1
- 3f + 1 (Correct answer)
- f + 1
- 4f
Correct answer: 3f + 1
Classical BFT consensus requires at least 3f + 1 nodes to tolerate f Byzantine faults.
Question 7: What does 'weak subjectivity' mean in Proof of Stake networks?
- Nodes need a recent trusted checkpoint to sync safely (Correct answer)
- Validators can be chosen subjectively by the founder
- Blocks have no fixed time
- Staking is optional
Correct answer: Nodes need a recent trusted checkpoint to sync safely
New or long-offline nodes must rely on a recent trusted checkpoint to avoid long-range attacks.
Blockchain Developer Consensus Mechanisms 2
In Proof of Stake, what does 'slashing' refer to?