Consensus Mechanisms and Mining Flashcards
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Read the first 7 Consensus Mechanisms and Mining flashcards as text
What is the key difference between 'probabilistic finality' and 'deterministic finality' in blockchain consensus?
Answer: Probabilistic finality means reversals become increasingly unlikely over time; deterministic finality means a committed block cannot be reversed
PoW chains like Bitcoin have probabilistic finality where deep confirmations make reversal impractical, while BFT-based PoS systems provide absolute finality once a block is committed.
What is the role of 'validators' in a Proof of Stake network compared to 'miners' in Proof of Work?
Answer: Validators lock up cryptocurrency as collateral to propose and attest to blocks instead of expending computational energy
PoS validators stake ETH or other tokens as economic collateral and take turns proposing/attesting to blocks, replacing the energy-intensive hash competition of PoW miners.
In the PBFT (Practical Byzantine Fault Tolerance) algorithm, what is the minimum number of nodes required to tolerate f Byzantine faulty nodes?
Answer: 3f + 1
PBFT requires at least 3f + 1 total nodes to tolerate f Byzantine failures, ensuring a two-thirds majority of honest nodes for safe consensus.
What is 'long-range attack' in Proof of Stake systems, and what is the common defense?
Answer: An attack where old private keys are used to rewrite history from a distant checkpoint; defended by weak subjectivity checkpoints
Long-range attacks use old validator keys (possibly sold or compromised) to fork the chain from a past point; weak subjectivity requires nodes to trust a recent checkpoint when syncing.
Which consensus mechanism does Solana use to achieve its high throughput?
Answer: Proof of History combined with Tower BFT
Solana uses Proof of History (a verifiable delay function creating a cryptographic clock) combined with Tower BFT to achieve consensus without requiring nodes to communicate timestamps.
What is 'uncle blocks' (ommer blocks) in Ethereum's original PoW consensus?
Answer: Valid blocks discovered simultaneously with the winning block that are included for partial rewards
Uncle blocks are valid PoW solutions found at the same time as a winning block; Ethereum included them in the chain and rewarded their miners to reduce centralization pressure from stale blocks.
In the context of blockchain mining, what does 'hashrate' measure?
Answer: The number of hash computations a miner performs per second
Hashrate is the computational speed of a mining operation, measured in hashes per second (H/s), indicating how many proof-of-work attempts can be made each second.